. Java Design Patterns . Java Design Patterns Composite
Java Design Patterns Composite
Composite Overview
Assemble groups of objects with the same signature.
TeaBags.java - the abstract base class for the composite
import java.util.LinkedList;
import java.util.ListIterator;
public abstract class TeaBags {
LinkedList teaBagList;
TeaBags parent;
String name;
public abstract int countTeaBags();
public abstract boolean add(TeaBags teaBagsToAdd);
public abstract boolean remove(TeaBags teaBagsToRemove);
public abstract ListIterator createListIterator();
public void setParent(TeaBags parentIn) {
parent = parentIn;
}
public TeaBags getParent() {
return parent;
}
public void setName(String nameIn) {
name = nameIn;
}
public String getName() {
return name;
}
}
download source, use right-click and "Save Target As..." to save with a .java extension.
OneTeaBag.java - one composite extension - the "leaf"
import java.util.ListIterator;
public class OneTeaBag extends TeaBags {
public OneTeaBag(String nameIn) {
this.setName(nameIn);
}
public int countTeaBags() {
return 1;
}
public boolean add(TeaBags teaBagsToAdd) {
return false;
}
public boolean remove(TeaBags teaBagsToRemove) {
return false;
}
public ListIterator createListIterator() {
return null;
}
}
download source, use right-click and "Save Target As..." to save with a .java extension.
TinOfTeaBags.java - one composite extension - the "node"
import java.util.LinkedList;
import java.util.ListIterator;
public class TinOfTeaBags extends TeaBags {
public TinOfTeaBags(String nameIn) {
teaBagList = new LinkedList();
this.setName(nameIn);
}
public int countTeaBags() {
int totalTeaBags = 0;
ListIterator listIterator = this.createListIterator();
TeaBags tempTeaBags;
while (listIterator.hasNext()) {
tempTeaBags = (TeaBags)listIterator.next();
totalTeaBags += tempTeaBags.countTeaBags();
}
return totalTeaBags;
}
public boolean add(TeaBags teaBagsToAdd) {
teaBagsToAdd.setParent(this);
return teaBagList.add(teaBagsToAdd);
}
public boolean remove(TeaBags teaBagsToRemove) {
ListIterator listIterator =
this.createListIterator();
TeaBags tempTeaBags;
while (listIterator.hasNext()) {
tempTeaBags = (TeaBags)listIterator.next();
if (tempTeaBags == teaBagsToRemove) {
listIterator.remove();
return true;
}
}
return false;
}
public ListIterator createListIterator() {
ListIterator listIterator = teaBagList.listIterator();
return listIterator;
}
}
download source, use right-click and "Save Target As..." to save with a .java extension.
TestTeaBagsComposite.java - testing the composite
class TestTeaBagsComposite {
public static void main(String[] args) {
System.out.println("Creating tinOfTeaBags");
TeaBags tinOfTeaBags =
new TinOfTeaBags("tin of tea bags");
System.out.println("The tinOfTeaBags has " +
tinOfTeaBags.countTeaBags() +
" tea bags in it.");
System.out.println(" ");
System.out.println("Creating teaBag1");
TeaBags teaBag1 = new OneTeaBag("tea bag 1");
System.out.println("The teaBag1 has " +
teaBag1.countTeaBags() +
" tea bags in it.");
System.out.println(" ");
System.out.println("Creating teaBag2");
TeaBags teaBag2 = new OneTeaBag("tea bag 2");
System.out.println("The teaBag2 has " +
teaBag2.countTeaBags() +
" tea bags in it.");
System.out.println(" ");
System.out.println(
"Putting teaBag1 and teaBag2 in tinOfTeaBags");
if (tinOfTeaBags.add(teaBag1)) {
System.out.println(
"teaBag1 added successfully to tinOfTeaBags");
} else {
System.out.println(
"teaBag1 not added successfully tinOfTeaBags");
}
if (tinOfTeaBags.add(teaBag2)) {
System.out.println(
"teaBag2 added successfully to tinOfTeaBags");
} else {
System.out.println(
"teaBag2 not added successfully tinOfTeaBags");
}
System.out.println("The tinOfTeaBags now has " +
tinOfTeaBags.countTeaBags() +
" tea bags in it.");
System.out.println(" ");
System.out.println("Creating smallTinOfTeaBags");
TeaBags smallTinOfTeaBags =
new TinOfTeaBags("small tin of tea bags");
System.out.println("The smallTinOfTeaBags has " +
smallTinOfTeaBags.countTeaBags() +
" tea bags in it.");
System.out.println("Creating teaBag3");
TeaBags teaBag3 =
new OneTeaBag("tea bag 3");
System.out.println("The teaBag3 has " +
teaBag3.countTeaBags() +
" tea bags in it.");
System.out.println("Putting teaBag3 in smallTinOfTeaBags");
if (smallTinOfTeaBags.add(teaBag3)) {
System.out.println(
"teaBag3 added successfully to smallTinOfTeaBags");
} else {
System.out.println(
"teaBag3 not added successfully to smallTinOfTeaBags");
}
System.out.println("The smallTinOfTeaBags now has " +
smallTinOfTeaBags.countTeaBags() +
" tea bags in it.");
System.out.println(" ");
System.out.println(
"Putting smallTinOfTeaBags in tinOfTeaBags");
if (tinOfTeaBags.add(smallTinOfTeaBags)) {
System.out.println(
"smallTinOfTeaBags added successfully to tinOfTeaBags");
} else {
System.out.println(
"smallTinOfTeaBags not added successfully to tinOfTeaBags");
}
System.out.println("The tinOfTeaBags now has " +
tinOfTeaBags.countTeaBags() +
" tea bags in it.");
System.out.println(" ");
System.out.println("Removing teaBag2 from tinOfTeaBags");
if (tinOfTeaBags.remove(teaBag2)) {
System.out.println(
"teaBag2 successfully removed from tinOfTeaBags");
} else {
System.out.println(
"teaBag2 not successfully removed from tinOfTeaBags");
}
System.out.println("The tinOfTeaBags now has " +
tinOfTeaBags.countTeaBags() +
" tea bags in it.");
}
}
download source, use right-click and "Save Target As..." to save with a .java extension.
Test Results
Creating teaBag1 The teaBag1 has 1 tea bags in it. Creating teaBag2 The teaBag2 has 1 tea bags in it. Putting teaBag1 and teaBag2 in tinOfTeaBags teaBag1 added successfully to tinOfTeaBags teaBag2 added successfully to tinOfTeaBags The tinOfTeaBags now has 2 tea bags in it. Creating smallTinOfTeaBags The smallTinOfTeaBags has 0 tea bags in it. Creating teaBag3 The teaBag3 has 1 tea bags in it. Putting teaBag3 in smallTinOfTeaBags teaBag3 added successfully to smallTinOfTeaBags The smallTinOfTeaBags now has 1 tea bags in it. Putting smallTinOfTeaBags in tinOfTeaBags smallTinOfTeaBags added successfully to tinOfTeaBags The tinOfTeaBags now has 3 tea bags in it. Removing teaBag2 from tinOfTeaBags teaBag2 successfully removed from tinOfTeaBags The tinOfTeaBags now has 2 tea bags in it.
UML
References
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I realy appreciate the Java Patterns on your site. Since I like to play with the examples I simply copied it into text fils and compiled them. I found a few minor problems you may want to know about:
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