I am confused

[Nakul P. Patel]

package Test;

class Test{
    int a;
    Test(int i){
        System.out.println("Value of a is:"+a); //Every time value of a is: 0!!! ---it makes me confused,please explain this.
        a=i;
        System.out.println("Value of A is:"+a);//value of A is 12???---if a is 0,than 0+10 is 12??? 
    }
    Test incr(){
        Test temp= new Test(a+10);
        return temp;
    }
}
public class Main{

    public static void main(String[] args) {
        Test ob1 = new Test(2); 					
        Test ob2,ob3;
        ob1.incr();	
        System.out.println("ob1.a:"+ob1.a);		
        ob2=ob1;						
        ob2.incr();				
        System.out.println("ob2.a:"+ob2.a); 
        ob3=ob2.incr();		
        System.out.println("ob2.a after second increment"+ob3.a); 
    }
}

/*
Value of a is:0
Value of A is:2
Value of a is:0
Value of A is:12
ob1.a:2
ob2.a:12
Value of a is:0
Value of A is:22
ob2.a after second increment22
*/

[Matthew Brown]

Try tracing through the code like this:

- Line 18 creates a new Test, passing in i = 2. That prints the initial value of a (= 0), then adds 2 to that and prints that. So a = 2.
- Line 20 calls incr() on that first Test. This creates a new Test, passing in i = 12. Again, this prints the initial value of a (remember it's a new object, so it's zero again), then adds 2 to that and prints that. So a = 12.
- Etc. Remember that each call to incr creates a new Test object.

(I think you're missing part of the output)

[Nakul P. Patel]

hi,mathew.
First,I want to thank you.I am new to java,and confused.
But you are genius and a good teacher also.
Thank you,again.

[Matthew Brown]

You're welcome .

[dennis deems]

I think you're going to want to spend some time -- a couple months, at the least -- with a beginning Java book, before you jump into the deep end studying SCJP. Otherwise you are going to be very, very frustrated.