Module java.base
Package java.lang.invoke

Class VarHandle

  • public abstract classVarHandleextendsObject
    A VarHandle is a dynamically strongly typed reference to a variable, or to a parametrically-defined family of variables, including static fields, non-static fields, array elements, or components of an off-heap data structure. Access to such variables is supported under variousaccess modes, including plain read/write access, volatile read/write access, and compare-and-set.

    VarHandles are immutable and have no visible state. VarHandles cannot be subclassed by the user.

    A VarHandle has:

    • avariable type T, the type of every variable referenced by this VarHandle; and
    • a list ofcoordinate typesCT1, CT2, ..., CTn, the types ofcoordinate expressions that jointly locate a variable referenced by this VarHandle.
    Variable and coordinate types may be primitive or reference, and are represented byClass objects. The list of coordinate types may be empty.

    Factory methods that produce orlookup VarHandle instances document the supported variable type and the list of coordinate types.

    Each access mode is associated with oneaccess mode method, asignature polymorphic method named for the access mode. When an access mode method is invoked on a VarHandle instance, the initial arguments to the invocation are coordinate expressions that indicate in precisely which object the variable is to be accessed. Trailing arguments to the invocation represent values of importance to the access mode. For example, the various compare-and-set or compare-and-exchange access modes require two trailing arguments for the variable's expected value and new value.

    The arity and types of arguments to the invocation of an access mode method are not checked statically. Instead, each access mode method specifies anaccess mode type, represented as an instance ofMethodType, that serves as a kind of method signature against which the arguments are checked dynamically. An access mode type gives formal parameter types in terms of the coordinate types of a VarHandle instance and the types for values of importance to the access mode. An access mode type also gives a return type, often in terms of the variable type of a VarHandle instance. When an access mode method is invoked on a VarHandle instance, the symbolic type descriptor at the call site, the run time types of arguments to the invocation, and the run time type of the return value, mustmatch the types given in the access mode type. A runtime exception will be thrown if the match fails. For example, the access mode methodcompareAndSet(java.lang.Object...) specifies that if its receiver is a VarHandle instance with coordinate typesCT1, ..., CTn and variable typeT, then its access mode type is(CT1 c1, ..., CTn cn, T expectedValue, T newValue)boolean. Suppose that a VarHandle instance can access array elements, and that its coordinate types areString[] andint while its variable type isString. The access mode type forcompareAndSet on this VarHandle instance would be(String[] c1, int c2, String expectedValue, String newValue)boolean. Such a VarHandle instance may be produced by thearray factory method and access array elements as follows:

     String[] sa = ... VarHandle avh = MethodHandles.arrayElementVarHandle(String[].class); boolean r = avh.compareAndSet(sa, 10, "expected", "new");

    Access modes control atomicity and consistency properties.Plain read (get) and write (set) accesses are guaranteed to be bitwise atomic only for references and for primitive values of at most 32 bits, and impose no observable ordering constraints with respect to threads other than the executing thread.Opaque operations are bitwise atomic and coherently ordered with respect to accesses to the same variable. In addition to obeying Opaque properties,Acquire mode reads and their subsequent accesses are ordered after matchingRelease mode writes and their previous accesses. In addition to obeying Acquire and Release properties, allVolatile operations are totally ordered with respect to each other.

    Access modes are grouped into the following categories:

    Factory methods that produce orlookup VarHandle instances document the set of access modes that are supported, which may also include documenting restrictions based on the variable type and whether a variable is read-only. If an access mode is not supported then the corresponding access mode method will on invocation throw anUnsupportedOperationException. Factory methods should document any additional undeclared exceptions that may be thrown by access mode methods. Theget access mode is supported for all VarHandle instances and the corresponding method never throwsUnsupportedOperationException. If a VarHandle references a read-only variable (for example afinal field) then write, atomic update, numeric atomic update, and bitwise atomic update access modes are not supported and corresponding methods throwUnsupportedOperationException. Read/write access modes (if supported), with the exception ofget andset, provide atomic access for reference types and all primitive types. Unless stated otherwise in the documentation of a factory method, the access modesget andset (if supported) provide atomic access for reference types and all primitives types, with the exception oflong anddouble on 32-bit platforms.

    Access modes will override any memory ordering effects specified at the declaration site of a variable. For example, a VarHandle accessing a field using theget access mode will access the field as specifiedby its access mode even if that field is declaredvolatile. When mixed access is performed extreme care should be taken since the Java Memory Model may permit surprising results.

    In addition to supporting access to variables under various access modes, a set of static methods, referred to as memory fence methods, is also provided for fine-grained control of memory ordering. The Java Language Specification permits other threads to observe operations as if they were executed in orders different than are apparent in program source code, subject to constraints arising, for example, from the use of locks,volatile fields or VarHandles. The static methods,fullFence,acquireFence,releaseFence,loadLoadFence andstoreStoreFence, can also be used to impose constraints. Their specifications, as is the case for certain access modes, are phrased in terms of the lack of "reorderings" -- observable ordering effects that might otherwise occur if the fence was not present. More precise phrasing of the specification of access mode methods and memory fence methods may accompany future updates of the Java Language Specification.

    Compiling invocation of access mode methods

    A Java method call expression naming an access mode method can invoke a VarHandle from Java source code. From the viewpoint of source code, these methods can take any arguments and their polymorphic result (if expressed) can be cast to any return type. Formally this is accomplished by giving the access mode methods variable arityObject arguments andObject return types (if the return type is polymorphic), but they have an additional quality calledsignature polymorphism which connects this freedom of invocation directly to the JVM execution stack.

    As is usual with virtual methods, source-level calls to access mode methods compile to aninvokevirtual instruction. More unusually, the compiler must record the actual argument types, and may not perform method invocation conversions on the arguments. Instead, it must generate instructions to push them on the stack according to their own unconverted types. The VarHandle object itself will be pushed on the stack before the arguments. The compiler then generates aninvokevirtual instruction that invokes the access mode method with a symbolic type descriptor which describes the argument and return types.

    To issue a complete symbolic type descriptor, the compiler must also determine the return type (if polymorphic). This is based on a cast on the method invocation expression, if there is one, or elseObject if the invocation is an expression, or elsevoid if the invocation is a statement. The cast may be to a primitive type (but notvoid).

    As a corner case, an uncastednull argument is given a symbolic type descriptor ofjava.lang.Void. The ambiguity with the typeVoid is harmless, since there are no references of typeVoid except the null reference.

    Performing invocation of access mode methods

    The first time aninvokevirtual instruction is executed it is linked by symbolically resolving the names in the instruction and verifying that the method call is statically legal. This also holds for calls to access mode methods. In this case, the symbolic type descriptor emitted by the compiler is checked for correct syntax, and names it contains are resolved. Thus, aninvokevirtual instruction which invokes an access mode method will always link, as long as the symbolic type descriptor is syntactically well-formed and the types exist.

    When theinvokevirtual is executed after linking, the receiving VarHandle's access mode type is first checked by the JVM to ensure that it matches the symbolic type descriptor. If the type match fails, it means that the access mode method which the caller is invoking is not present on the individual VarHandle being invoked.

    Invocation of an access mode method behaves as if an invocation ofMethodHandle.invoke(java.lang.Object...), where the receiving method handle accepts the VarHandle instance as the leading argument. More specifically, the following, where{access-mode} corresponds to the access mode method name:

     VarHandle vh = .. R r = (R) vh.{access-mode}(p1, p2, ..., pN);
    behaves as if:
     VarHandle vh = .. VarHandle.AccessMode am = VarHandle.AccessMode.valueFromMethodName("{access-mode}"); MethodHandle mh = MethodHandles.varHandleExactInvoker(                       am,                       vh.accessModeType(am)); R r = (R) mh.invoke(vh, p1, p2, ..., pN)
    (modulo access mode methods do not declare throwing ofThrowable). This is equivalent to:
     MethodHandle mh = MethodHandles.lookup().findVirtual(                       VarHandle.class,                       "{access-mode}",                       MethodType.methodType(R, p1, p2, ..., pN)); R r = (R) mh.invokeExact(vh, p1, p2, ..., pN)
    where the desired method type is the symbolic type descriptor and aMethodHandle.invokeExact(java.lang.Object...) is performed, since before invocation of the target, the handle will apply reference casts as necessary and box, unbox, or widen primitive values, as if byasType (see alsoMethodHandles.varHandleInvoker(java.lang.invoke.VarHandle.AccessMode, java.lang.invoke.MethodType)). More concisely, such behaviour is equivalent to:
     VarHandle vh = .. VarHandle.AccessMode am = VarHandle.AccessMode.valueFromMethodName("{access-mode}"); MethodHandle mh = vh.toMethodHandle(am); R r = (R) mh.invoke(p1, p2, ..., pN)
    Where, in this case, the method handle is bound to the VarHandle instance.

    Invocation checking

    In typical programs, VarHandle access mode type matching will usually succeed. But if a match fails, the JVM will throw aWrongMethodTypeException.

    Thus, an access mode type mismatch which might show up as a linkage error in a statically typed program can show up as a dynamicWrongMethodTypeException in a program which uses VarHandles.

    Because access mode types contain "live"Class objects, method type matching takes into account both type names and class loaders. Thus, even if a VarHandleVH is created in one class loaderL1 and used in anotherL2, VarHandle access mode method calls are type-safe, because the caller's symbolic type descriptor, as resolved inL2, is matched against the original callee method's symbolic type descriptor, as resolved inL1. The resolution inL1 happens whenVH is created and its access mode types are assigned, while the resolution inL2 happens when theinvokevirtual instruction is linked.

    Apart from type descriptor checks, a VarHandles's capability to access it's variables is unrestricted. If a VarHandle is formed on a non-public variable by a class that has access to that variable, the resulting VarHandle can be used in any place by any caller who receives a reference to it.

    Unlike with the Core Reflection API, where access is checked every time a reflective method is invoked, VarHandle access checking is performedwhen the VarHandle is created. Thus, VarHandles to non-public variables, or to variables in non-public classes, should generally be kept secret. They should not be passed to untrusted code unless their use from the untrusted code would be harmless.

    VarHandle creation

    Java code can create a VarHandle that directly accesses any field that is accessible to that code. This is done via a reflective, capability-based API calledMethodHandles.Lookup. For example, a VarHandle for a non-static field can be obtained fromLookup.findVarHandle. There is also a conversion method from Core Reflection API objects,Lookup.unreflectVarHandle.

    Access to protected field members is restricted to receivers only of the accessing class, or one of its subclasses, and the accessing class must in turn be a subclass (or package sibling) of the protected member's defining class. If a VarHandle refers to a protected non-static field of a declaring class outside the current package, the receiver argument will be narrowed to the type of the accessing class.

    Interoperation between VarHandles and the Core Reflection API

    Using factory methods in theLookup API, any field represented by a Core Reflection API object can be converted to a behaviorally equivalent VarHandle. For example, a reflectiveField can be converted to a VarHandle usingLookup.unreflectVarHandle. The resulting VarHandles generally provide more direct and efficient access to the underlying fields.

    As a special case, when the Core Reflection API is used to view the signature polymorphic access mode methods in this class, they appear as ordinary non-polymorphic methods. Their reflective appearance, as viewed byClass.getDeclaredMethod, is unaffected by their special status in this API. For example,Method.getModifiers will report exactly those modifier bits required for any similarly declared method, including in this casenative andvarargs bits.

    As with any reflected method, these methods (when reflected) may be invoked directly viajava.lang.reflect.Method.invoke, via JNI, or indirectly viaLookup.unreflect. However, such reflective calls do not result in access mode method invocations. Such a call, if passed the required argument (a single one, of typeObject[]), will ignore the argument and will throw anUnsupportedOperationException.

    Sinceinvokevirtual instructions can natively invoke VarHandle access mode methods under any symbolic type descriptor, this reflective view conflicts with the normal presentation of these methods via bytecodes. Thus, these native methods, when reflectively viewed byClass.getDeclaredMethod, may be regarded as placeholders only.

    In order to obtain an invoker method for a particular access mode type, useMethodHandles.varHandleExactInvoker(java.lang.invoke.VarHandle.AccessMode, java.lang.invoke.MethodType) orMethodHandles.varHandleInvoker(java.lang.invoke.VarHandle.AccessMode, java.lang.invoke.MethodType). TheLookup.findVirtual API is also able to return a method handle to call an access mode method for any specified access mode type and is equivalent in behaviour toMethodHandles.varHandleInvoker(java.lang.invoke.VarHandle.AccessMode, java.lang.invoke.MethodType).

    Interoperation between VarHandles and Java generics

    A VarHandle can be obtained for a variable, such as a field, which is declared with Java generic types. As with the Core Reflection API, the VarHandle's variable type will be constructed from the erasure of the source-level type. When a VarHandle access mode method is invoked, the types of its arguments or the return value cast type may be generic types or type instances. If this occurs, the compiler will replace those types by their erasures when it constructs the symbolic type descriptor for theinvokevirtual instruction.
    Since:
    9
    See Also:
    MethodHandle,MethodHandles,MethodType

    • Method Detail

      • get

        public final Object get​(Object... args)
        Returns the value of a variable, with memory semantics of reading as if the variable was declared non-volatile. Commonly referred to as plain read access.

        The method signature is of the form(CT1 ct1, ..., CTn ctn)T.

        The symbolic type descriptor at the call site ofget must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET) on this VarHandle.

        This access mode is supported by all VarHandle instances and never throwsUnsupportedOperationException.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn) , statically represented using varargs.
        Returns:
        the signature-polymorphic result that is the value of the variable , statically represented usingObject.
        Throws:
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.

      • set

        public final void set​(Object... args)
        Sets the value of a variable to thenewValue, with memory semantics of setting as if the variable was declared non-volatile and non-final. Commonly referred to as plain write access.

        The method signature is of the form(CT1 ct1, ..., CTn ctn, T newValue)void

        The symbolic type descriptor at the call site ofset must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.SET) on this VarHandle.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T newValue) , statically represented using varargs.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.

      • getVolatile

        public final Object getVolatile​(Object... args)
        Returns the value of a variable, with memory semantics of reading as if the variable was declaredvolatile.

        The method signature is of the form(CT1 ct1, ..., CTn ctn)T.

        The symbolic type descriptor at the call site ofgetVolatile must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_VOLATILE) on this VarHandle.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn) , statically represented using varargs.
        Returns:
        the signature-polymorphic result that is the value of the variable , statically represented usingObject.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.

      • setVolatile

        public final void setVolatile​(Object... args)
        Sets the value of a variable to thenewValue, with memory semantics of setting as if the variable was declaredvolatile.

        The method signature is of the form(CT1 ct1, ..., CTn ctn, T newValue)void.

        The symbolic type descriptor at the call site ofsetVolatile must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.SET_VOLATILE) on this VarHandle.

        API Note:
        Ignoring the many semantic differences from C and C++, this method has memory ordering effects compatible withmemory_order_seq_cst.
        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T newValue) , statically represented using varargs.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.

      • getOpaque

        public final Object getOpaque​(Object... args)
        Returns the value of a variable, accessed in program order, but with no assurance of memory ordering effects with respect to other threads.

        The method signature is of the form(CT1 ct1, ..., CTn ctn)T.

        The symbolic type descriptor at the call site ofgetOpaque must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_OPAQUE) on this VarHandle.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn) , statically represented using varargs.
        Returns:
        the signature-polymorphic result that is the value of the variable , statically represented usingObject.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.

      • setOpaque

        public final void setOpaque​(Object... args)
        Sets the value of a variable to thenewValue, in program order, but with no assurance of memory ordering effects with respect to other threads.

        The method signature is of the form(CT1 ct1, ..., CTn ctn, T newValue)void.

        The symbolic type descriptor at the call site ofsetOpaque must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.SET_OPAQUE) on this VarHandle.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T newValue) , statically represented using varargs.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.

      • getAcquire

        public final Object getAcquire​(Object... args)
        Returns the value of a variable, and ensures that subsequent loads and stores are not reordered before this access.

        The method signature is of the form(CT1 ct1, ..., CTn ctn)T.

        The symbolic type descriptor at the call site ofgetAcquire must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_ACQUIRE) on this VarHandle.

        API Note:
        Ignoring the many semantic differences from C and C++, this method has memory ordering effects compatible withmemory_order_acquire ordering.
        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn) , statically represented using varargs.
        Returns:
        the signature-polymorphic result that is the value of the variable , statically represented usingObject.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.

      • setRelease

        public final void setRelease​(Object... args)
        Sets the value of a variable to thenewValue, and ensures that prior loads and stores are not reordered after this access.

        The method signature is of the form(CT1 ct1, ..., CTn ctn, T newValue)void.

        The symbolic type descriptor at the call site ofsetRelease must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.SET_RELEASE) on this VarHandle.

        API Note:
        Ignoring the many semantic differences from C and C++, this method has memory ordering effects compatible withmemory_order_release ordering.
        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T newValue) , statically represented using varargs.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.

      • compareAndSet

        public final boolean compareAndSet​(Object... args)
        Atomically sets the value of a variable to thenewValue with the memory semantics ofsetVolatile(java.lang.Object...) if the variable's current value, referred to as thewitness value,== theexpectedValue, as accessed with the memory semantics ofgetVolatile(java.lang.Object...).

        The method signature is of the form(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)boolean.

        The symbolic type descriptor at the call site of compareAndSet must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.COMPARE_AND_SET) on this VarHandle.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue) , statically represented using varargs.
        Returns:
        true if successful, otherwisefalse if the witness value was not the same as theexpectedValue.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
        See Also:
        setVolatile(Object...),getVolatile(Object...)

      • compareAndExchange

        public final Object compareAndExchange​(Object... args)
        Atomically sets the value of a variable to thenewValue with the memory semantics ofsetVolatile(java.lang.Object...) if the variable's current value, referred to as thewitness value,== theexpectedValue, as accessed with the memory semantics ofgetVolatile(java.lang.Object...).

        The method signature is of the form(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)T.

        The symbolic type descriptor at the call site of compareAndExchange must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.COMPARE_AND_EXCHANGE) on this VarHandle.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue) , statically represented using varargs.
        Returns:
        the signature-polymorphic result that is the witness value, which will be the same as theexpectedValue if successful , statically represented usingObject.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type is not compatible with the caller's symbolic type descriptor.
        ClassCastException - if the access mode type is compatible with the caller's symbolic type descriptor, but a reference cast fails.
        See Also:
        setVolatile(Object...),getVolatile(Object...)

      • compareAndExchangeAcquire

        public final Object compareAndExchangeAcquire​(Object... args)
        Atomically sets the value of a variable to thenewValue with the memory semantics ofset(java.lang.Object...) if the variable's current value, referred to as thewitness value,== theexpectedValue, as accessed with the memory semantics ofgetAcquire(java.lang.Object...).

        The method signature is of the form(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)T.

        The symbolic type descriptor at the call site of compareAndExchangeAcquire must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.COMPARE_AND_EXCHANGE_ACQUIRE) on this VarHandle.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue) , statically represented using varargs.
        Returns:
        the signature-polymorphic result that is the witness value, which will be the same as theexpectedValue if successful , statically represented usingObject.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
        See Also:
        set(Object...),getAcquire(Object...)

      • compareAndExchangeRelease

        public final Object compareAndExchangeRelease​(Object... args)
        Atomically sets the value of a variable to thenewValue with the memory semantics ofsetRelease(java.lang.Object...) if the variable's current value, referred to as thewitness value,== theexpectedValue, as accessed with the memory semantics ofget(java.lang.Object...).

        The method signature is of the form(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)T.

        The symbolic type descriptor at the call site of compareAndExchangeRelease must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.COMPARE_AND_EXCHANGE_RELEASE) on this VarHandle.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue) , statically represented using varargs.
        Returns:
        the signature-polymorphic result that is the witness value, which will be the same as theexpectedValue if successful , statically represented usingObject.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
        See Also:
        setRelease(Object...),get(Object...)

      • weakCompareAndSetPlain

        public final boolean weakCompareAndSetPlain​(Object... args)
        Possibly atomically sets the value of a variable to thenewValue with the semantics ofset(java.lang.Object...) if the variable's current value, referred to as thewitness value,== theexpectedValue, as accessed with the memory semantics ofget(java.lang.Object...).

        This operation may fail spuriously (typically, due to memory contention) even if the witness value does match the expected value.

        The method signature is of the form(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)boolean.

        The symbolic type descriptor at the call site of weakCompareAndSetPlain must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.WEAK_COMPARE_AND_SET_PLAIN) on this VarHandle.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue) , statically represented using varargs.
        Returns:
        true if successful, otherwisefalse if the witness value was not the same as theexpectedValue or if this operation spuriously failed.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
        See Also:
        set(Object...),get(Object...)

      • weakCompareAndSet

        public final boolean weakCompareAndSet​(Object... args)
        Possibly atomically sets the value of a variable to thenewValue with the memory semantics ofsetVolatile(java.lang.Object...) if the variable's current value, referred to as thewitness value,== theexpectedValue, as accessed with the memory semantics ofgetVolatile(java.lang.Object...).

        This operation may fail spuriously (typically, due to memory contention) even if the witness value does match the expected value.

        The method signature is of the form(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)boolean.

        The symbolic type descriptor at the call site of weakCompareAndSet must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.WEAK_COMPARE_AND_SET) on this VarHandle.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue) , statically represented using varargs.
        Returns:
        true if successful, otherwisefalse if the witness value was not the same as theexpectedValue or if this operation spuriously failed.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
        See Also:
        setVolatile(Object...),getVolatile(Object...)

      • weakCompareAndSetAcquire

        public final boolean weakCompareAndSetAcquire​(Object... args)
        Possibly atomically sets the value of a variable to thenewValue with the semantics ofset(java.lang.Object...) if the variable's current value, referred to as thewitness value,== theexpectedValue, as accessed with the memory semantics ofgetAcquire(java.lang.Object...).

        This operation may fail spuriously (typically, due to memory contention) even if the witness value does match the expected value.

        The method signature is of the form(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)boolean.

        The symbolic type descriptor at the call site of weakCompareAndSetAcquire must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.WEAK_COMPARE_AND_SET_ACQUIRE) on this VarHandle.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue) , statically represented using varargs.
        Returns:
        true if successful, otherwisefalse if the witness value was not the same as theexpectedValue or if this operation spuriously failed.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
        See Also:
        set(Object...),getAcquire(Object...)

      • weakCompareAndSetRelease

        public final boolean weakCompareAndSetRelease​(Object... args)
        Possibly atomically sets the value of a variable to thenewValue with the semantics ofsetRelease(java.lang.Object...) if the variable's current value, referred to as thewitness value,== theexpectedValue, as accessed with the memory semantics ofget(java.lang.Object...).

        This operation may fail spuriously (typically, due to memory contention) even if the witness value does match the expected value.

        The method signature is of the form(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)boolean.

        The symbolic type descriptor at the call site of weakCompareAndSetRelease must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.WEAK_COMPARE_AND_SET_RELEASE) on this VarHandle.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue) , statically represented using varargs.
        Returns:
        true if successful, otherwisefalse if the witness value was not the same as theexpectedValue or if this operation spuriously failed.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
        See Also:
        setRelease(Object...),get(Object...)

      • getAndSet

        public final Object getAndSet​(Object... args)
        Atomically sets the value of a variable to thenewValue with the memory semantics ofsetVolatile(java.lang.Object...) and returns the variable's previous value, as accessed with the memory semantics ofgetVolatile(java.lang.Object...).

        The method signature is of the form(CT1 ct1, ..., CTn ctn, T newValue)T.

        The symbolic type descriptor at the call site ofgetAndSet must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_SET) on this VarHandle.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T newValue) , statically represented using varargs.
        Returns:
        the signature-polymorphic result that is the previous value of the variable , statically represented usingObject.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
        See Also:
        setVolatile(Object...),getVolatile(Object...)

      • getAndSetAcquire

        public final Object getAndSetAcquire​(Object... args)
        Atomically sets the value of a variable to thenewValue with the memory semantics ofset(java.lang.Object...) and returns the variable's previous value, as accessed with the memory semantics ofgetAcquire(java.lang.Object...).

        The method signature is of the form(CT1 ct1, ..., CTn ctn, T newValue)T.

        The symbolic type descriptor at the call site ofgetAndSetAcquire must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_SET_ACQUIRE) on this VarHandle.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T newValue) , statically represented using varargs.
        Returns:
        the signature-polymorphic result that is the previous value of the variable , statically represented usingObject.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
        See Also:
        setVolatile(Object...),getVolatile(Object...)

      • getAndSetRelease

        public final Object getAndSetRelease​(Object... args)
        Atomically sets the value of a variable to thenewValue with the memory semantics ofsetRelease(java.lang.Object...) and returns the variable's previous value, as accessed with the memory semantics ofget(java.lang.Object...).

        The method signature is of the form(CT1 ct1, ..., CTn ctn, T newValue)T.

        The symbolic type descriptor at the call site ofgetAndSetRelease must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_SET_RELEASE) on this VarHandle.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T newValue) , statically represented using varargs.
        Returns:
        the signature-polymorphic result that is the previous value of the variable , statically represented usingObject.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
        See Also:
        setVolatile(Object...),getVolatile(Object...)

      • getAndAdd

        public final Object getAndAdd​(Object... args)
        Atomically adds thevalue to the current value of a variable with the memory semantics ofsetVolatile(java.lang.Object...), and returns the variable's previous value, as accessed with the memory semantics ofgetVolatile(java.lang.Object...).

        The method signature is of the form(CT1 ct1, ..., CTn ctn, T value)T.

        The symbolic type descriptor at the call site ofgetAndAdd must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_ADD) on this VarHandle.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T value) , statically represented using varargs.
        Returns:
        the signature-polymorphic result that is the previous value of the variable , statically represented usingObject.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
        See Also:
        setVolatile(Object...),getVolatile(Object...)

      • getAndAddAcquire

        public final Object getAndAddAcquire​(Object... args)
        Atomically adds thevalue to the current value of a variable with the memory semantics ofset(java.lang.Object...), and returns the variable's previous value, as accessed with the memory semantics ofgetAcquire(java.lang.Object...).

        The method signature is of the form(CT1 ct1, ..., CTn ctn, T value)T.

        The symbolic type descriptor at the call site ofgetAndAddAcquire must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_ADD_ACQUIRE) on this VarHandle.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T value) , statically represented using varargs.
        Returns:
        the signature-polymorphic result that is the previous value of the variable , statically represented usingObject.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
        See Also:
        setVolatile(Object...),getVolatile(Object...)

      • getAndAddRelease

        public final Object getAndAddRelease​(Object... args)
        Atomically adds thevalue to the current value of a variable with the memory semantics ofsetRelease(java.lang.Object...), and returns the variable's previous value, as accessed with the memory semantics ofget(java.lang.Object...).

        The method signature is of the form(CT1 ct1, ..., CTn ctn, T value)T.

        The symbolic type descriptor at the call site ofgetAndAddRelease must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_ADD_RELEASE) on this VarHandle.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T value) , statically represented using varargs.
        Returns:
        the signature-polymorphic result that is the previous value of the variable , statically represented usingObject.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
        See Also:
        setVolatile(Object...),getVolatile(Object...)

      • getAndBitwiseOr

        public final Object getAndBitwiseOr​(Object... args)
        Atomically sets the value of a variable to the result of bitwise OR between the variable's current value and themask with the memory semantics ofsetVolatile(java.lang.Object...) and returns the variable's previous value, as accessed with the memory semantics ofgetVolatile(java.lang.Object...).

        If the variable type is the non-integralboolean type then a logical OR is performed instead of a bitwise OR.

        The method signature is of the form(CT1 ct1, ..., CTn ctn, T mask)T.

        The symbolic type descriptor at the call site ofgetAndBitwiseOr must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_BITWISE_OR) on this VarHandle.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T mask) , statically represented using varargs.
        Returns:
        the signature-polymorphic result that is the previous value of the variable , statically represented usingObject.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
        See Also:
        setVolatile(Object...),getVolatile(Object...)

      • getAndBitwiseOrAcquire

        public final Object getAndBitwiseOrAcquire​(Object... args)
        Atomically sets the value of a variable to the result of bitwise OR between the variable's current value and themask with the memory semantics ofset(java.lang.Object...) and returns the variable's previous value, as accessed with the memory semantics ofgetAcquire(java.lang.Object...).

        If the variable type is the non-integralboolean type then a logical OR is performed instead of a bitwise OR.

        The method signature is of the form(CT1 ct1, ..., CTn ctn, T mask)T.

        The symbolic type descriptor at the call site ofgetAndBitwiseOrAcquire must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_BITWISE_OR_ACQUIRE) on this VarHandle.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T mask) , statically represented using varargs.
        Returns:
        the signature-polymorphic result that is the previous value of the variable , statically represented usingObject.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
        See Also:
        set(Object...),getAcquire(Object...)

      • getAndBitwiseOrRelease

        public final Object getAndBitwiseOrRelease​(Object... args)
        Atomically sets the value of a variable to the result of bitwise OR between the variable's current value and themask with the memory semantics ofsetRelease(java.lang.Object...) and returns the variable's previous value, as accessed with the memory semantics ofget(java.lang.Object...).

        If the variable type is the non-integralboolean type then a logical OR is performed instead of a bitwise OR.

        The method signature is of the form(CT1 ct1, ..., CTn ctn, T mask)T.

        The symbolic type descriptor at the call site ofgetAndBitwiseOrRelease must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_BITWISE_OR_RELEASE) on this VarHandle.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T mask) , statically represented using varargs.
        Returns:
        the signature-polymorphic result that is the previous value of the variable , statically represented usingObject.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
        See Also:
        setRelease(Object...),get(Object...)

      • getAndBitwiseAnd

        public final Object getAndBitwiseAnd​(Object... args)
        Atomically sets the value of a variable to the result of bitwise AND between the variable's current value and themask with the memory semantics ofsetVolatile(java.lang.Object...) and returns the variable's previous value, as accessed with the memory semantics ofgetVolatile(java.lang.Object...).

        If the variable type is the non-integralboolean type then a logical AND is performed instead of a bitwise AND.

        The method signature is of the form(CT1 ct1, ..., CTn ctn, T mask)T.

        The symbolic type descriptor at the call site ofgetAndBitwiseAnd must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_BITWISE_AND) on this VarHandle.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T mask) , statically represented using varargs.
        Returns:
        the signature-polymorphic result that is the previous value of the variable , statically represented usingObject.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
        See Also:
        setVolatile(Object...),getVolatile(Object...)

      • getAndBitwiseAndAcquire

        public final Object getAndBitwiseAndAcquire​(Object... args)
        Atomically sets the value of a variable to the result of bitwise AND between the variable's current value and themask with the memory semantics ofset(java.lang.Object...) and returns the variable's previous value, as accessed with the memory semantics ofgetAcquire(java.lang.Object...).

        If the variable type is the non-integralboolean type then a logical AND is performed instead of a bitwise AND.

        The method signature is of the form(CT1 ct1, ..., CTn ctn, T mask)T.

        The symbolic type descriptor at the call site ofgetAndBitwiseAndAcquire must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_BITWISE_AND_ACQUIRE) on this VarHandle.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T mask) , statically represented using varargs.
        Returns:
        the signature-polymorphic result that is the previous value of the variable , statically represented usingObject.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
        See Also:
        set(Object...),getAcquire(Object...)

      • getAndBitwiseAndRelease

        public final Object getAndBitwiseAndRelease​(Object... args)
        Atomically sets the value of a variable to the result of bitwise AND between the variable's current value and themask with the memory semantics ofsetRelease(java.lang.Object...) and returns the variable's previous value, as accessed with the memory semantics ofget(java.lang.Object...).

        If the variable type is the non-integralboolean type then a logical AND is performed instead of a bitwise AND.

        The method signature is of the form(CT1 ct1, ..., CTn ctn, T mask)T.

        The symbolic type descriptor at the call site ofgetAndBitwiseAndRelease must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_BITWISE_AND_RELEASE) on this VarHandle.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T mask) , statically represented using varargs.
        Returns:
        the signature-polymorphic result that is the previous value of the variable , statically represented usingObject.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
        See Also:
        setRelease(Object...),get(Object...)

      • getAndBitwiseXor

        public final Object getAndBitwiseXor​(Object... args)
        Atomically sets the value of a variable to the result of bitwise XOR between the variable's current value and themask with the memory semantics ofsetVolatile(java.lang.Object...) and returns the variable's previous value, as accessed with the memory semantics ofgetVolatile(java.lang.Object...).

        If the variable type is the non-integralboolean type then a logical XOR is performed instead of a bitwise XOR.

        The method signature is of the form(CT1 ct1, ..., CTn ctn, T mask)T.

        The symbolic type descriptor at the call site ofgetAndBitwiseXor must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_BITWISE_XOR) on this VarHandle.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T mask) , statically represented using varargs.
        Returns:
        the signature-polymorphic result that is the previous value of the variable , statically represented usingObject.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
        See Also:
        setVolatile(Object...),getVolatile(Object...)

      • getAndBitwiseXorAcquire

        public final Object getAndBitwiseXorAcquire​(Object... args)
        Atomically sets the value of a variable to the result of bitwise XOR between the variable's current value and themask with the memory semantics ofset(java.lang.Object...) and returns the variable's previous value, as accessed with the memory semantics ofgetAcquire(java.lang.Object...).

        If the variable type is the non-integralboolean type then a logical XOR is performed instead of a bitwise XOR.

        The method signature is of the form(CT1 ct1, ..., CTn ctn, T mask)T.

        The symbolic type descriptor at the call site ofgetAndBitwiseXorAcquire must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_BITWISE_XOR_ACQUIRE) on this VarHandle.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T mask) , statically represented using varargs.
        Returns:
        the signature-polymorphic result that is the previous value of the variable , statically represented usingObject.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
        See Also:
        set(Object...),getAcquire(Object...)

      • getAndBitwiseXorRelease

        public final Object getAndBitwiseXorRelease​(Object... args)
        Atomically sets the value of a variable to the result of bitwise XOR between the variable's current value and themask with the memory semantics ofsetRelease(java.lang.Object...) and returns the variable's previous value, as accessed with the memory semantics ofget(java.lang.Object...).

        If the variable type is the non-integralboolean type then a logical XOR is performed instead of a bitwise XOR.

        The method signature is of the form(CT1 ct1, ..., CTn ctn, T mask)T.

        The symbolic type descriptor at the call site ofgetAndBitwiseXorRelease must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_BITWISE_XOR_RELEASE) on this VarHandle.

        Parameters:
        args - the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T mask) , statically represented using varargs.
        Returns:
        the signature-polymorphic result that is the previous value of the variable , statically represented usingObject.
        Throws:
        UnsupportedOperationException - if the access mode is unsupported for this VarHandle.
        WrongMethodTypeException - if the access mode type does not match the caller's symbolic type descriptor.
        ClassCastException - if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
        See Also:
        setRelease(Object...),get(Object...)

      • varType

        public final Class<?> varType()
        Returns the variable type of variables referenced by this VarHandle.
        Returns:
        the variable type of variables referenced by this VarHandle

      • coordinateTypes

        public final List<Class<?>> coordinateTypes()
        Returns the coordinate types for this VarHandle.
        Returns:
        the coordinate types for this VarHandle. The returned list is unmodifiable

      • accessModeType

        public final MethodType accessModeType​(VarHandle.AccessMode accessMode)
        Obtains the access mode type for this VarHandle and a given access mode.

        The access mode type's parameter types will consist of a prefix that is the coordinate types of this VarHandle followed by further types as defined by the access mode method. The access mode type's return type is defined by the return type of the access mode method.

        Parameters:
        accessMode - the access mode, corresponding to the signature-polymorphic method of the same name
        Returns:
        the access mode type for the given access mode

      • isAccessModeSupported

        public final boolean isAccessModeSupported​(VarHandle.AccessMode accessMode)
        Returnstrue if the given access mode is supported, otherwisefalse.

        The return of afalse value for a given access mode indicates that anUnsupportedOperationException is thrown on invocation of the corresponding access mode method.

        Parameters:
        accessMode - the access mode, corresponding to the signature-polymorphic method of the same name
        Returns:
        true if the given access mode is supported, otherwisefalse.

      • toMethodHandle

        public final MethodHandle toMethodHandle​(VarHandle.AccessMode accessMode)
        Obtains a method handle bound to this VarHandle and the given access mode.
        API Note:
        This method, for a VarHandlevh and access mode{access-mode}, returns a method handle that is equivalent to method handlebmh in the following code (though it may be more efficient):
         MethodHandle mh = MethodHandles.varHandleExactInvoker(                       vh.accessModeType(VarHandle.AccessMode.{access-mode})); MethodHandle bmh = mh.bindTo(vh);
        Parameters:
        accessMode - the access mode, corresponding to the signature-polymorphic method of the same name
        Returns:
        a method handle bound to this VarHandle and the given access mode

      • fullFence

        public static void fullFence()
        Ensures that loads and stores before the fence will not be reordered with loads and stores after the fence.
        API Note:
        Ignoring the many semantic differences from C and C++, this method has memory ordering effects compatible withatomic_thread_fence(memory_order_seq_cst)

      • acquireFence

        public static void acquireFence()
        Ensures that loads before the fence will not be reordered with loads and stores after the fence.
        API Note:
        Ignoring the many semantic differences from C and C++, this method has memory ordering effects compatible withatomic_thread_fence(memory_order_acquire)

      • releaseFence

        public static void releaseFence()
        Ensures that loads and stores before the fence will not be reordered with stores after the fence.
        API Note:
        Ignoring the many semantic differences from C and C++, this method has memory ordering effects compatible withatomic_thread_fence(memory_order_release)

      • loadLoadFence

        public static void loadLoadFence()
        Ensures that loads before the fence will not be reordered with loads after the fence.

      • storeStoreFence

        public static void storeStoreFence()
        Ensures that stores before the fence will not be reordered with stores after the fence.