Module java.base

Package java.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 classes Boolean, Character, Integer, Long, Float, and Double 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. The Void class is a non-instantiable class that holds a reference to a Class object representing the type void.

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

Classes ClassLoader, Process, ProcessBuilder, Runtime, SecurityManager, and System 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.

Class Throwable encompasses objects that may be thrown by the throw statement. Subclasses of Throwable represent errors and exceptions.

Character Encodings

The specification of the java.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
    Appendable
    An object to which char sequences and values can be appended.
    AutoCloseable
    An object that may hold resources (such as file or socket handles) until it is closed.
    CharSequence
    A CharSequence is a readable sequence of char values.
    Cloneable
    A class implements the Cloneable interface to indicate to the Object.clone() method that it is legal for that method to make a field-for-field copy of instances of that class.
    Comparable<T>
    This interface imposes a total ordering on the objects of each class that implements it.
    Iterable<T>
    Implementing this interface allows an object to be the target of the enhanced for statement (sometimes called the "for-each loop" statement).
    ProcessHandle
    ProcessHandle identifies and provides control of native processes.
    ProcessHandle.Info
    Information snapshot about the process.
    Readable
    A Readable is a source of characters.
    Runnable
    The Runnable interface should be implemented by any class whose instances are intended to be executed by a thread.
    StackWalker.StackFrame
    A StackFrame object represents a method invocation returned by StackWalker.
    System.Logger
    System.Logger instances log messages that will be routed to the underlying logging framework the LoggerFinder uses.
    Thread.Builder
    A mutable builder for a Thread or ThreadFactory.
    Thread.UncaughtExceptionHandler
    Interface for handlers invoked when a Thread abruptly terminates due to an uncaught exception.
    Thread.VirtualThreadTask
    The task submitted to a custom scheduler.
  • Class Summary
    Class Description
    Boolean
    The Boolean class wraps a value of the primitive type boolean in an object.
    Byte
    The Byte class wraps a value of primitive type byte in an object.
    Character
    The Character class wraps a value of the primitive type char in an object.
    Character.Subset
    Instances of this class represent particular subsets of the Unicode character set.
    Character.UnicodeBlock
    A family of character subsets representing the character blocks in the Unicode specification.
    Class<T>
    Instances of the class Class represent classes and interfaces in a running Java application.
    ClassLoader
    A class loader is an object that is responsible for loading classes.
    ClassValue<T>
    Lazily associate a computed value with (potentially) every type.
    Compiler 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.
    Continuation
    TBD
    ContinuationScope
    A Continuation scope.
    Double
    The Double class wraps a value of the primitive type double in an object.
    Enum<E extends Enum<E>>
    This is the common base class of all Java language enumeration types.
    Enum.EnumDesc<E extends Enum<E>>
    A nominal descriptor for an enum constant.
    Float
    The Float class wraps a value of primitive type float in an object.
    InheritableThreadLocal<T>
    This class extends ThreadLocal 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.
    Integer
    The Integer class wraps a value of the primitive type int in an object.
    Lifetime
    TBD A Lifetime is a Thing.
    Long
    The Long class wraps a value of the primitive type long in an object.
    Math
    The class Math contains methods for performing basic numeric operations such as the elementary exponential, logarithm, square root, and trigonometric functions.
    Module
    Represents a run-time module, either named or unnamed.
    ModuleLayer
    A layer of modules in the Java virtual machine.
    ModuleLayer.Controller
    Controls a module layer.
    Number
    The abstract class Number is the superclass of platform classes representing numeric values that are convertible to the primitive types byte, double, float, int, long, and short.
    Object
    Class Object is the root of the class hierarchy.
    Package
    Represents metadata about a run-time package associated with a class loader.
    Process
    Process provides control of native processes started by ProcessBuilder.start and Runtime.exec.
    ProcessBuilder
    This class is used to create operating system processes.
    ProcessBuilder.Redirect
    Represents a source of subprocess input or a destination of subprocess output.
    Record
    Associated with records, a preview feature of the Java language.

    This is the common base class of all Java language record classes.
    Runtime
    Every Java application has a single instance of class Runtime that allows the application to interface with the environment in which the application is running.
    Runtime.Version
    A representation of a version string for an implementation of the Java SE Platform.
    RuntimePermission
    This class is for runtime permissions.
    Scoped<T>
    TBD
    ScopedBinding
    TBD
    SecurityManager
    The security manager is a class that allows applications to implement a security policy.
    Short
    The Short class wraps a value of primitive type short in an object.
    StackTraceElement
    An element in a stack trace, as returned by Throwable.getStackTrace().
    StackWalker
    A stack walker.
    StrictMath
    The class StrictMath contains methods for performing basic numeric operations such as the elementary exponential, logarithm, square root, and trigonometric functions.
    String
    The String class represents character strings.
    StringBuffer
    A thread-safe, mutable sequence of characters.
    StringBuilder
    A mutable sequence of characters.
    System
    The System class contains several useful class fields and methods.
    System.LoggerFinder
    The LoggerFinder service is responsible for creating, managing, and configuring loggers to the underlying framework it uses.
    TemporalResource
    TBD A TemporalResource is a Thing.
    Thread
    A thread is a thread of execution in a program.
    ThreadGroup
    A thread group represents a set of threads.
    ThreadLocal<T>
    This class provides thread-local variables.
    Throwable
    The Throwable class is the superclass of all errors and exceptions in the Java language.
    Void
    The Void class is an uninstantiable placeholder class to hold a reference to the Class object representing the Java keyword void.
  • Enum Summary
    Enum Description
    Character.UnicodeScript
    A family of character subsets representing the character scripts defined in the Unicode Standard Annex #24: Script Names.
    Continuation.Pinned
    Reason for pinning
    Continuation.PreemptStatus
    Preemption attempt result
    ProcessBuilder.Redirect.Type
    StackWalker.Option
    Stack walker option to configure the stack frame information obtained by a StackWalker.
    System.Logger.Level
    System loggers levels.
    Thread.State
    A thread state.
  • Exception Summary
    Exception Description
    ArithmeticException
    Thrown when an exceptional arithmetic condition has occurred.
    ArrayIndexOutOfBoundsException
    Thrown to indicate that an array has been accessed with an illegal index.
    ArrayStoreException
    Thrown to indicate that an attempt has been made to store the wrong type of object into an array of objects.
    ClassCastException
    Thrown to indicate that the code has attempted to cast an object to a subclass of which it is not an instance.
    ClassNotFoundException
    Thrown when an application tries to load in a class through its string name using: The forName method in class Class.
    CloneNotSupportedException
    Thrown to indicate that the clone method in class Object has been called to clone an object, but that the object's class does not implement the Cloneable interface.
    EnumConstantNotPresentException
    Thrown when an application tries to access an enum constant by name and the enum type contains no constant with the specified name.
    Exception
    The class Exception and its subclasses are a form of Throwable that indicates conditions that a reasonable application might want to catch.
    IllegalAccessException
    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.
    IllegalArgumentException
    Thrown to indicate that a method has been passed an illegal or inappropriate argument.
    IllegalCallerException
    Thrown to indicate that a method has been called by an inappropriate caller.
    IllegalMonitorStateException
    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.
    IllegalStateException
    Signals that a method has been invoked at an illegal or inappropriate time.
    IllegalThreadStateException
    Thrown to indicate that a thread is not in an appropriate state for the requested operation.
    IndexOutOfBoundsException
    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.
    InstantiationException
    Thrown when an application tries to create an instance of a class using the newInstance method in class Class, but the specified class object cannot be instantiated.
    InterruptedException
    Thrown when a thread is waiting, sleeping, or otherwise occupied, and the thread is interrupted, either before or during the activity.
    LayerInstantiationException
    Thrown when creating a module layer fails.
    NegativeArraySizeException
    Thrown if an application tries to create an array with negative size.
    NoSuchFieldException
    Signals that the class doesn't have a field of a specified name.
    NoSuchMethodException
    Thrown when a particular method cannot be found.
    NullPointerException
    Thrown when an application attempts to use null in a case where an object is required.
    NumberFormatException
    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.
    ReflectiveOperationException
    Common superclass of exceptions thrown by reflective operations in core reflection.
    RuntimeException
    RuntimeException is the superclass of those exceptions that can be thrown during the normal operation of the Java Virtual Machine.
    ScopedAlreadyBoundException
    TBD
    SecurityException
    Thrown by the security manager to indicate a security violation.
    StringIndexOutOfBoundsException
    Thrown by String methods to indicate that an index is either negative or greater than the size of the string.
    TypeNotPresentException
    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.
    UnboundScopedException
    TBD
    UnsupportedOperationException
    Thrown to indicate that the requested operation is not supported.
  • Error Summary
    Error Description
    AbstractMethodError
    Thrown when an application tries to call an abstract method.
    AssertionError
    Thrown to indicate that an assertion has failed.
    BootstrapMethodError
    Thrown to indicate that an invokedynamic instruction or a dynamic constant failed to resolve its bootstrap method and arguments, or for invokedynamic instruction the bootstrap method has failed to provide a call site with a target of the correct method type, or for a dynamic constant the bootstrap method has failed to provide a constant value of the required type.
    ClassCircularityError
    Thrown when the Java Virtual Machine detects a circularity in the superclass hierarchy of a class being loaded.
    ClassFormatError
    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.
    Error
    An Error is a subclass of Throwable that indicates serious problems that a reasonable application should not try to catch.
    ExceptionInInitializerError
    Signals that an unexpected exception has occurred in a static initializer.
    IllegalAccessError
    Thrown if an application attempts to access or modify a field, or to call a method that it does not have access to.
    IncompatibleClassChangeError
    Thrown when an incompatible class change has occurred to some class definition.
    InstantiationError
    Thrown when an application tries to use the Java new construct to instantiate an abstract class or an interface.
    InternalError
    Thrown to indicate some unexpected internal error has occurred in the Java Virtual Machine.
    LifetimeError
    TBD
    LinkageError
    Subclasses of LinkageError indicate that a class has some dependency on another class; however, the latter class has incompatibly changed after the compilation of the former class.
    NoClassDefFoundError
    Thrown if the Java Virtual Machine or a ClassLoader 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 the new expression) and no definition of the class could be found.
    NoSuchFieldError
    Thrown if an application tries to access or modify a specified field of an object, and that object no longer has that field.
    NoSuchMethodError
    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.
    OutOfMemoryError
    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.
    StackOverflowError
    Thrown when a stack overflow occurs because an application recurses too deeply.
    ThreadDeath
    An instance of ThreadDeath is thrown in the victim thread when the (deprecated) Thread.stop() method is invoked.
    UnknownError
    Thrown when an unknown but serious exception has occurred in the Java Virtual Machine.
    UnsatisfiedLinkError
    Thrown if the Java Virtual Machine cannot find an appropriate native-language definition of a method declared native.
    UnsupportedClassVersionError
    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.
    VerifyError
    Thrown when the "verifier" detects that a class file, though well formed, contains some sort of internal inconsistency or security problem.
    VirtualMachineError
    Thrown to indicate that the Java Virtual Machine is broken or has run out of resources necessary for it to continue operating.
  • Annotation Types Summary
    Annotation Type Description
    Deprecated
    A program element annotated @Deprecated is one that programmers are discouraged from using.
    FunctionalInterface
    An informative annotation type used to indicate that an interface type declaration is intended to be a functional interface as defined by the Java Language Specification.
    Override
    Indicates that a method declaration is intended to override a method declaration in a supertype.
    SafeVarargs
    A programmer assertion that the body of the annotated method or constructor does not perform potentially unsafe operations on its varargs parameter.
    SuppressWarnings
    Indicates that the named compiler warnings should be suppressed in the annotated element (and in all program elements contained in the annotated element).