Wrapper Classes

For each of the eight primitive data types, the Java API provides a wrapper class whose objects encapsulate values of that type.

int i = 47;                     // int primitive
Integer iObj = new Integer(47); // Wrapper object for an int primitive
Primitive Type Wrapper Class
byte Byte
short Short
int Integer
long Long
char Character
float Float
double Double
boolean Boolean

Why?

  • Many data structures rely on references to objects - but you can't have a reference to a primitive.

  • The wrapper classes provide useful operations and information related to their primitive type.

These classes are in the java.lang package, so no need to import anything to use them.

  • All the wrappers except Character and Boolean extend the abstract class Number; Character and Boolean extend Object.

Wrapper Class Hierarchy

  • All of the wrappers are declared as final classes - you can't extend a wrapper class.

  • You could subclass Number.

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