Java in a Nutshell, 5th Edition

Name

Package java.lang

Synopsis

The java.lang package contains the classes that are most central to the Java language. Object is the ultimate superclass of all Java classes and is therefore at the top of all class hierarchies. Class is a class that describes a Java class. There is one Class object for each class that is loaded into Java.

Boolean, Character, Byte, Short, Integer, Long, Float, and Double are immutable class wrappers around each of the primitive Java data types. These classes are useful when you need to manipulate primitive types as objects. They also contain useful conversion and utility methods. Void is a related class that defines a representation for the void method return type, but that defines no methods. String and StringBuffer are objects that represent strings. String is an immutable type, while StringBuffer can have its string changed in place. In Java 5.0, StringBuilder is like StringBuffer but without synchronized methods, which makes it the preferred choice in most applications. String, StringBuffer and StringBuilder implement the Java 1.4 interface CharSequence which allows instances of these classes to be manipulated through a simple shared API.

String and the various primitive type wrapper classes all implement the Comparable interface which defines an ordering for instances of those classes and enables sorting and searching algorithms (such as those of java.util.Arrays and java.util.Collections, for example). Cloneable is an important marker ...