Module java.base

Package java.lang

packagejava.lang
Provides classes that are fundamental to the design of the Java programming language. The most important classes are Object, which is the root of the class hierarchy, and Class, instances of which represent classes at run time.

Frequently it is necessary to represent a value of primitive type as if it were an object. The wrapper classesBoolean,Character,Integer,Long,Float, andDouble serve this purpose. An object of type Double, for example, contains a field whose type is double, representing that value in such a way that a reference to it can be stored in a variable of reference type. These classes also provide a number of methods for converting among primitive values, as well as supporting such standard methods as equals and hashCode. TheVoid class is a non-instantiable class that holds a reference to aClass object representing the type void.

The classMath provides commonly used mathematical functions such as sine, cosine, and square root. The classes String,StringBuffer, andStringBuilder similarly provide commonly used operations on character strings.

ClassesClassLoader,Process, ProcessBuilder,Runtime,SecurityManager, andSystem provide "system operations" that manage the dynamic loading of classes, creation of external processes, host environment inquiries such as the time of day, and enforcement of security policies.

ClassThrowable encompasses objects that may be thrown by thethrow statement. Subclasses ofThrowable represent errors and exceptions.

Character Encodings

The specification of thejava.nio.charset.Charset class describes the naming conventions for character encodings as well as the set of standard encodings that must be supported by every implementation of the Java platform.
Since:
1.0
  • Interface Summary
    Interface
    Description
    An object to whichchar sequences and values can be appended.
    An object that may hold resources (such as file or socket handles) until it is closed.
    ACharSequence is a readable sequence ofchar values.
    A class implements theCloneable interface to indicate to theObject.clone() method that it is legal for that method to make a field-for-field copy of instances of that class.
    This interface imposes a total ordering on the objects of each class that implements it.
    Implementing this interface allows an object to be the target of the enhancedfor statement (sometimes called the "for-each loop" statement).
    ProcessHandle identifies and provides control of native processes.
    Information snapshot about the process.
    AReadable is a source of characters.
    TheRunnable interface should be implemented by any class whose instances are intended to be executed by a thread.
    AStackFrame object represents a method invocation returned byStackWalker.
    System.Logger instances log messages that will be routed to the underlying logging framework theLoggerFinder uses.
    Interface for handlers invoked when aThread abruptly terminates due to an uncaught exception.
  • Class Summary
    Class
    Description
    The Boolean class wraps a value of the primitive typeboolean in an object.
    TheByte class wraps a value of primitive typebyte in an object.
    TheCharacter class wraps a value of the primitive typechar in an object.
    Instances of this class represent particular subsets of the Unicode character set.
    A family of character subsets representing the character blocks in the Unicode specification.
    Instances of the classClass represent classes and interfaces in a running Java application.
    A class loader is an object that is responsible for loading classes.
    Lazily associate a computed value with (potentially) every type.
    Deprecated, for removal: This API element is subject to removal in a future version.
    JIT compilers and their technologies vary too widely to be controlled effectively by a standardized interface.
    TheDouble class wraps a value of the primitive typedouble in an object.
    Enum<E extendsEnum<E>>
    This is the common base class of all Java language enumeration classes.
    Enum.EnumDesc<E extendsEnum<E>>
    Anominal descriptor for anenum constant.
    TheFloat class wraps a value of primitive typefloat in an object.
    This class extendsThreadLocal to provide inheritance of values from parent thread to child thread: when a child thread is created, the child receives initial values for all inheritable thread-local variables for which the parent has values.
    TheInteger class wraps a value of the primitive typeint in an object.
    TheLong class wraps a value of the primitive type long in an object.
    The classMath contains methods for performing basic numeric operations such as the elementary exponential, logarithm, square root, and trigonometric functions.
    Represents a run-time module, eithernamed or unnamed.
    A layer of modules in the Java virtual machine.
    Controls a module layer.
    The abstract classNumber is the superclass of platform classes representing numeric values that are convertible to the primitive typesbyte,double,float, int,long, andshort.
    ClassObject is the root of the class hierarchy.
    Represents metadata about a run-time package associated with a class loader.
    Process provides control of native processes started by ProcessBuilder.start and Runtime.exec.
    This class is used to create operating system processes.
    Represents a source of subprocess input or a destination of subprocess output.
    This is the common base class of all Java language record classes.
    Every Java application has a single instance of classRuntime that allows the application to interface with the environment in which the application is running.
    A representation of a version string for an implementation of the Java SE Platform.
    This class is for runtime permissions.
    The security manager is a class that allows applications to implement a security policy.
    TheShort class wraps a value of primitive type short in an object.
    An element in a stack trace, as returned byThrowable.getStackTrace().
    A stack walker.
    The classStrictMath contains methods for performing basic numeric operations such as the elementary exponential, logarithm, square root, and trigonometric functions.
    TheString class represents character strings.
    A thread-safe, mutable sequence of characters.
    A mutable sequence of characters.
    TheSystem class contains several useful class fields and methods.
    TheLoggerFinder service is responsible for creating, managing, and configuring loggers to the underlying framework it uses.
    Athread is a thread of execution in a program.
    A thread group represents a set of threads.
    This class provides thread-local variables.
    TheThrowable class is the superclass of all errors and exceptions in the Java language.
    TheVoid class is an uninstantiable placeholder class to hold a reference to theClass object representing the Java keyword void.
  • Enum Class Summary
    Enum Class
    Description
    A family of character subsets representing the character scripts defined in theUnicode Standard Annex #24: Script Names.
    Stack walker option to configure thestack frame information obtained by aStackWalker.
    Systemloggers levels.
    A thread state.
  • Exception Summary
    Exception
    Description
    Thrown when an exceptional arithmetic condition has occurred.
    Thrown to indicate that an array has been accessed with an illegal index.
    Thrown to indicate that an attempt has been made to store the wrong type of object into an array of objects.
    Thrown to indicate that the code has attempted to cast an object to a subclass of which it is not an instance.
    Thrown when an application tries to load in a class through its string name using: TheforName method in classClass.
    Thrown to indicate that theclone method in classObject has been called to clone an object, but that the object's class does not implement theCloneable interface.
    Thrown when an application tries to access an enum constant by name and the enum type contains no constant with the specified name.
    The classException and its subclasses are a form ofThrowable that indicates conditions that a reasonable application might want to catch.
    An IllegalAccessException is thrown when an application tries to reflectively create an instance (other than an array), set or get a field, or invoke a method, but the currently executing method does not have access to the definition of the specified class, field, method or constructor.
    Thrown to indicate that a method has been passed an illegal or inappropriate argument.
    Thrown to indicate that a method has been called by an inappropriate caller.
    Thrown to indicate that a thread has attempted to wait on an object's monitor or to notify other threads waiting on an object's monitor without owning the specified monitor.
    Signals that a method has been invoked at an illegal or inappropriate time.
    Thrown to indicate that a thread is not in an appropriate state for the requested operation.
    Thrown to indicate that an index of some sort (such as to an array, to a string, or to a vector) is out of range.
    Thrown when an application tries to create an instance of a class using thenewInstance method in classClass, but the specified class object cannot be instantiated.
    Thrown when a thread is waiting, sleeping, or otherwise occupied, and the thread is interrupted, either before or during the activity.
    Thrown when creating amodule layer fails.
    Thrown if an application tries to create an array with negative size.
    Signals that the class doesn't have a field of a specified name.
    Thrown when a particular method cannot be found.
    Thrown when an application attempts to usenull in a case where an object is required.
    Thrown to indicate that the application has attempted to convert a string to one of the numeric types, but that the string does not have the appropriate format.
    Common superclass of exceptions thrown by reflective operations in core reflection.
    RuntimeException is the superclass of those exceptions that can be thrown during the normal operation of the Java Virtual Machine.
    Thrown by the security manager to indicate a security violation.
    Thrown byString methods to indicate that an index is either negative or greater than the size of the string.
    Thrown when an application tries to access a type using a string representing the type's name, but no definition for the type with the specified name can be found.
    Thrown to indicate that the requested operation is not supported.
  • Error Summary
    Error
    Description
    Thrown when an application tries to call an abstract method.
    Thrown to indicate that an assertion has failed.
    Thrown to indicate that aninvokedynamic instruction or a dynamic constant failed to resolve its bootstrap method and arguments, or forinvokedynamic instruction the bootstrap method has failed to provide acall site with atarget of the correctmethod type, or for a dynamic constant the bootstrap method has failed to provide a constant value of the required type.
    Thrown when the Java Virtual Machine detects a circularity in the superclass hierarchy of a class being loaded.
    Thrown when the Java Virtual Machine attempts to read a class file and determines that the file is malformed or otherwise cannot be interpreted as a class file.
    AnError is a subclass ofThrowable that indicates serious problems that a reasonable application should not try to catch.
    Signals that an unexpected exception has occurred in a static initializer.
    Thrown if an application attempts to access or modify a field, or to call a method that it does not have access to.
    Thrown when an incompatible class change has occurred to some class definition.
    Thrown when an application tries to use the Javanew construct to instantiate an abstract class or an interface.
    Thrown to indicate some unexpected internal error has occurred in the Java Virtual Machine.
    Subclasses ofLinkageError indicate that a class has some dependency on another class; however, the latter class has incompatibly changed after the compilation of the former class.
    Thrown if the Java Virtual Machine or aClassLoader instance tries to load in the definition of a class (as part of a normal method call or as part of creating a new instance using thenew expression) and no definition of the class could be found.
    Thrown if an application tries to access or modify a specified field of an object, and that object no longer has that field.
    Thrown if an application tries to call a specified method of a class (either static or instance), and that class no longer has a definition of that method.
    Thrown when the Java Virtual Machine cannot allocate an object because it is out of memory, and no more memory could be made available by the garbage collector.
    Thrown when a stack overflow occurs because an application recurses too deeply.
    An instance ofThreadDeath is thrown in the victim thread when the (deprecated)Thread.stop() method is invoked.
    Thrown when an unknown but serious exception has occurred in the Java Virtual Machine.
    Thrown if the Java Virtual Machine cannot find an appropriate native-language definition of a method declarednative.
    Thrown when the Java Virtual Machine attempts to read a class file and determines that the major and minor version numbers in the file are not supported.
    Thrown when the "verifier" detects that a class file, though well formed, contains some sort of internal inconsistency or security problem.
    Thrown to indicate that the Java Virtual Machine is broken or has run out of resources necessary for it to continue operating.
  • Annotation Interfaces Summary
    Annotation Interface
    Description
    A program element annotated@Deprecated is one that programmers are discouraged from using.
    An informative annotation type used to indicate that an interface type declaration is intended to be afunctional interface as defined by the Java Language Specification.
    Indicates that a method declaration is intended to override a method declaration in a supertype.
    A programmer assertion that the body of the annotated method or constructor does not perform potentially unsafe operations on its varargs parameter.
    Indicates that the named compiler warnings should be suppressed in the annotated element (and in all program elements contained in the annotated element).