组合模式，也称为部分整体模式。是一种结构型设计模式。在组合模式中，将对象组合成树形结构以表示“部分--整体”的层次结构，使得银行对单个对象和组合对象的使用具有一致性。
一般的，在表示对象的部分-整体层次结构时，使用组合模式。或者在从一个整体中能独立出部分模块或功能的场景。下面我们先设计一组安全的组合模式。
1
package compositepatten;
public abstract class Component {
protected String name;
public Component(String name) {
super();
this.name = name;
}
public abstract void doSomething();
}
2
package compositepatten;
import java.util.ArrayList;
import java.util.List;
public class Composite extends Component{
private List<Component> components = new ArrayList<>();
public Composite(String name) {
super(name);
}
public void addChild(Component component){
components.add(component);
}
public Component getChild(int i){
return components.get(i);
}
public void removeChild(Component component){
components.remove(component);
}
@Override
public void doSomething() {
System.out.println(name);
if (null != components) {
for (Component c : components) {
c.doSomething();
}
}
}
}
3
package compositepatten;
public class Leaf extends Component{
public Leaf(String name) {
super(name);
}
@Override
public void doSomething() {
System.out.println(name);
}
}
4
package compositepatten;
public class Client {
public static void main(String[] args) {
//构造一个根节点
Composite root = new Composite("ROOT");
//构造两个支节点
Composite branch1 = new Composite("BRANCH1");
Composite branch2 = new Composite("BRANCH2");
//构造两个叶子节点
Leaf leaf1 = new Leaf("LEAF1");
Leaf leaf2 = new Leaf("LEAF2");
//将叶子节点添加到支节点中
branch1.addChild(leaf1);
branch2.addChild(leaf2);
//将支节点添加到根节点中
root.addChild(branch1);
root.addChild(branch2);
//执行方法
root.doSomething();
}
}
输出结果：
ROOT
BRANCH1
LEAF1
BRANCH2
LEAF2
还有一种透明的组合方式，
1.
package compositepatten;
public abstract class Component {
protected String name;
public Component(String name) {
super();
this.name = name;
}
public abstract void doSomething();
public abstract void addChild(Component component);
public abstract Component getChild(int i);
public abstract void removeChild(Component component);
}
2.
package compositepatten;
import java.util.ArrayList;
import java.util.List;
public class Composite extends Component{
private List<Component> components = new ArrayList<>();
public Composite(String name) {
super(name);
}
public void addChild(Component component){
components.add(component);
}
public Component getChild(int i){
return components.get(i);
}
public void removeChild(Component component){
components.remove(component);
}
@Override
public void doSomething() {
System.out.println(name);
if (null != components) {
for (Component c : components) {
c.doSomething();
}
}
}
}
3.
package compositepatten;
public class Leaf extends Component{
private String message = "叶子节点没有子节点";
public Leaf(String name) {
super(name);
}
@Override
public void doSomething() {
System.out.println(name);
}
@Override
public void addChild(Component component) {
throw new UnsupportedOperationException(message);
}
@Override
public Component getChild(int i) {
throw new UnsupportedOperationException(message);
}
@Override
public void removeChild(Component component) {
throw new UnsupportedOperationException(message);
}
}
4.
package compositepatten;
public class Client {
public static void main(String[] args) {
//构造一个根节点
// Composite root = new Composite("ROOT");
//
Component root = new Composite("ROOT");
//构造两个支节点
Composite branch1 = new Composite("BRANCH1");
Composite branch2 = new Composite("BRANCH2");
//构造两个叶子节点
Leaf leaf1 = new Leaf("LEAF1");
Leaf leaf2 = new Leaf("LEAF2");
//将叶子节点添加到支节点中
branch1.addChild(leaf1);
branch2.addChild(leaf2);
//将支节点添加到根节点中
root.addChild(branch1);
root.addChild(branch2);
//执行方法
root.doSomething();
}
}
输出结果：
ROOT
BRANCH1
LEAF1
BRANCH2
LEAF2