设计模式之---组合模式

定义

Compose objects into tree structures to represent part-whole hierarchies. Composite lets clients treat individual objectsand compositions of objects uniformly.
将对象组合成树形结构以表示“部分-整体”的层次结构，组合模式使得用户对单个对象和组合对象的使用具有一致性。
类图：略
从类图组合模式主要三个功能类

抽象构建类 Component
叶子构建类 Leaf
树枝构建类 Composite

优点

便于业务层的调用
叶子和树枝构件自由增加

缺点

和依赖倒置原则相违背，因为其依赖了具体的实现类
代码

public abstract class Component {
    public void doSomething(){

    }
}

public class Composite extends Component {
    private List components=new ArrayList();
 public void add(Component component){
        this.components.add(component);
  }
    public void remove(Component component){
        this.components.remove(component);
  }
    public List getChildren(){
        return this.components;
  }

    @Override
  public void doSomething() {
        super.doSomething();
  System.out.println("我是父节点");
  }
}

public class Leaf extends Component {
    @Override
  public void doSomething() {
        super.doSomething();
  System.out.println("我是叶构件");
  }
}

测试类

public class Test {
    public static void main(String[] args) {
        Composite root=new Composite();
  Composite branch=new Composite();
  Leaf leaf=new Leaf();
  root.add(branch);
  branch.add(leaf);
  display(root);

  }
    public static void display(Composite root){
        for (Component c:root.getChildren()){
            if(c instanceof Leaf){
                c.doSomething();
  }else{
                display((Composite) c);
  }
        }
    }
}

输出结果

我是叶构件

参考：百度百科