Structural Design Pattern : Composite

Composite Design Pattern:

Word composite mean object contain another object.

Composite Pattern is Tree Structure of simple and composite objects to represent part-whole hierarchy.

Classic real time Example is the Family hierarchy. Lets try to put it into some design

( Click to enlarge)

Code:

Component:

package com.milind.gof.structural.composite;

/**

*

* @author milind

*/

public interface Family {

public void print();

}

Composite:

package com.milind.gof.structural.composite;

import java.util.ArrayList;

/**

*

* @author milind

*/

public class Parnet implements Family{

private String name;

private ArrayList arr;

public Parnet(String name) {

this.name = name;

this.arr = new ArrayList() ;

}

public void addChild(Family ch) {

this.arr.add(ch);

}

public void print() {

for(Family c : arr) {

System.out.println(c);

if(c instanceof Parnet) {

c.print();

}

}

}

@Override

public String toString() {

return "Parent: "+this.name;

}

}

Leaf:

package com.milind.gof.structural.composite;

/**

*

* @author milind

*/

public class Child implements Family{

private String name;

public Child(String name) {

this.name = name;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

@Override

public String toString() {

return "Child: "+ this.name;

}

public void print() {

}

}

Client:

package com.milind.gof.structural.composite;

/**

*

* @author milind

*/

public class Main {

/**

* @param args the command line arguments

*/

public static void main(String[] args) {

Parnet dhirubhai = new Parnet("Dhirubhai");

Parnet anil = new Parnet("Anil");

Parnet mukesh = new Parnet("Mukesh");

Child anil_1 = new Child("Anil_1");

Child anil_2 = new Child("Anil_2");

Child M1 = new Child("M1");

Child M2 = new Child("M2");

//Adding Anil children

anil.addChild(anil_1);

anil.addChild(anil_2);

//Adding Mukesh Children

mukesh.addChild(M1);

mukesh.addChild(M2);

//Adding anil and Mukesj to dhirubhai.

dhirubhai.addChild(anil);

dhirubhai.addChild(mukesh);

//printing dhirubhia's family.

dhirubhai.print();

}

}