Java 回调机制

Class A实现接口CallBack callback——背景1
class A中包含一个class B的引用b ——背景2
class B有一个参数为callback的方法f(CallBack callback) ——背景3


1. 异步的回调机制

public interface CallBack {
	public abstract void solve(String result);
}

public class Wang implements CallBack {

	private Li li;
	public Wang(Li li) {
		this.li = li;
	}
	
	public void askQuestion(final String question) {
		System.out.println("ask question : ");
		new Thread(new Runnable() {
			@Override
			public void run() {
				li.executeMessage(Wang.this, question);
			}
		}).start();
		
		play();
		
	}
	
	public void play() {
		System.out.println("i am out to do something.");
	}
	
	@Override
	public void solve(String result) {
		System.out.println("The answer is " + result);
	}

}

public class Li {

	public void executeMessage(CallBack callBack, String question) {
		System.out.println("the question is :" + question);
		for (int i=0; i<10000; i++) {
			
		}
		
		String result = "the answer is 2";
		callBack.solve(result);
	}
}

public class TestLi {

	public static void main(String[] args) {
		Li li = new Li();
		Wang wang = new Wang(li);
		wang.askQuestion("1+1 = ? ");
	}
	
}

interface CallBack{   //相当于接口InA  
    public void doCRUD();     
}    
  
public class A implements CallBack{//【背景1】  
    private B b;//【背景2】  
    public void doCRUD(){    
          System.out.println("执行add操作...");    
     }    
  
     public void add(){    
             b.execute(new A());//【you call me】    
        }    
}  
  
public class B{  
     public void execute(CallBack action){  //【背景3】  
            getConnection();    
            action.doCRUD();  //【i call you back】  
            releaseConnection();    
        }    
  
      public void getConnection(){    
            System.out.println("获得连接...");    
        }    
            
        public void releaseConnection(){    
            System.out.println("释放连接...");    
        }    
}