Extending Classes and Inheritance - Beginning Java - page 309

contents of the array of Jacket objects. This also involves an implicit call to the toString() method for
each Jacket object.
Because you have defined the JacketSize and JacketColor enumerations in separate classes, they are
accessible from any source file in the same directory. To make them even more widely available, you
could put them in a package.
The Jacket class uses the enumeration types to define private fields recording the size and color of a
jacket. Note how the toString() method in the Jacket class is able to use the size and color members
as though they were strings. The compiler inserts a call to the toString() method for the enumeration
type that applies. You can override the toString() method for an enumeration type. For example, you
might decide you prefer to define the toString() method in the JacketSize enumeration like this:
@Override
public String toString() {
switch(this) {
case small:
return "S";
case medium:
return "M";
case large:
return "L";
case extra_large:
return "XL";
default:
return "XXL";
}
}
Note how you can use this as the control expression for the switch statement. This is because this
references the current instance, which is an enumeration constant. Because the expression is an enumera-
tion constant, the case labels are the constant names. They do not need to be qualified by the name of the
enumeration. With this implementation of toString() in the JacketSize enumeration, the output is:
Jackets colors available are:
red orange yellow blue green
Jackets sizes available are:
S M L XL XXL
Jackets in stock are:
Jacket M in red
Jacket XL in yellow
Jacket S in green
Jacket XXL in blue
Thus, you can see from this example that you can treat an enumeration type just like any other class type.