Arrays and Array Lists - Java Concepts - page 409

Primitive Type Wrapper Class

byte Byte

boolean Boolean

char Character

double Double

float Float

int Integer

long Long

short Short

Note that the wrapper class names start with uppercase letters, and that two of them
differ from the names of the corresponding primitive type: Integer and
Character .

Each wrapper class object contains a value of the corresponding primitive type. For
example, an object of the class Double contains a value of type double (see Figure
5 ).

Wrapper objects can be used anywhere that objects are required instead of primitive
type values. For example, you can collect a sequence of floating-point numbers in an
ArrayList<Double> .

Figure 5

An Object of a Wrapper Class

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Starting with Java version 5.0, conversion between primitive types and the
corresponding wrapper classes is automatic. This process is called auto-boxing (even
though auto-wrapping would have been more consistent).

For example, if you assign a number to a Double object, the number is
automatically Ȓput into a boxȓ, namely a wrapper object.