组合模式

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组合模式本质上是构造类似树形结构，一般用在后台管理系统的菜单

第一步，先创建一个抽象类

public abstract class Component {
    protected String name;

    public Component(String name) {
        this.name = name;
    }

    public  abstract void doSomthing();
}

实现抽象类实例，并且里面放置容器（装载自己实现的抽象父类)

public class Composite extends Component{
    public Composite(String name) {
        super(name);
    }

    @Override
    public void doSomthing() {
        System.err.println("CCCC");
    }


    protected List<Component> components =new ArrayList<>();



    public List<Component> getComponents() {
        return components;
    }

    public void add(Component component){
        components.add(component);
    }

    public void delete(Component component){
        components.remove(component);
    }
}

客户端验证场景，通过客户端要用到的具体类，再具体实现（Branch，Root,Leaf）其中printNode 是用来打印节点信息

public class Client {
    public static void main(String[] args) {
        Composite root = new Root("root");
        Composite leaf = new Leaf("leaf");
        Composite branch1 = new Branch("branch1");
        Composite branch2 = new Branch("branch2");
        root.add(branch1);
        root.add(branch2);
        branch1.add(leaf);
        printNode(root,0);
    }


    private static void printNode(Composite component,int depth){
        for (int i = 0; i < depth; i++) {
            System.err.print("--");
        }

        System.err.println(component.name);
        for (Component entity : component.getComponents()) {
            if (entity instanceof Branch) {
                printNode(((Composite) entity),depth+1);

            }else {
                printNode(((Composite) entity),depth+1);
            }
        }

    }
}

具体实现类

public class Root extends  Composite{

    public Root(String name) {
        super(name);
    }

    @Override
    public void doSomthing() {
      //  System.err.println("Root" + name);
    }

    @Override
    public String toString() {
        return "Root{" +
                "name='" + name + '\'' +
                '}';
    }
}

public class Leaf extends Composite{
    public Leaf(String name) {
        super(name);
    }

    @Override
    public void doSomthing() {
      //  System.err.println("Leaf_" + name);
    }

    @Override
    public String toString() {
        return "Leaf{" +
                "name='" + name + '\'' +
                '}';
    }
}

public class Branch extends  Composite{

    public Branch(String name) {
        super(name);
    }

    public List<Component> getComponents() {
        return components;
    }

    public void add(Component component){
        components.add(component);
    }

    public void delete(Component component){
        components.remove(component);
    }

    @Override
    public void doSomthing() {
       // System.err.println("Branch_"+name);
    }

    @Override
    public String toString() {
        return "Branch{" +
                "name='" + name + '\'' +
                '}';
    }
}