No exception still not coming out of while loop

Question

Following is my java code block i am not able to come out of while block, the same code run's perfect in other module. kindly help me

public void current_ER(View v){
        try{ 
                String[] parameters= {uid};
                Caller c=new Caller();

                c.url="current_ER.php";
                c.parameters=parameters;
                c.join(); c.start();

                String result=MainActivity.result;
                System.out.print("before while");
                while(result=="START") {
                    try {
                          Thread.sleep(10); 
                          System.out.print(result); 
                    }
                    catch(Exception ex) { 
                          ex.getLocalizedMessage();
                    System.out.print("in catch"); 
                    }
                }
                System.out.print("after while");    
                Toast.makeText(this, "ER Details->"+result , Toast.LENGTH_LONG).show();
                {                   
                    System.out.print("before start indent block");
                    /////////to next screen////
                    Intent Manage_Expense=new Intent(this,Manage_Expense.class);
                    Manage_Expense.putExtra("er_details", result);
                    //MainActivity.result="START";
                    Toast.makeText(this, "ER Details->"+result , Toast.LENGTH_LONG).show();
                    //startActivity(Manage_Expense);
                }

}catch(Exception e){
                System.out.println(e.getMessage());

}

    };

[When a developer compare strings with `==`, He cries :)](http://stackoverflow.com/questions/17443201/why-doesnt-work-on-string/17443215#17443215) — Suresh Atta, Dec 24 '13 at 13:05
You never change the value of result in your loop either, does another thread change it? — Tim B, Dec 24 '13 at 13:11
i have replaced my code while("START".equals(result)) but still i am not able to get next line out of while loop — Kunal Kor, Dec 24 '13 at 13:14

BobTheBuilder · Accepted Answer · 2013-12-24T13:31:46.427

4

First of all, use:

while("START".equals(result))

In order to compare Strings.

The main error is that you never update result.

At first you set:

String result=MainActivity.result;

So result and MainActivity.result points to the same object. However, in the other thread you update:

MainActivity.result=resp;

Causing MainActivity.result to point to resp, but result still points to previous value.

If you want to check a variable in a loop, you must make sure the value is changed inside the loop.

edited Dec 24 '13 at 13:31

answered Dec 24 '13 at 13:05

BobTheBuilder

18,858
6
40
61

2

You're too fast for me is who you are! +1 – RossC Dec 24 '13 at 13:05
1

no thats too not working – Kunal Kor Dec 24 '13 at 13:13
Where do you update `result` value? – BobTheBuilder Dec 24 '13 at 13:17
calling it from thread – Kunal Kor Dec 24 '13 at 13:24
Can you add the code too? – BobTheBuilder Dec 24 '13 at 13:25
public void run(){ try{ rs=new Response_From_Server(); String resp=rs.response_Data(url, parameters); MainActivity.result=resp; }catch(Exception ex) {ex.getLocalizedMessage();} } – Kunal Kor Dec 24 '13 at 13:28
Not here. to the question – BobTheBuilder Dec 24 '13 at 13:28
i tried to add in question it is not accepting more code............and in while loop when i am printing result it shows updated vaule – Kunal Kor Dec 24 '13 at 13:37
And the updated value is "START"? – BobTheBuilder Dec 24 '13 at 13:39
no my default value is "START" and updated is my 'ER NO' – Kunal Kor Dec 24 '13 at 13:40

score 1 · Answer 2 · answered Dec 24 '13 at 13:07

1

When you're going to compare 2 strings it's better to use String.equals(), == operator better works on primitives but not on objects.

answered Dec 24 '13 at 13:07

Ulaga

863
1
8
17

score 0 · Answer 3 · answered Dec 24 '13 at 13:53

0

As well as using String#equals() make sure the variable is marked as volatile so threads can see changes made by other threads.

answered Dec 24 '13 at 13:53

Tim B

40,716
16
83
128

score 0 · Answer 4 · answered Dec 25 '13 at 04:34

i updated my code as follows and it worked 

 System.out.print("before while");
               while("START".equals(MainActivity.result)) {
                    try {
                        Thread.sleep(10); 
                        System.out.print(MainActivity.result); 
                    }catch(Exception ex) { ex.getLocalizedMessage();
                    System.out.print("in catch"); 

                    }
                }

but i am still unable to figure out why my original code didn't work

thanks all for your instant and valuable guidance – Kunal Kor Dec 25 '13 at 04:39 — Kunal Kor, Dec 25 '13 at 04:39

No exception still not coming out of while loop

4 Answers4