How to manually exit a while loop (java)

Question

This code will take user input from the console, and go to one of two places depending on if the input is an Integer or not. The exception is caught and then dealt with by reading it again to get it out of the stream. (not sure if Scanner counts as a stream, but I know that without the input.next() it will never leave that section).

So what I want to know is how can I exit the loop if I get to the MismatchException with a certain input. I've tested the if(bad_input == anything) and it turns out I can never actually get there. I tried some print statements in that block that never executed. Would appreciate any help.

Solved

Not sure how to close the question, but this has been solved. I was incorrectly using == to check two strings. The correct way is to use bad_input.equals("x").

public static void main(String[] args){
  //read input from console
  Scanner input = new Scanner(System.in);

  boolean loop = true;

  while(loop){
    //inputting "1 2 d 1" will evaluate each term separately and output at once
    try{

      //choice = console input only in INTEGER
      int choice = input.nextInt();
      System.out.println("Input was " + choice);

    } catch (InputMismatchException ex){
      //here if input != INTEGER

      String bad_input = input.next();
      System.out.println("Bad Input: " + bad_input);

      //need to figure out how to exit loop!!
      if(bad_input == "x"){
           loop = false;
           return;
      }
      continue;
    }
  }
}

Use break instead of continue, see http://stackoverflow.com/questions/462373/difference-between-break-and-continue-statement — Babak Behzadi, Dec 22 '15 at 06:05
The continue is there for if the "bad input" is something other than the exit condition "x". I want it to continue iterating until I receive the "x". — Peyton C., Dec 22 '15 at 06:21

score 2 · Accepted Answer · edited Dec 22 '15 at 06:31

2

In java String comparison is using equals function "==" might not work

Change

if (bad_input == "x") {
    loop = false;
    return;
}

To

if (bad_input.equals("x")) {
    loop = false;
    return;
}

edited Dec 22 '15 at 06:31

Mandar Pandit

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answered Dec 22 '15 at 06:07

Geo Paul

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This is the one. Thank you very much! – Peyton C. Dec 22 '15 at 06:19

score 2 · Answer 2 · answered Dec 22 '15 at 06:09

2

Try to use break.

if(condition)
    break;

answered Dec 22 '15 at 06:09

hehe

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score 1 · Answer 3 · answered Dec 22 '15 at 06:10

1

break; will exit the loop immediately. What you're doing should also work though. I'm not sure you need the if statement though, the whole catch block will be executed if and only if the input isn't an integer.

answered Dec 22 '15 at 06:10

3ocene

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score 1 · Answer 4 · answered Dec 22 '15 at 06:10

Well I think you need to use

 if(bad_input.equals("x")){
       loop = false;
       return;
  }

== checks for same reference

.equals checks for same values

http://www.programmerinterview.com/index.php/java-questions/java-whats-the-difference-between-equals-and/

score 1 · Answer 5 · answered Dec 22 '15 at 06:38

May be you should use equalsIgnoreCase method.

if (bad_input.equalsIgnoreCase("x")) {

And to exit the loop at any value other then integer, you can simply use break.

catch (InputMismatchException ex) {
                // here if input != INTEGER

                String bad_input = input.next();
                System.out.println("Bad Input: " + bad_input);

                break;
            }

How to manually exit a while loop (java)

5 Answers5