Package java.lang

packagejava.lang
Provides classes that are fundamental to the design of the Javaprogramming language. The most important classes areObject, which is the root of the class hierarchy, andClass, instances of which represent classes at run time.

Frequently it is necessary to represent avalue of primitive type as if it were an object.Thewrapper classesBoolean,Byte,Character,Short,Integer,Long,Float, andDouble serve this purpose. An object of typeDouble, for example, contains a field whose type isdouble, representing that value in such a way that a reference toit can be stored in a variable of reference type. As discussed inThe Java Language Specification, the wrapper classesare involved in boxing (JLS5.1.7) and unboxing (JLS5.1.8) conversions. These classes provide a number of methods forconverting among primitive values, as well as methods supportingsuch standard functionality asequals andhashCode.TheVoid class is a non-instantiable class that holds areference to aClass object representing the typevoid.

The classMath provides commonly used mathematicalfunctions such assine,cosine, andsquareroot. The classesString,StringBuffer, andStringBuilder similarly provide commonly used operations oncharacter strings.

ClassesClassLoader,Process,ProcessBuilder,Runtime, andSystem provide "system operations" thatmanage the dynamic loading of classes, creation of external processes,and host environment inquiries such as the time of day.

ClassThrowable encompasses objects that may be thrownby thethrow statement. Subclasses ofThrowablerepresent errors and exceptions.

Character Encodings

The specification of thejava.nio.charset.Charset class describes the naming conventionsfor character encodings as well as the set of standard encodingsthat must be supported by every implementation of the Javaplatform.
Since:
1.0
  • Related Packages
    Module
    Package
    Description
    Provides library support for the Java programming languageannotation facility.
    Provides classfile parsing, generation, and transformation library.
    Classes and interfaces to representnominal descriptors for run-timeentities such as classes or method handles, and classfile entities such asconstant pool entries orinvokedynamic call sites.
    Provides low-level access to memory and functions outside the Java runtime.
    Provides services that allow Java programming language agents to instrumentprograms running on the Java Virtual Machine (JVM).
    Thejava.lang.invoke package provides low-level primitives for interactingwith the Java Virtual Machine.
    Provides the management interfaces for monitoring and management of theJava virtual machine and other components in the Java runtime.
    Classes to support module descriptors and creating configurations of modulesby means of resolution and service binding.
    Provides reference-object classes, which support a limited degreeof interaction with the garbage collector.
    Provides classes and interfaces for obtaining reflective information aboutclasses and objects.
    Thejava.lang.runtime package provides low-level runtime supportfor the Java language.
  • Class
    Description
    Thrown when an application tries to call an abstract method.
    An object to whichchar sequences and values can be appended.
    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 thewrong type of object into an array of objects.
    Thrown to indicate that an assertion has failed.
    An object that may hold resources (such as file or socket handles)until it is closed.
    TheBoolean class is thewrapper class for values of the primitivetypeboolean.
    Thrown to indicate that aninvokedynamic instruction or a dynamicconstant failed to resolve its bootstrap method and arguments,or forinvokedynamic instruction the bootstrap method has failed toprovide acall site with atargetof the correctmethod type,or for a dynamic constant the bootstrap method has failed to provide aconstant value of the required type.
    TheByte class is thewrapper class for values of the primitivetypebyte.
    TheCharacter class is thewrapper class for values of the primitivetypechar.
    Instances of this class represent particular subsets of the Unicodecharacter set.
    A family of character subsets representing the character blocks in theUnicode specification.
    A family of character subsets representing the character scriptsdefined in theUnicode Standard Annex #24: Script Names.
    ACharSequence is a readable sequence ofchar values.
    Instances of the classClass represent classes andinterfaces in a running Java application.
    Thrown to indicate that the code has attempted to cast an objectto a subclass of which it is not an instance.
    Thrown when the Java Virtual Machine detects a circularity in thesuperclass hierarchy of a class being loaded.
    Thrown when the Java Virtual Machine attempts to read a classfile and determines that the file is malformed or otherwise cannotbe interpreted as a class file.
    A class loader is an object that is responsible for loading classes.
    Thrown when an application tries to load in a class through itsstring name using:TheforName method in classClass.
    Lazily associate a computed value with anyClass object.
    A class implements theCloneable interface toindicate to theObject.clone() method that itis legal for that method to make afield-for-field copy of instances of that class.
    Thrown to indicate that theclone method in classObject has been called to clone an object, but thatthe object's class does not implement theCloneableinterface.
    This interface imposes a total ordering on the objects of each class thatimplements it.
    A program element annotated@Deprecated is one that programmersare discouraged from using.
    TheDouble class is thewrapper class for values of the primitive typedouble.
    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.
    Thrown when an application tries to access an enum constant by nameand the enum type contains no constant with the specified name.
    AnError is a subclass ofThrowablethat indicates serious problems that a reasonable applicationshould not try to catch.
    The classException and its subclasses are a form ofThrowable that indicates conditions that a reasonableapplication might want to catch.
    Signals that an unexpected exception has occurred in a static initializer.
    TheFloat class is thewrapper class for values of the primitivetypefloat.
    An informative annotation type used to indicate that an interfacetype declaration is intended to be afunctional interface asdefined by the Java Language Specification.
    Thrown if an application attempts to access or modify a field, orto call a method that it does not have access to.
    An IllegalAccessException is thrown when an application triesto reflectively create an instance (other than an array),set or get a field, or invoke a method, but the currentlyexecuting method does not have access to the definition ofthe specified class, field, method or constructor.
    Thrown to indicate that a method has been passed an illegal orinappropriate 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 anobject's monitor or to notify other threads waiting on an object'smonitor without owning the specified monitor.
    Signals that a method has been invoked at an illegal orinappropriate time.
    Thrown to indicate that a thread is not in an appropriate statefor the requested operation.
    Thrown when an incompatible class change has occurred to some classdefinition.
    Thrown to indicate that an index of some sort (such as to an array, to astring, or to a vector) is out of range.
    This class extendsThreadLocal to provide inheritance of valuesfrom parent thread to child thread: when a child thread is created, thechild receives initial values for all inheritable thread-local variablesfor which the parent has values.
    Thrown when an application tries to use the Javanewconstruct to instantiate an abstract class or an interface.
    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.
    TheInteger class is thewrapper class for values of the primitivetypeint.
    Thrown to indicate some unexpected internal error has occurred inthe Java Virtual Machine.
    Thrown when a thread is waiting, sleeping, or otherwise occupied,and the thread is interrupted, either before or during the activity.
    A collection of static methods that provide convenient access toSystem.inandSystem.out for line-oriented input and output.
    Implementing this interface allows an object to be the target of the enhancedfor statement (sometimes called the "for-each loop" statement).
    Thrown when creating amodule layer fails.
    Subclasses ofLinkageError indicate that a class hassome dependency on another class; however, the latter class hasincompatibly changed after the compilation of the former class.
    TheLong class is thewrapper class for values of the primitivetypelong.
    Thrown to indicate an unexpected failure in pattern matching.
    The classMath contains methods for performing basicnumeric 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.
    Thrown if an application tries to create an array with negative size.
    Thrown if the Java Virtual Machine or aClassLoader instancetries to load in the definition of a class (as part of a normal method callor 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 specifiedfield of an object, and that object no longer has that field.
    Signals that the class doesn't have a field of a specified name.
    Thrown if an application tries to call a specified method of aclass (either static or instance), and that class no longer has adefinition of that method.
    Thrown when a particular method cannot be found.
    Thrown when an application attempts to usenull in acase where an object is required.
    The abstract classNumber is the superclass of platformclasses representing numeric values that are convertible to theprimitive typesbyte,double,float,int,long, andshort.
    Thrown to indicate that the application has attempted to converta string to one of the numeric types, but that the string does nothave the appropriate format.
    ClassObject is the root of the class hierarchy.
    Thrown when the Java Virtual Machine cannot allocate an objectbecause it is out of memory, and no more memory could be madeavailable by the garbage collector.
    Indicates that a method declaration is intended to override amethod declaration in a supertype.
    Represents metadata about a run-time package associated with a class loader.
    Process provides control of native processes started byProcessBuilder.start andRuntime.exec.
    This class is used to create operating system processes.
    Represents a source of subprocess input or a destination ofsubprocess output.
    ProcessHandle identifies and provides control of native processes.
    Information snapshot about the process.
    AReadable is a source of characters.
    This is the common base class of all Java language record classes.
    Common superclass of exceptions thrown by reflective operations incore reflection.
    Represents an operation that does not return a result.
    Every Java application has a single instance of classRuntime that allows the application to interface withthe environment in which the application is running.
    A representation of a version string for an implementation of theJava SE Platform.
    RuntimeException is the superclass of thoseexceptions that can be thrown during the normal operation of theJava Virtual Machine.
    Deprecated, for removal: This API element is subject to removal in a future version.
    This permission cannot be used for controlling access to resourcesas the Security Manager is no longer supported.
    A programmer assertion that the body of the annotated method orconstructor does not perform potentially unsafe operations on itsvarargs parameter.
    A value that may be safely and efficiently shared to methods without using methodparameters.
    An operation that returns a result and may throw an exception.
    A mapping of scoped values, askeys, to values.
    Thrown to indicate a security violation.
    Deprecated, for removal: This API element is subject to removal in a future version.
    There is no replacement for this class.
    TheShort class is thewrapper class for values of the primitivetypeshort.
    Preview.
    A stable value is a holder of contents that can be set at most once.
    Thrown when a stack overflow occurs because an applicationrecurses too deeply.
    An element in a stack trace, as returned byThrowable.getStackTrace().
    A stack walker.
    Stack walker option to configure thestack frameinformation obtained by aStackWalker.
    AStackFrame object represents a method invocation returned byStackWalker.
    The classStrictMath contains methods for performing basicnumeric 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.
    Thrown byString methods to indicate that an index is either negativeor greater than the size of the string.
    Indicates the warnings to be suppressed at compile time in theannotated element, and in all elements contained in the annotatedelement.
    TheSystem class contains several useful class fieldsand methods.
    System.Logger instances log messages that will berouted to the underlying logging framework theLoggerFinder uses.
    Systemloggers levels.
    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 builder forThread andThreadFactory objects.
    A builder for creating a platformThread orThreadFactorythat creates platform threads.
    A builder for creating a virtualThread orThreadFactorythat creates virtual threads.
    A thread state.
    Interface for handlers invoked when aThread abruptlyterminates due to an uncaught exception.
    Deprecated, for removal: This API element is subject to removal in a future version.
    Thread.stop() was originally specified to "stop" a victim thread by causing the victim thread to throw aThreadDeath.
    A thread group represents a set of threads.
    This class provides thread-local variables.
    TheThrowable class is the superclass of all errors andexceptions in the Java language.
    Thrown when an application tries to access a type using a stringrepresenting the type's name, but no definition for the type withthe specified name can be found.
    Thrown when an unknown but serious exception has occurred in theJava Virtual Machine.
    Thrown if the Java Virtual Machine cannot find an appropriatenative-language definition of a method declarednative.
    Thrown when the Java Virtual Machine attempts to read a classfile and determines that the major and minor version numbersin the file are not supported.
    Thrown to indicate that the requested operation is not supported.
    Thrown when the "verifier" detects that a class file,though well formed, contains some sort of internal inconsistencyor security problem.
    Thrown to indicate that the Java Virtual Machine is broken or hasrun out of resources necessary for it to continue operating.
    TheVoid class is an uninstantiable placeholder class to hold areference to theClass object representing the Java keywordvoid.
    Thrown to indicate that a method has been called on the wrong thread.