java

组合就是拿着一个类做另一个类的成员变量

Computer类

package composite;


//组合
public class Computer {
    //组合就是拿着一个类做另一个类的成员变量
    private Cpu cpu = new Cpu();
    private Memory memory = new Memory();
    private MainBoard mainBoard = new MainBoard();

    public void work(){
        cpu.calc();
        cpu.control();
        memory.store();
        mainBoard.connect();
    }

    public static void main(String[] args) {
        Computer computer = new Computer();
        computer.work();
    }
}

Cpu

package composite;

public class Cpu {
    public void calc(){
        System.out.println("=========Cpu calc()===========");
    }

    public void control(){
        System.out.println("=========Cpu control()===========");
    }
}

Memory

package composite;

public class Memory {
    public void store(){
        System.out.println("=========Memory  store()===========");
    }

}

MainBoard

package composite;

public class MainBoard {
    public void connect(){
        System.out.println("=========MainBoard   connect()===========");
    }
}

结果

=========Cpu calc()===========
=========Cpu control()===========
=========Memory  store()===========
=========MainBoard   connect()===========

组合灵活的地方
AMDCpu

package composite;

public class AMDCpu extends Cpu{
    @Override
    public void calc() {
        System.out.println("=====AMDCpu calc()=====");
    }
}

IntelCpu

package composite;

public class IntelCpu extends Cpu {
    @Override
    public void calc() {
        System.out.println("=====IntelCpu calc()=====");
    }
}

此时的Computer使用其他类型的Cpu

package composite;


//组合
public class Computer {
    //组合就是拿着一个类做另一个类的成员变量
    private Cpu cpu = new Cpu();
    private Memory memory = new Memory();
    private MainBoard mainBoard = new MainBoard();


    //注入CPU  使用set方法或者构造方法来给cpu赋新值
    public void setCpu(Cpu cpu){
        this.cpu=cpu;
    }

    public void work(){
        cpu.calc();//这样这里就不用改也能使用IntelCPU了
        cpu.control();
        memory.store();
        mainBoard.connect();
    }

    public static void main(String[] args) {
        Computer computer = new Computer();
        Cpu cpu = new IntelCpu();
        computer.setCpu(cpu);//此时输出=====IntelCpu calc()=====
        computer.work();
    }
}