观察者模式简单例子

Posted 2021-06-27 你可以当我没名字

观察者模式

核心:在抽象类里有一个 ArrayList 存放观察者们

代码不算完整,那个table的展示省略

package com.cai.observer;

import java.util.ArrayList;
import java.util.List;

/**
 * @Description
 * @Author Cai
 * @Create 2021-06-12-15:34
 */
interface Table {
    void show();
    void notifyData(DataA data);
}

class Table1 implements Table{
    @Override
    public void show() {
        SpreadsheetView.print1();
    }

    @Override
    public void notifyData(DataA data) {
        data.add(this);
    }
}
class Table2 implements Table{
    @Override
    public void show() {
        SpreadsheetView.print2();
    }

    @Override
    public void notifyData(DataA data) {
        data.add(this);
    }
}

abstract class DataA{
    protected List<Table> list = new ArrayList<>();

    public void add(Table table){
        list.add(table);
    }

    public void remove(Table table){
        list.remove(table);
    }

    public abstract void notifyObserver();
}

class SourceData extends DataA{

    @Override
    public void notifyObserver() {
        for (Table table : list) {
            table.show();
        }
    }
}

class SpreadsheetView{
    static void print1(){
        System.out.println("打印图表1");
    }

    static void print2(){
        System.out.println("打印图表2");
    }
}

public class Main{
    public static void main(String[] args) {
        DataA dataa = new SourceData();
        Table table1 = new Table1();
        Table table2 = new Table2();
        table1.notifyData(dataa);
        table2.notifyData(dataa);
        dataa.notifyObserver();
    }
}