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.
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.