Overview Summary |
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.
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. Class | Description |
---|---|
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.
|
Module | |
ModuleLayer |
A layer of modules in the Java virtual machine.
|
ModuleLayer.Controller |
Controls a module layer.
|
Package |
Package objects contain version informationRepresents metadata about the implementation and specification ofa Javarun-time package associated with a class loader. |
StackTraceElement |
An element in a stack trace, as returned by
Throwable.getStackTrace() .
|
Exception | Description |
---|---|
IllegalCallerException |
Thrown to indicate that a method has been called by an inappropriate caller.
|
LayerInstantiationException |
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