Why my ''else'' doesn't work?

Question

import javax.swing.*;


public class Password {
  public static void main(String [] args)
  {
    String password;
    do
    {
      password=JOptionPane.showInputDialog("Password, Please");

      if(password==("N123U"));


      JOptionPane.showMessageDialog(null,"Welcome");

      else
      JOptionPane.showMessageDialog(null,"Try again");

    }while(password.equals("N123U")==false);
  }

}

Dennis, while you're probably right, it's likely that the poster did not assume the issue was related to string comparison (and in fact it isn't fully related to that). — Giulio Franco, Nov 02 '13 at 00:54

score 3 · Answer 1 · answered Nov 02 '13 at 00:51

3

You have a semicolon at the end of your if statement. Having that ends the if statement. Remove it, if statements should not have a semicolon.

answered Nov 02 '13 at 00:51

shf301

31,086
2
52
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score 2 · Answer 2 · answered Nov 02 '13 at 00:55

The other answers are correct, you have a ; at the end of your if statement, but so you can see...

 if(password==("N123U"));
                        ^--- This is your problem...

This is one of the reasons why it is recommend to always use braces around your statements, even if they are a single line...

 if(password==("N123U")) {
     JOptionPane.showMessageDialog(null,"Welcome");
 } else {
     JOptionPane.showMessageDialog(null,"Try again");
 }

The other problem you are (going) to have is the fact that you are using == to compare Strings, which is only comparing the object references, which is unlikely to be equal. Instead you should be using String#equals, for example...

if("N123U".equals(password)) {...}

Which will also help you avoid NullPointerExceptions

Floris · Answer 3 · 2013-11-02T00:56:34.737

Semicolon after if signifies end of statement: the next line is not considered part of the if clause. Remove the semicolon to get the right flow. In other words,

if(password==("N123U"));

Should be

if(password==("N123U")) {
  // do something
}
else {
  // do something else
}

In principle when each of the if and else are single statements you can omit the curly braces, but that is usually asking for trouble at some point in your future...

score 0 · Answer 4 · answered Nov 02 '13 at 00:53

0

  if(password==("N123U"));

Two thing wrong. Shouold be

  if("N123U".equals(password))

  // don't compare strings with == and you have a semicolon, ending the statement

answered Nov 02 '13 at 00:53

Paul Samsotha

205,037
37
486
720

score 0 · Answer 5 · answered Nov 02 '13 at 00:56

I guess, there are two errors: you try to compare a string with "==" in Java - always use .equals for Strings, like you do in the "while" part. The "if" part is terminated by the semicolon - let me try to correct that code:

import javax.swing.*;

public class Password {
  public static void main(String [] args)
  {
    String password;
    do
    {
      password=JOptionPane.showInputDialog("Password, Please");

      if(password.equals("N123U")) {


      JOptionPane.showMessageDialog(null,"Welcome");

      } else {
          JOptionPane.showMessageDialog(null,"Try again");
      }

    }while(password.equals("N123U")==false);
  }

}

score 0 · Answer 6 · answered Nov 02 '13 at 00:56

Actually, if you'd just put a block around the "then" statement (even if it's just that one line), the error would be more obvious (visually that is).

For future reference: a single ; is an empty (aka "do nothing") statement. So what you tell your programm to do is (pseudo-code):

if (something)
    <do nothing>
JOptionPane.doSomething()
else // <- syntax error here, we're not in an if anymore, so this is invalid
    ...
...

Why my ''else'' doesn't work?

6 Answers6