reference or value about Java

[Chen SanHau]

I don't know how to give the subject of my question. I'm a new learner about Java. I would be very appreciated of your help !!

01 public class Test { 
02   public static void main(String[] args){ 
03      Test t = new Test(); 
04      t.first(); 
05   } 
06
07   public void first(){ 
08      int i =5; 
09      Value v = new Value(); 
10      v.i = 25; 
11      second(v, i); 
12      // v.i= 20    :confused:    Why??? That's my question.....
13      System.out.println("v.i= " + v.i);  
14   } 
15
16   public void second(Value v, int i){ 
17      i = 0 ; 
18      v.i= 20; 
19      Value val= new Value(); 
20      v = val; 
21      System.out.println("v.i= " + v.i + "; i=  " + i);  // v.i=15; i=0 
22   } 
23 } 
24
25  class Value { 
26    public int i = 15; 
27  } 

Line 12 is my question?
I hope your help!!!
Thanx!!
[ February 06, 2004: Message edited by: Ha LoHa ]
[ February 06, 2004: Message edited by: Ha LoHa ]

[Ernest Friedman-Hill]

A variable is a reference to an object; it's not the object itself. If you assign a variable to point to a new object, then any old object it pointed to is still there, and any other variables that pointed to it still point to it.
So in "first" you pass a reference to a Value object to the method "second". "second" sets the member "i" of that Value object to 20, then makes the reference point to another Value object and manipulates this different object. "first" still holds a reference to the original Value, the one with 20 in its "i" member.
See the JavaRanch "Campfire Stories" for more information; in particular, take a few minutes to read this one.

[Chen SanHau]

Thank your help !!!