Non duplicates numbers in user input

Question

I am trying to work out how to create an input validation where it won\'t let you enter the same number twice as well as being inside a range of numbers and that nothing can be

Answer 1

I would rewrite the method recursively to avoid multiple loops.

If you are not familiar with recursively methods it is basically a method that calls itself inside the method. By using clever parameters you can use a recursively method as a loop. For example

void loop(int index) {

   if(index == 10) {
       return;   //End loop
   } 
   System.out.println(index);
   loop(index++);
}

by calling loop(1) the numbers 1 to 9 will be printed.

In your case the recursively method could look something like

public void choose(int nbrOfchoices, List taken) {
      if(nbrOfChoices < 0) {
          return; //Terminate the recursively loop
      }

      System.out.println("Enter enter a number between 1 and 59");

      try {      
          int temp = keyboard.nextInt(); //Scanner.nextInt throws InputMismatchException if the next token does not matches the Integer regular expression
      } catch(InputMismatchException e) {
          System.out.println("You need to enter an integer");
          choose(nbrOfChoices, taken);
          return;
      }
      if (value < 1 || value >= 59) { //Number not in interval
            System.out.println("The number " + temp + " is not between 1 and 59.");
            choose(nbrOfChoices, taken);
            return;
        }

        if (taken.contains(temp)) { //Number already taken
            System.out.println("The number " + temp + " has already been entered.");
            choose(nbrOfChoices, taken);
            return;
        }
        taken.add(temp);
        choose(nbrOfChoices--, taken);
}

Now you start the recursively method by calling choose(yourNumberOfchoices, yourArrayList taken). You can also easily add two additonal parameters if you want to be able to change your number interval.