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Package java.lang
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.
Since:
1.0
Frequently it is necessary to represent a value of primitive type as if it were an object.The wrapper classes Boolean, Byte, Character, Short, 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. As discussed in The Java Language Specification, the wrapper classes are involved in boxing (JLS 5.1.7) and unboxing (JLS 5.1.8) conversions. These classes provide a number of methods for converting among primitive values, as well as methods supporting such standard functionality 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, and System provide "system operations" that manage the dynamic loading of classes, creation of external processes, and host environment inquiries such as the time of day.
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.-
All Classes and InterfacesInterfacesClassesEnum ClassesException ClassesAnnotation InterfacesClassDescriptionThrown when an application tries to call an abstract method.An object to which char 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 the wrong 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.The Boolean class is the wrapper class for values of the primitive type boolean.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.The Byte class is the wrapper class for values of the primitive type byte.The Character class is the wrapper class for values of the primitive type char.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.A family of character subsets representing the character scripts defined in the Unicode Standard Annex #24: Script Names.A CharSequence is a readable sequence of char values.Class<T>Instances of the class Class represent classes and interfaces in a running Java application.Thrown to indicate that the code has attempted to cast an object to a subclass of which it is not an instance.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.A class loader is an object that is responsible for loading classes.Thrown when an application tries to load in a class through its string name using: The forName method in class Class.ClassValue<T>Lazily associate a computed value with any Class object.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.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.Comparable<T>This interface imposes a total ordering on the objects of each class that implements it.A program element annotated @Deprecated is one that programmers are discouraged from using.The Double class is the wrapper class for values of the primitive type double.This is the common base class of all Java language enumeration classes.Enum.EnumDesc<E extends Enum<E>>A nominal descriptor for an enum constant.Thrown when an application tries to access an enum constant by name and the enum type contains no constant with the specified name.An Error is a subclass of Throwable that indicates serious problems that a reasonable application should not try to catch.The class Exception and its subclasses are a form of Throwable that indicates conditions that a reasonable application might want to catch.Signals that an unexpected exception has occurred in a static initializer.The Float class is the wrapper class for values of the primitive type float.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.Thrown if an application attempts to access or modify a field, or to call a method that it does not have access to.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 when an incompatible class change has occurred to some class definition.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.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.Thrown when an application tries to use the Java new construct to instantiate an abstract class or an interface.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.The Integer class is the wrapper class for values of the primitive type int.Thrown to indicate some unexpected internal error has occurred in the Java Virtual Machine.Thrown when a thread executing a blocking method is interrupted.A collection of static methods that provide convenient access to System.in and System.out for line-oriented input and output.Iterable<T>Implementing this interface allows an object to be the target of the enhanced for statement (sometimes called the "for-each loop" statement).Thrown when creating a module layer fails.Preview.A lazy constant is a holder of contents that can be set at most once.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.The Long class is the wrapper class for values of the primitive type long.Thrown to indicate an unexpected failure in pattern matching.The class Math contains methods for performing basic numeric operations such as the elementary exponential, logarithm, square root, and trigonometric functions.Represents a run-time module, either named 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 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.Thrown if an application tries to access or modify a specified field 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 a class (either static or instance), and that class no longer has a definition of that method.Thrown when a particular method cannot be found.Thrown when an application attempts to use null in a case where an object is required.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.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.Class Object is the root of the class hierarchy.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.Indicates that a method declaration is intended to override a method declaration in a supertype.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.The type of a ProcessBuilder.Redirect.ProcessHandle identifies and provides control of native processes.Information snapshot about the process.A Readable 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 in core reflection.Represents an operation that does not return a result.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.A representation of a version string for an implementation of the Java SE Platform.RuntimeException is the superclass of those exceptions that can be thrown during the normal operation of the Java 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 resources as the Security Manager is no longer supported.A programmer assertion that the body of the annotated method or constructor does not perform potentially unsafe operations on its varargs parameter.ScopedValue<T>A value that may be safely and efficiently shared to methods without using method parameters.ScopedValue.CallableOp<T, X extends Throwable>An operation that returns a result and may throw an exception.A mapping of scoped values, as keys, 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.The Short class is the wrapper class for values of the primitive type short.Thrown when a stack overflow occurs because an application recurses too deeply.An element in a stack trace, as returned by Throwable.getStackTrace().A stack walker.Stack walker option to configure the stack frame information obtained by a StackWalker.A StackFrame object represents a method invocation returned by StackWalker.The class StrictMath contains methods for performing basic numeric operations such as the elementary exponential, logarithm, square root, and trigonometric functions.The String class represents character strings.A thread-safe, mutable sequence of characters.A mutable sequence of characters.Thrown by String methods to indicate that an index is either negative or greater than the size of the string.Indicates the warnings to be suppressed at compile time in the annotated element, and in all elements contained in the annotated element.The System class contains several useful class fields and methods.System.Logger instances log messages that will be routed to the underlying logging framework the LoggerFinder uses.System loggers levels.The LoggerFinder service is responsible for creating, managing, and configuring loggers to the underlying framework it uses.A thread is a thread of execution in a program.A builder for Thread and ThreadFactory objects.A builder for creating a platform Thread or ThreadFactory that creates platform threads.A builder for creating a virtual Thread or ThreadFactory that creates virtual threads.A thread state.Interface for handlers invoked when a Thread abruptly terminates due to an uncaught exception.Deprecated, for removal: This API element is subject to removal in a future version.Thread originally specified a "stop" method to stop a victim thread by causing the victim thread to throw a ThreadDeath.A thread group represents a set of threads.ThreadLocal<T>This class provides thread-local variables.The Throwable class is the superclass of all errors and exceptions in the Java language.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 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 declared native.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 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 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.The Void class is an uninstantiable placeholder class to hold a reference to the Class object representing the Java keyword void.Thrown to indicate that a method has been called on the wrong thread.
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For further API reference and developer documentation see the Java SE Documentation, which contains more detailed, developer-targeted descriptions with conceptual overviews, definitions of terms, workarounds, and working code examples. Other versions.
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