Scanner input not working when used in a While loop

Question

I'm trying to create a method to validate a user input to be "1". Therefore I used a while loop for validation. Yet, it enters the while loop when the input is "1".

public static int switchInput() {

    System.out.print("\n" + "Enter your selection: ");

    Scanner userInput = new Scanner(System.in);
    String selection = userInput.next();

    while (selection != "1" /*&& selection != "2" && selection != "3"*/){

        System.out.println("Enter 1: ");
        //System.out.println("Please enter either '1','2' or '3': ");
        selection = userInput.next();

    }

    int result = Integer.parseInt(selection);
    return result;
}

Output:

What would you like?
1: Regular Hamburger
2: Healthy Burger
3: Deluxe Burger

Enter your selection: 
1
Enter 1: 
1
Enter 1: 
1
Enter 1: 

Process finished with exit code -1

!selection.equals("1") use this instead of selection != "1". — Rax, Dec 29 '18 at 08:44
Possible duplicate of [How do I compare strings in Java?](https://stackoverflow.com/questions/513832/how-do-i-compare-strings-in-java) — MC Emperor, Dec 29 '18 at 09:22

Kunal Puri · Accepted Answer · 2018-12-29T09:11:20.190

1

selection != "1" is wrong. != checks for reference inequality i.e. if the objects on both sides are not same, then the condition will return true.

In your case, selection and String object with value 1 are different objects, that's why the condition is returning true.

Instead, use !selection.equals("1")

Edit:

As suggested by Igor Nikolaev, if there is no compulsion of using String object as a choice, you could use int selection = userInput.nextInt() for getting selection as int. In that case, you can use selection == 1.

edited Dec 29 '18 at 09:11

answered Dec 29 '18 at 08:41

Kunal Puri

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Alternatively it's possible to use `int selection = userInput.nextInt()` since you expect user to enter a number and you still parse the string into number afterwards. – Igor Nikolaev Dec 29 '18 at 08:57
Thanks for your suggestion, @IgorNikolaev. I have included your point in the answer. – Kunal Puri Dec 29 '18 at 09:11
Works like a charm. Thanks – Lord Heffe Jan 23 '19 at 12:28

score 0 · Answer 2 · answered Dec 29 '18 at 09:14

You see, the variable 'selection' is a string, and to compare two string using != is incorrect. Instead, use the method equals() So I see you want to compare the String selection and a string "1" replace the if condition with:

while(!selection.equals("1")){

TIP: You expect the user to input a number, so why make selection a string? It would be better if it was an int.

Scanner input not working when used in a While loop

2 Answers2