Sharing code examples illustrating Java's delivery and callback mechanism-javaTutorial-php.cn

Sharing code examples illustrating Java's delivery and callback mechanism

高洛峰

Release： 2017-01-24 13:38:50

Original

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Java pass by value or by reference
1. Original type parameter passing

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

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2. Reference type parameter passing

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);
}

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Run these two programs, I believe you will understand: Java manipulates objects 'by reference,' but it passes object references to methods 'by value.

java callback mechanism
spring uses the java callback mechanism extensively , the following is a brief introduction to the Java callback mechanism:

In a word, callback is a two-way calling mode. What does it mean? That is, the callee will also call the other party when it is called. This It's called a callback. "If you call me, I will call back."

Look at the following example about the callback mechanism:

Interface CallBackInterface:

public interface CallBackInterface {
 void save();
}

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Class ClassB:

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());
 }
 
}

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ClassClassA:

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!");
 }
}

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A more classic example of the use of callback functions (using java anonymous classes) omits the source code here

More instructions for Java Please pay attention to the PHP Chinese website for related articles sharing code examples of the delivery and callback mechanism!