How would I use a while loop to keep requesting user input

Question

I've tried a couple of things with the while loop and can't seem to get it to work. I want to keep requesting user input until the user inputs the number 0, here is the code I have so far:

import java.util.*;

public class Task10 {

    public static void main(String[] args) {
        System.out.println("Enter a year to check if it is a leap year");
        Scanner input = new Scanner(System.in);
        int year = input.nextInt();

        if ((year % 4 == 0) || ((year % 400 == 0) && (year % 100 != 0)))
            System.out.println(year + " is a leap year");
        else
            System.out.println(year + " is not a leap year");
    }
}

Although not really what you asked, I see that you posted after the release of JDK 8 which included the introduction of the date-time API and therefore you can use [static] method isLeap (of class java.time.Year) rather than do the calculation yourself. — Abra
– Abra, Commented Oct 3, 2023 at 8:34

vish4071 · Accepted Answer · 2015-10-09 10:50:39Z

9

Use a while loop above input line as:

 while(true)

And, use if condition to break.

if(year == 0)
    break;

Also, condition for leap year is wrong in your code. It should be:

if((year % 100 == 0 && year % 400 == 0) || (year % 4 == 0 && year % 100 != 0))
    //its a leap year
else
    //its not

PS: As in comments, I'll give a complete code:

import java.util.*;

public class Task10 {

public static void main(String[] args) {
    System.out.println("Enter a year to check if it is a leap year");
    while(true){
    Scanner input = new Scanner(System.in);
        int year = input.nextInt();
        if(year == 0)
            break;
        if((year % 100 == 0 && year % 400 == 0) || (year % 4 == 0 && year % 100 != 0))
            System.out.println(year + " is a leap year");
        else
            System.out.println(year + " is not a leap year");
    }
}

}

edited Oct 9, 2015 at 10:50

answered Oct 9, 2015 at 10:40

vish4071

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1 Comment

Imminence Over a year ago

Thanks mate, worked a charm. Still getting used to while loops and this explanation sunk in!

Saif Asif · Accepted Answer · 2015-10-09 10:44:48Z

3

You need to do something to keep you input loop running until a stopping condition is encountered (which in your case is that when the user inputs 0)

// First get the scanner object with the input stream
Scanner sc = new Scanner(System.in); 

// Just using do-while here for no reason, you can use a simple while(true) as well
do{
    int input = sc.nextInt();  // read the next input
    if (int == 0) { // check if we need to exit out
        // break only if 0 is entered, this means we don't want to run the loop anymore
        break;
    } else {
        // otherwise, do something with the input
    }
} while(true); // and keep repeating

answered Oct 9, 2015 at 10:44

Saif Asif

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Comments

NightsWatch · Accepted Answer · 2015-10-09 10:43:01Z

0

You should place your input taking code inside a while loop aned execute while loop untill year is 0 or lesser.

public static void main(String[] args) {
        int year = 1;
        while(year > 0)
        {
            System.out.println("Enter a year to check if it is a leap year");
            Scanner input = new Scanner(System.in);
            year = input.nextInt();
            if ((year % 4 == 0) || ((year % 400 == 0) && (year % 100 != 0)))
                System.out.println(year + " is a leap year");
            else
                System.out.println(year + " is not a leap year");
        }


    }

answered Oct 9, 2015 at 10:43

NightsWatch

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4 Comments

vish4071 Over a year ago

Why would you make scope of year variable local of main, when it is never required outside the while loop ?!

NightsWatch Over a year ago

@vish4071 it reduces the number of lines of code needs to be written instead of marking the while as true at first and then checking for condition if year is 0 to break the loop I felt I can make the beginner understand better this way

vish4071 Over a year ago

It is bad practice. You should try and declare / define variables to use only when they are required. Make it rule of the thumb. A few LoC has no effect on project, but, scope of variables and memory etc makes a lot of difference.

vish4071 Over a year ago

But since it is a small program, it does not matter much :)

Deep Narayan Kumar · Accepted Answer · 2023-10-02 14:33:18Z

-1

Simple and best

Scanner sc=new Scanner(System.in);

while(sc.hasNextInt()){ int year = input.nextInt();

    if ((year % 4 == 0) || ((year % 400 == 0) && (year % 100 !=0)))
        System.out.println(year + " is a leap year");
    else
        System.out.println(year + " is not a leap year");

}

Until you enter a valid input , the loop will contionue

edited Oct 2, 2023 at 14:33

answered Sep 30, 2023 at 19:46

Deep Narayan Kumar

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3 Comments

Abra Over a year ago

The single line of code, in your answer, is not formatted and does not compile. I assume that sc is an instance of java.util.Scanner. If that instance was created like so: new Scanner(System.in), then sc.hasNext() will never return false, so how does that answer the original question?

Deep Narayan Kumar Over a year ago

Update for more redable, instance sc created only once, when you enter invalid input loop will be break

Abra Over a year ago

Still haven't learned how to format code using markdown? By the way, the code in your answer still doesn't compile.

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