This post shows 2 sets of rather equivalent Java source codes. One uses inheritance that enable child classes to inherit properties and methods from their parent classes. Another set uses the Delegation Design Pattern.

Inheritance

[wp_ad_camp_1]

With inheritance, we use the extends keyword in Java. The PitBull class will have the name property and getter/setter methods PLUS strayOrNot and its associatd getter/setter methods.

class Dog {
    private String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    } 
}

class PitBull extends Dog{

    private boolean strayOrNot;

    public boolean isStrayOrNot() {
        return strayOrNot;
    }

    public void setStrayOrNot(boolean strayOrNot) {
        this.strayOrNot = strayOrNot;
    }
}

class Dog {

private String name;

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

class PitBull extends Dog{

private boolean strayOrNot;

public boolean isStrayOrNot() {

return strayOrNot;

}

public void setStrayOrNot(boolean strayOrNot) {

this.strayOrNot = strayOrNot;

}

Delegation Pattern

[wp_ad_camp_2]

Put simply, the class which other classes supposedly inherits their properties and methods from is made a reference variable in those “child” classes. Method calls are routed accordingly to call methods on an object of that reference variable type.

For example,

class Dog {
    private String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    } 
}

class PitBull {
    private Dog dog;

    private boolean strayOrNot;

    public boolean isStrayOrNot() {
        return strayOrNot;
    }

    public void setStrayOrNot(boolean strayOrNot) {
        this.strayOrNot = strayOrNot;
    }

    public String getName() {
        return dog.getName();
    }

    public void setName(String name) {
        this.dog.setName(name);
    } 
}