设计模式—组合模式

定义

将对象组合成树形结构以表示“部分-整体”的层次结构，使得用户对单个对象和组合对象的使用具有一致性

代码

抽象通用功能

1
2
3
4
5
public abstract class Component {
    public void doSomething(){
        System.out.println("do something");
    }
}

叶子构件

1
2
3
4
5
6
public class Leaf extends Component {
    @Override
    public void doSomething() {
        System.out.println("leaf do something");
    }
}

树枝构件

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
public class Composite extends Component {
    private ArrayList<Component>   componentArrayList = new ArrayList<>();

    public void add(Component component){
        this.componentArrayList.add(component);
    }

    public void remove(Component component){
        this.componentArrayList.remove(component);
    }

    public ArrayList<Component> getChildren() {
        return this.componentArrayList;
    }
}

测试

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
public class CompositeTest {

    @Test
    public void testComposite(){
        //根
        Composite root = new Composite();
        //枝
        Composite branch = new Composite();
        //叶
        Leaf leaf = new Leaf();
        root.add(branch);
        branch.add(leaf);

        display(root);
    }

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