Classes Revisited - Learning Java Through Games - page 174

Comparable<FictionalCharacter>

FictionalCharacter

Superhero Villain

FIGURE 8.6: Inheritance hierarchy.

public FictionalCharacter(String name) {
this .name = name;

}

public String getName () {
return name ;
} public void setName( String name)

{

this .name = name;
public abstract double computeStrength() ;

public int compareTo(FictionalCharacter other) {
if (computeStrength() > other . computeStrength() ) {
return 1;
if (computeStrength() < other . computeStrength() ) {
return − 1;
return 0;

}

}

The implements keyword is used to denote that objects of type FictionalCharacter
will be comparable. Note that the interface Comparable is generic. The type parameter de-
scribes the input type of the compareTo method. In other words, since the compareTo
method takes as input an object of type FictionalCharacter ,wemustimplement
Comparable<FictionalCharacter> . The inheritance hierarchy for our example is shown
in Figure 8.6.
Let us now look at the compareTo method. Consider the following call.
if (batman . compareTo(superman) > 0) {
...

}

The method call will return 1 if Batman has more strength, -1 if Superman has more
strength, or 0 if they have equal strength. In this case, batman is the hidden parameter
(or the this object). The other object formal parameter in the compareTo method will
become equal to superman .
First, note that we could have tried to use this alternative syntax for the compareTo
method.
public int compareTo(FictionalCharacter other) {