validate input using try catch

Question

I am trying to validate input text field in java by creating an exceptional error if user does not type in the word specified i.e. admin

        String username;
        int phone1;

        @Override
        public void widgetSelected(SelectionEvent e) {          
            try
            {
            phone1 = Integer.parseInt(phone.getText());
            }
            catch (Exception exe)
            {           
                MessageDialog.openError(shell, "Error","Phone number has to be a number");
                return;
            }

            try
            {
            username = namefield.getText();
               if (username!= "admin") {
                    throw (new Exception());
                }           
            }
            catch (Exception exe)
            {   
                MessageDialog.openError(shell, "Error","The username must be admin");
                return;
            }


            labelresult.setText("The name entered is:"+ username );


            labelresult2.setText("The phone entered is:"+ phone1 );

The one for phone works perfectly

What about for username. What should i do?

@KarthikeyanVaithilingam that does not answer my question completely. since i am talking about try catch. — Omari Victor Omosa, Aug 07 '16 at 09:04
It's generally recommended not to use exceptions to control program flow. — simonv, Aug 07 '16 at 09:05
@simonv i understand it is not recommended. i am in a situation that i have to use it. so i have simplified my question so as to understand try catch statements — Omari Victor Omosa, Aug 07 '16 at 09:07

score 2 · Answer 1 · edited Aug 07 '16 at 09:40

2

You should use:

 if(!username.equals("admin")){
 //your code
 }

To compare string you will have to use equals() method.

As suggested by simon, it is recommended to use:

if(!"admin".equals(username)){
 // your code 
}

In that way it will be null safe.

edited Aug 07 '16 at 09:40

simonv

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answered Aug 07 '16 at 09:04

Pritam Banerjee

17,953
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2

I would recommend reversing this equals check to avoid potential null pointers. – simonv Aug 07 '16 at 09:15

Kaushal28 · Accepted Answer · 2016-08-07T09:17:47.853

2

As @simonv mentioned in comment, Don't use exception to control program flow. But if you are learning try-catch, than you can try this. Also improve your if statement. You are comparing string object. So use equals() method as following:

        try
        {
        username = namefield.getText();
           if (!"admin".equals(username)) {
                throw new Exception("YOUR_MESSAGE_HERE");
            }           
        }
        catch (Exception exe)
        {   
            System.out.println(exe);
            return;
        }

edited Aug 07 '16 at 09:17

answered Aug 07 '16 at 09:06

Kaushal28

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I believe it should be .equals...not .equal – Omari Victor Omosa Aug 07 '16 at 09:17
yes It is .equals() @krushiovida – Kaushal28 Aug 07 '16 at 09:18

validate input using try catch

2 Answers2