比较典型的java回调案例-员工老板

下面是一个典型的回调案例：公司员工工作，工作完成后主管要求员工汇报工作完成情况。

  事件接口：

Java代码 

package com.wxy.callback; 

 

public interface Event { 

    /**

     * 返回发生事件信息

     * @return 事件信息

     */ 

    public String happendEvent(); 

 

} 

   事件具体实现类：

Java代码 

package com.wxy.callback; 

 

public class EventA implements Event { 

 

    @Override 

    public String happendEvent() { 

        return "job has been finished!"; 

    } 

 

} 

 

Java代码 

package com.wxy.callback; 

 

public class EventB implements Event { 

 

    @Override 

    public String happendEvent() { 

        return "job has been finished!"; 

    } 

 

} 

 主管类：

Java代码 

package com.wxy.callback; 

 

public class Boss { 

    private String name; 

 

    public Boss(String name) { 

        this.name = name; 

    } 

 

    public void getStaffEvent(Staff staff, Event event) { 

        System.out.println("the msg what the boss received is--" + staff.getName() + ":" 

                           + event.happendEvent()); 

    } 

 

    public String getName() { 

        return name; 

    } 

 

    public void setName(String name) { 

        this.name = name; 

    } 

 

} 

 员工类：

Java代码 

package com.wxy.callback; 

 

public class Staff { 

    private Event  event; //事件 

    private String name; //员工姓名 

    private Boss   boss; //员工所属主管 

 

    /**

     * 员工构造器  

     * @param name 员工姓名

     * @param boss 传入Boss对象，便于回调反馈工作状况

     */ 

    public Staff(String name, Boss boss) { 

        this.name = name; 

        this.boss = boss; 

    } 

 

    public void doWork() { 

        System.out.println(name + " is doing working..."); 

        //do somtething..... 

        for (int i = 0; i < 10; i++) { 

            System.out.println("sheep" + i); 

        } 

        System.out.println(name + " was finished work!"); 

        //tell the boss what has happend,这里就是boss的回调方法 

        boss.getStaffEvent(this, event); 

    } 

 

    public Event getEvent() { 

        return event; 

    } 

 

    public void setEvent(Event event) { 

        this.event = event; 

    } 

 

    public String getName() { 

        return name; 

    } 

 

    public void setName(String name) { 

        this.name = name; 

    } 

 

    public Boss getBoss() { 

        return boss; 

    } 

 

    public void setBoss(Boss boss) { 

        this.boss = boss; 

    } 

 

} 

 测试类：

Java代码 

package com.wxy.callback; 

 

public class StaffBossTest { 

    public static void main(String args[]) { 

        //初始化员工和主管 

        Boss boss = new Boss("boss"); 

        Staff staffA = new Staff("staffA", boss); 

        Staff staffB = new Staff("staffB", boss); 

 

        //主管发放了两个新任务 

        Event event1 = new EventA(); 

        Event event2 = new EventB(); 

 

        //员工接受任务开始干活 

        staffA.setEvent(event1); 

        staffB.setEvent(event2); 

 

        //员工干晚活，及时向主管反馈工作情况 

        staffA.doWork(); 

        staffB.doWork(); 

    } 

} 

 测试结果：

Java代码 

staffA was finished work! 

the msg what the boss received is--staffA:job has been finished! 

staffB is doing working... 

sheep0 

sheep1 

sheep2 

sheep3 

sheep4 

sheep5 

sheep6 

sheep7 

sheep8 

sheep9 

staffB was finished work! 

the msg what the boss received is--staffB:job has been finished! 

 可以看到，当员工完成工作时（即触发某事件时），staff对象调用boss对象的方法，实现回调功能。设计模式中，观察者模式也是一个典型的应用回调机制的例子。