InputMismatchException in LOOP

Question

I tried to find a solution for my problem, but couldn't find one that worked in practice. So please, if YOU'RE NOT SURE you know what the solution is, don't answer. I really need concrete help.

The problem is that when I run my simple code - you can pick a number and it's ok, loop is working fine. When you pick 0, it works too (run is finished), but when you put a letter or any string - there's a problem... an exception keeps looping without stop, even if I try inputting another value.

PS. I need to use Scanner here so please don`t write about readers etc. - just how to solve this specific problem.

Cheers,

Here's code (only main):

public static void main(String[] args) {
    // TODO code application logic here
    Scanner sc = new Scanner(System.in);
    int dane = -1 ;

     boolean keepLooping;   //if you delete this works the same with same problem
do  
{    
    keepLooping = false;
    try
    {

            System.out.println("Pick a number:");
            dane = sc.nextInt();


    }catch (InputMismatchException e)
      {
          System.out.println("Your exception is: " + e);
          keepLooping = false;
      }  
    System.out.println("Out from exception");

}while ((dane != 0)||(keepLooping == true));   

}

Answer 1

Try this:

public static void main(String[] args) {
    // TODO code application logic here
    Scanner sc = new Scanner(System.in);
    int dane = -1 ;

     boolean keepLooping = true;   //if you delete this works the same with same problem
while(keepLooping && dane != 0)  
{    

    System.out.println("Pick a number:");
try
{ 

        dane = Integer.parseInt(sc.next());


}catch (NumberFormatException e)
  {
       keepLooping = true;
  }  
System.out.println("Out from exception");

}

Answer 2

Problem is when you say -

dane = sc.nextInt();

in the above line if you give an input of anything else than a number it will throw an exception input mismatch. Lets understand what this line does. actually two things -

first sc.nextInt() reads an integer and only on successfull completion of this task it will assign that integer value to variable dane. but while reading an integer it throws an InputMismatchException so the assignment never happened and yet dane has it's previos value not the new one which scanner read so dane is still not equals to 0. so the loop continues.

I hope it helps.

Answer 3

Edited

Do like this

public static void main(String[] args) {
        // TODO code application logic here
        Scanner sc = new Scanner(System.in);
        int dane = -1 ;

         boolean keepLooping;   //if you delete this works the same with same problem
    do  
    {    
        keepLooping = false;
        try
        {

                System.out.println("Pick a number:");
                dane = sc.nextInt();


        }catch (InputMismatchException e)
          {
              System.out.println("Your exception is: " + e);
              keepLooping = false;
              dane = sc.nextInt();
          }  
        System.out.println("Out from exception");

    }while ((dane != 0)||(keepLooping == true)&&(dane!=0));   

    }