public void badSwap(int var1, int var2)  
{ 
int temp = var1;  
var1 = var2;  
var2 = temp; 
} 

public void tricky(Point arg1, Point arg2) 
{ 
 arg1.x = 100; 
 arg1.y = 100; 
 Point temp = arg1; 
 arg1 = arg2; 
 arg2 = temp; 
} 
public static void main(String [] args) 
{ 
 Point pnt1 = new Point(0,0); 
 Point pnt2 = new Point(0,0); 
 System.out.println("X: " + pnt1.x + " Y: " +pnt1.y); 
 System.out.println("X: " + pnt2.x + " Y: " +pnt2.y); 
 System.out.println(" "); 
 tricky(pnt1,pnt2); 
 System.out.println("X: " + pnt1.x + " Y:" + pnt1.y); 
 System.out.println("X: " + pnt2.x + " Y: " +pnt2.y); 
} 

public interface CallBackInterface {
 void save();
}

public class ClassB implements CallBackInterface {

public void save() {
System.out.println("执行保存操作!");
}
//
public void add()
{

    //这里调用ClassA的方法 同时ClasssB又会回调ClassB的save方法
    new ClassA().executeSave(new ClassB());
 }

}

public class ClassA {

 public void executeSave(CallBackInterface callBackInterface)
 {
 getConn();
 callBackInterface.save();  //you call me
 realse();
 }
 public void getConn()
 {
 System.out.println("获取数据库连接!");
 }
 public void realse()
 {
 System.out.println("释放数据库连接!");
 }
}