Classes and objects in Java - JavaTech: An Introduction to Scientific and Technical Computing with Java - page 74

Table 3.1 Primitives and their wrapper classes.

Primitive Wrapper

boolean java.lang.Boolean

byte java.lang.Byte

char java.lang.Character

short java.lang.Short

int java.lang.Integer

long java.lang.Long

float java.lang.Float

double java.lang.Double

Table 3.1 lists the primitive types and the corresponding wrapper classes. See
the Java 2 Platform API Specification for detailed listings and descriptions of the
methods and constants provided with each of the wrapper classes.
With the exception of java.lang.Character and java.lang.
Integer , the wrappers have the exact same name as the corresponding primi-
tive type but with the first letter capitalized. The wrappers are normal classes that
inherit from the Object superclass like all Java classes (see Chapter 4).
The wrapper constructors create class objects from the primitive types. For
example, for a double floating-point number d:

double d = 5.0;
Double wrapper - double = new Double (d);
Here a Double wrapper object is created by passing the double value to the
Double constructor.
In turn, the wrapper provides a method to return the primitive value

double r = wrapper - double.doubleValue ();
Each wrapper class has a similar method to access the corresponding primitive
value: intValue() for Integer , booleanValue() for Boolean , etc. There
are additional convenience methods to return other types to which the wrapped
primitive could be converted. For example, Integer.longValue() returns
the value of the Integer as a long type, Integer.byteValue() returns
the value as a byte type, etc. Since nothing casts to or from a boolean primitive
type, the Boolean wrapper has only the booleanValue() method.

3.7.1 Strings, wrappers and primitives
The wrappers for primitive types also provide a number of useful static methods
including some to convert numbers to strings and vice versa. These are very
useful when reading textual input that needs to be converted to a primitive type.
A common situation where these come in handy involves passing numbers to