Strange question,Help me, always got the same value

Question

Hi,
I write a program, have following code:
public class T{
private int iNum=0;
public T(){};
public void do_a(){
iNum++;
System.out.println("---Num="+iNum);
public void do_b(){
System.out.println("---Show Num="+iNum);
public static void main(String []args){
T t=new T();
do_a(); //ok, result is right, ---Num=1
do_b(); //ok, result is right, ---Num=1
when i use this class with other class, function do_a() is correct,
but do_b() always show "---Show Num=0",
why, i can't think it out, so strange,
any advice is kind of you!

Answer 1

Your problem is that you are not using the object you have created. The statement:
T t = new T();Creates a new instance object of the type T. Having created this object I assume that you want to call the methods attached to this object. To do that you have to add at the beginning of any method call the name of the object and a dot eg.
do_a();//This accesses the method from a static context
t.do_a();//This will access the method and increment the variables contained within the instance tHowever even if you are accessing this object from a static context then the value iNum is still incremented. But you will need to add the keyword static to the method declarations of do_a() and do_b() so that they can be run from main().