Provides classes that are fundamental to the design of the Java programming language. The most important classes are
, which is the root of the class hierarchy, and
, 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
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.
Math provides commonly used mathematical functions such as sine, cosine, and square root. The classes
StringBuilder similarly provide commonly used operations on character strings.
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.
Throwable encompasses objects that may be thrown by the
throw statement. Subclasses of
Throwable represent errors and exceptions.
The specification of the
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.
|| A program element annotated @Deprecated is one that programmers are discouraged from using, typically because it is dangerous, or because a better alternative exists.
|| 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.
|| 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).
|| An object to which char sequences and values can be appended.
|| A resource that must be closed when it is no longer needed.
|| A CharSequence is a readable sequence of
|| A class implements the
Cloneable interface to indicate to the
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 "for-each loop" statement.
|| A Readable is a source of characters.
Runnable interface should be implemented by any class whose instances are intended to be executed by a thread.
|| Interface for handlers invoked when a Thread abruptly terminates due to an uncaught exception.
|| The Boolean class wraps a value of the primitive type
boolean in an object.
Byte class wraps a value of primitive type
byte in an object.
Character class wraps a value of the primitive type
char 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 class
Class represent classes and interfaces in a running Java application.
|| A class loader is an object that is responsible for loading classes.
|| Does nothing on Android.
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.
Float class wraps a value of primitive type
float in an object.
|| 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 class wraps a value of the primitive type
int in an object.
Long class wraps a value of the primitive type
long in an object.
|| The class
Math contains methods for performing basic numeric operations such as the elementary exponential, logarithm, square root, and trigonometric functions.
|| The abstract class
Number is the superclass of classes
Object is the root of the class hierarchy.
Package objects contain version information about the implementation and specification of a Java package.
Runtime.exec methods create a native process and return an instance of a subclass of
Process that can be used to control the process and obtain information about it.
|| This class is used to create operating system processes.
|| 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.
|| Legacy security code; do not use.
|| Legacy security code; do not use.
Short class wraps a value of primitive type
short in an object.
|| An element in a stack trace, as returned by
|| The class
StrictMath contains methods for performing basic numeric operations such as the elementary exponential, logarithm, square root, and trigonometric functions.
String class represents character strings.
|| A thread-safe, mutable sequence of characters.
|| A mutable sequence of characters.
System class contains several useful class fields and methods.
|| A thread is a thread of execution in a program.
|| A thread group represents a set of threads.
|| This class provides thread-local variables.
Throwable class is the superclass of all errors and exceptions in the Java language.
Void class is an uninstantiable placeholder class to hold a reference to the
Class object representing the Java keyword void.
|| 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:
forName method in 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
|| Thrown when an application tries to access an enum constant by name and the enum type contains no constant with the specified name.
|| The class
Exception and its subclasses are a form of
Throwable 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 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 the
newInstance method in class
Class, 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 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 use
null 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 by
String 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.
|| Thrown when an application tries to call an abstract method.
|| Thrown to indicate that an assertion has failed.
|| 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.
Error is a subclass of
Throwable 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 Java
new construct to instantiate an abstract class or an interface.
|| Thrown to indicate some unexpected internal error has occurred in the Java Virtual Machine.
|| 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.
|| 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.
|| 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 of
ThreadDeath is thrown in the victim thread when the (deprecated)
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 declared
|| 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.