Code examples that illustrate the passing and callback mechanisms of Java share _java

Java to pass a value or to pass a reference
1. Original type parameter Pass

public void Badswap (int var1, int var2)  
{ 
int temp = VAR1;  
var1 = var2;  
var2 = temp; 
} 

2. Reference type parameter passing

public void tricky (point arg1, point arg2) 
{ 
 arg1.x = m; 
 Arg1.y = m; 
 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); 
} 

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

Java callback mechanism
Spring uses a large number of Java callback mechanisms, and here's a simple introduction to the Java callback mechanism:

In a word, a callback is a two-way invocation pattern, meaning, that is, the caller will call each other when called, which is called a callback. "If You call me, I'll call back."

Look at the following example of a callback mechanism:

Interface Callbackinterface:

Public interface Callbackinterface {
 void Save ();
}

Class ClassB:

public class CLASSB implements Callbackinterface {public

void Save () {
System.out.println ("Perform save operation!");
the public void Add ()
{

    //) invokes the ClassA method at the same time CLASSSB the Save method
    new ClassA () of CLASSB. Executesave (New CLASSB ());
 }

Class ClassA:

public class ClassA {public

 void Executesave (Callbackinterface callbackinterface)
 {
 getconn ();
 Callbackinterface.save ();  Call me
 realse ();
 }
 public void Getconn ()
 {
 System.out.println ("Get database Connection!");
 public void Realse ()
 {
 System.out.println ("Free database connection!");
 }

A more classical example of the use of callback functions (using Java anonymous classes) eliminates the source code here