组合模式 Composite Pattern 合成模式

compose objects into tree structures to represent part-whole hierarchies.Composite lets clients treat individual objects and 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，使得用户对单个对象和组合对象的使用具有一致性。

抽象构件角色（Component）：该角色定义参加组合对象的共有方法和属性，规范一些默认的行为接口。

package com.DesignPattern.Structural.Composite;
//定义抽象构建接口
public interface Component {
public void operation();
}

叶子构件角色（Leaf）：该角色是叶子对象，其下没有其他的分支，定义出参加组合的原始对象的行为。

package com.DesignPattern.Structural.Composite;
//定义叶子构件
public class Leaf implements Component {
    @Override
    public void operation() {
        //业务逻辑代码
        System.out.println("Leaf operation");
    }
}

树枝构件角色（Composite）：该角色代表参加组合的、其下的分支的树枝对象，他的作用是将树枝和叶子组合成一个树形结构，并定义出管理子对象的方法，如add()、remove()等。

package com.DesignPattern.Structural.Composite;

import java.util.ArrayList;

//定义树枝构件
public class Composite implements Component {
    // 构件容器
    private ArrayList<Component> componentList = new ArrayList<Component>();

    // 添加构件
    public void add(Component component) {
        this.componentList.add(component);
    }

    // 删除构件
    public void remove(Component component) {
        this.componentList.remove(component);
    }

    // 获取子构件
    public ArrayList<Component> getChild() {
        return this.componentList;
    }

    @Override
    public void operation() {
        // 业务逻辑代码
        System.out.println("Composite operation");
    }
}

Client

package com.DesignPattern.Structural.Composite;

public class Client {

    public static void main(String[] args) {
        // 创建一个根节点
        Composite root = new Composite();
        root.operation();
        // 创建树枝节点
        Composite branch = new Composite();
        // 创建叶子节点
        Leaf leaf = new Leaf();
        // 构件树形结构
        root.add(branch);
        branch.add(leaf);
        display(root);
    }

    // 遍历树（递归）
    public static void display(Composite root) {
        for (Component c : root.getChild()) {
            if (c instanceof Leaf) { // 如果节点类型是叶子节点
                c.operation();
            } else { // 树枝节点
                c.operation();
                display((Composite) c); // 递归调用
            }
        }
    }
}

组合模式的实例

Company.java

package com.DesignPattern.Structural.Composite;
//抽象接口
public interface Company {
    //获取信息
    public String getInfo();
}

ConcreteCompany.java

package com.DesignPattern.Structural.Composite;

import java.util.ArrayList;
//树枝节点类
public class ConcreteCompany implements Company {

    private ArrayList<Company> companyList = new ArrayList<Company>();
    private String name;
    private String position;
    private int salary;
    //构造函数
    public ConcreteCompany(String name, String position, int salary) {
        this.name = name;   //姓名
        this.position = position; //职位
        this.salary = salary;   //薪水
    }
    public void add(Company company){
        this.companyList.add(company);
    }
    public void remove(Company company){
        this.companyList.remove(company);
    }
    public ArrayList<Company> getChild(){
        return this.companyList;
    }
    @Override
    public String getInfo() {
        String info="";
        info="名称:"+this.name;
        info=info+"\t职位："+this.position;
        info=info+"\t薪水："+this.salary;
        return info;
    }

}

Employee.java

package com.DesignPattern.Structural.Composite;
//叶子节点类
public class Employee implements Company {

    private String name;
    private String position;
    private int salary;

    public Employee(String name, String position, int salary) {
        this.name = name;
        this.position = position;
        this.salary = salary;
    }

    @Override
    public String getInfo() {
        String info="";
        info="名称:"+this.name;
        info=info+"\t职位："+this.position;
        info=info+"\t薪水："+this.salary;
        return info;
    }

}

ClientDemo.java

package com.DesignPattern.Structural.Composite;

public class ClientDemo {

    public static void main(String[] args){
        //CEO
        ConcreteCompany root=new ConcreteCompany("Hello","CEO",100000);
        //部门经理
        ConcreteCompany developDep=new ConcreteCompany("developDep","研发部经理",12000);
        ConcreteCompany salesDep=new ConcreteCompany("salesDep","销售部经理",12000);
        ConcreteCompany financeDep=new ConcreteCompany("financeDep","财务部经理",12000);
        //部门员工
        Employee e1=new Employee("A","研发部",3000);
        Employee e2=new Employee("B","研发部",3000);
        Employee e3=new Employee("C","销售部",3000);
        Employee e4=new Employee("D","销售部",3000);
        Employee e5=new Employee("E","财务部",3000);
        Employee e6=new Employee("F","财务部",3000);
        //生成树
        root.add(developDep);
        root.add(salesDep);
        root.add(financeDep);
        developDep.add(e1);
        developDep.add(e2);
        salesDep.add(e3);
        salesDep.add(e4);
        financeDep.add(e5);
        financeDep.add(e6);
        System.out.println(root.getInfo());
        display(root);
    }
    //遍历树（递归）
    public static void display(ConcreteCompany root){
        for(Company c:root.getChild()){
            if(c instanceof Employee){  //如果节点类型是叶子节点
                System.out.println(c.getInfo());
            }else{      //树枝节点
                System.out.println("\n"+c.getInfo());
                display((ConcreteCompany)c);    //递归调用
            }
        }
    }
}