CODEWITHSUNDEEP
java
james Fog
james Fog

Reputation: 71

Why is this java input validation loop not working

   import java.util.Scanner;

   //this program test input validation yes or no program

public class Fool
 {
   public static void main(String [] args)
   {
    String input;
    char first;
    Scanner keyboard=new Scanner(System.in);

    System.out.println("Enter yes or no ");
         input=keyboard.nextLine();
        first=input.charAt(0);
        System.out.print(first);
         while( first !='y' || first !='n')
          {
        System.out.println("please enter yes or no");
          }

       }
   }

What is trying to get the program to is that the user has to remain in the while loop if the user does not put in yes or no.

Upvotes: 2

Views: 556

Answers (4)

Hello World
Hello World

Reputation: 395

You should change your code to

boolean b=false;
while(b==false){
    if(first !='y' || first !='n'){
        System.out.println("please enter yes or no");
    } else {
        b=true;
    }
}

Upvotes: 1

Jinendra
Jinendra

Reputation: 72

while( first !='y' || first !='n') is always true. As OR operation works as follows

condition 1 condition 2 result

TRUE TRUE TRUE

TRUE FALSE TRUE

FALSE TRUE TRUE

FALSE FALSE FALSE

In your case one condition will be always true, therefore it enters in while loop everytime While AND operation works as follows

condition 1 condition 2 result

TRUE TRUE TRUE

TRUE FALSE FALSE

FALSE TRUE FALSE

FALSE FALSE FALSE

so instead of using OR try using AND e.g. while( first !='y' && first !='n')

Upvotes: 1

user3575886
user3575886

Reputation: 

while( first !='y' || first !='n') is always true.

Replace your code with:

while( first !='y' && first !='n')

Upvotes: 1

Madhawa Priyashantha
Madhawa Priyashantha

Reputation: 9872

change this to 

while( first !='y' || first !='n') {
        System.out.println("please enter yes or no");
}

this 

while( first !='y' && first !='n') {
        System.out.println("please enter yes or no");
}

because (first !='y' || first !='n') is always true.

if first =='y' then first !='n' is true

if first =='n' then first !='y' is true.

so while condition is always true what you need is not || but && [and ]

Upvotes: 2

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