Able to change Static variable value

Question

As mentioned in the below link Link

Static variables are initialized only once, at the start of the execution. These variables will be initialized first, before the initialization of any instance variables.
A single copy to be shared by all instances of the class.

But i am able to change the value of static variable

class Test {
  static int a =10;
  public static void main(String args[])
  {
    a=20;
    System.out.println("rest of the code...");
    Test1 t= new Test1();
    t.m();
  }
}

public class Test1 {
    void m () 
     {
         System.out.println(Test.a);
     }
}

initialize = set initial value. It doesn't mean that this value can't be changed later. — Bogdan Lukiyanchuk, Apr 22 '18 at 18:26
if you want the value of your variable can't be changed make it final — Bogdan Lukiyanchuk, Apr 22 '18 at 18:27
i know about final..i just want to know then whats the practical use of static varibale — Rahul, Apr 22 '18 at 18:28
If you know about final, then why are you asking why the value can be changed? — OneCricketeer, Apr 22 '18 at 18:33
When you need a static variable. Like shared by instances or other classes, e.g., a reference value. — Dave Newton, Apr 22 '18 at 18:36

Paco Abato · Accepted Answer · 2018-04-22T18:40:32.860

The definition means that the variable will be initialized only once in a context of the class definition. Id est, for the class Test in your example it will be initialized only once no matter the number of objects you instantiate for this class.

Take also into account that initialization is not the same as changing the value of the variable later.

To ilustrate your question in comments:

class Test {
    public static long staticAtr = System.currentTimeMillis();
    public long nonStaticAtr = System.currentTimeMillis();

    public static void main(String[] args) {

        Test t1 = new Test();
        Thread.sleep(100);
        Test t2 = new Test();
        System.out.println(t1.staticAtr);
        System.out.println(t1.nonStaticAtr);
        System.out.println(t2.staticAtr);
        System.out.println(t2.nonStaticAtr);
}

t1 and t2 show the same staticAtr that was initialized only once at the start of the execution, while the nonStaticAtr of t1 and t2 where initialized once per instantiation and have therefor different values.

No, only static ones. The non-static variables will be initialized once per instantiation. — Paco Abato, Apr 22 '18 at 18:33

score 0 · Answer 2 · edited Apr 22 '18 at 18:35

0

What is meant by the quoted rule is that when you create instance A of class Test and this initialized member a with 10. If you now change the value of a in A to .e.g 12, the next created class, as well as all previous instances, will see a having a value of 12.

edited Apr 22 '18 at 18:35

OneCricketeer

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answered Apr 22 '18 at 18:31

CannedMoose

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Able to change Static variable value

2 Answers2