Java™ How to Program, Seventh Edition

17.2. Type-Wrapper Classes for Primitive Types

Each primitive type (listed in Appendix D, Primitive Types) has a corresponding type-wrapper class (in package java.lang). These classes are called Boolean, Byte, Character, Double, Float, Integer, Long and Short. Each type-wrapper class enables you to manipulate primitive-type values as objects. Many of the data structures that we develop or reuse in Chapters 17–19 manipulate and share Objects. These classes cannot manipulate variables of primitive types, but they can manipulate objects of the type-wrapper classes, because every class ultimately derives from Object.

Each of the numeric type-wrapper classes—Byte, Short, Integer, Long, Float and Double—extends class Number. Also, the type-wrapper ...