设计模式之组合模式 Composite

 代码实现

//Component（抽象构件）：抽象构件中定义了叶子和容器构件的共同点。比如，有公共的添加删除叶子功能，有显示节点功能。
public abstract class Component {
    protected String name;
    public Component(String name) {
        super();
        this.name = name;
    }
    public abstract void add(Component c);
    public abstract void remove(Component c);
    public abstract void display(int depth);
}

//表示该节点下面没有其他子节点了，就称为叶子
public class Leaf extends Component {
    public Leaf(String name) {
        super(name);
    }
    @Override
    public void add(Component c) {
        System.out.println("leaf no add");
    }
    @Override
    public void remove(Component c) {
        System.out.println("leaf no remove");
    }
    @Override
    public void display(int depth) {
        StringBuffer sb = new StringBuffer("-");
        for (int i = 0; i <= depth; i++) {
            sb.append("-");
        }
        System.out.println(sb.toString()+name);
    }
}

//容器构件，该节点下还有其他子节点，理解为一个容器，里面包含了其他子节点。就叫做容器构件
public class Composite extends Component{
    private List<Component> children = new ArrayList<Component>();
    public Composite(String name) {
        super(name);
    }
    @Override
    public void add(Component c) {
        children.add(c);
    }
    @Override
    public void remove(Component c) {
        children.remove(c);
    }
    @Override
    public void display(int depth) {
        StringBuffer sb = new StringBuffer("-");
        for (int i = 0; i <= depth; i++) {
            sb.append("-");
        }
        System.out.println(sb.toString()+name);
        for (Component com : children) {
            com.display(depth + 2);
        }
    }
}

public static void main(String[] args) {
    Composite root = new Composite("root");
    root.add(new Leaf("Leaf A"));
    root.add(new Leaf("Leaf B"));
     
    Composite comp = new Composite("Composite X");
    comp.add(new Leaf("Leaf XA"));
    comp.add(new Leaf("Leaf XB"));
    root.add(comp);
     
    Composite comp2 = new Composite("Composite XY");
    comp2.add(new Leaf("Leaf XYA"));
    comp2.add(new Leaf("Leaf XYB"));
    comp.add(comp2);
     
    root.add(new Leaf("Leaf C"));
    Leaf leaf = new Leaf("Leaf D");
    root.add(leaf);
//  root.remove(leaf);//这里可以删除某节点
    root.display(1);
}

---root

-----Leaf A

-----Leaf B

-----Composite X

-------Leaf XA

-------Leaf XB

-------Composite XY

---------Leaf XYA

---------Leaf XYB

-----Leaf C

-----Leaf D