core java. isInteger methods. Finding bug.

public static int isInputInteger(){
		@SuppressWarnings("resource")
		Scanner input = new Scanner(System.in);   

		int correctNumber;
		
			while(true){   
			input.nextLine();
				    if(input.hasNextInt()){   
				    	correctNumber = input.nextInt();
				        break;
				    }
				    else{
				    	System.out.println("Your input isn't integer.Please, try again. ");
				    }
			}
			return correctNumber;
			}

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class PrintFromInput {

	protected static int  printNumber() {
    	System.out.printf("Please, enter integer: ");
    	int intYourConsoleInput = Assert.isInputInteger();
         return intYourConsoleInput; 
    }
}

public class Task {
    public static void main(String[] args) {
    	
    	System.out.println("Congratulation! Your correct integer input is: "+ PrintFromInput.printNumber()); 
    	
    }
}

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Inside class Assert there is a method "isInputInteger" everything work but not as I expect :
Session 1
input : f
output: {nothing }
input : f
output : Your input isn't integer.Please, try again.
input: g
output : Your input isn't integer.Please, try again.
input : 3
Congratulation! Your correct integer input is: 3
Session OVER
My question is why there isn't any message after first "f". Please, help me to find bug. Thx in advance !

while (true){ System.out.println("Input a number"); if(!(scanner.hasNextInt())){System.out.println("Your input isn't integer.Please, try again. ");scanner.next();continue;} correctNumber = scanner.nextInt(); }

public static int onlyIntegerInput(){ @SuppressWarnings("resource") Scanner scanner = new Scanner(System.in); int correctNumber; while (true){ if(!(scanner.hasNextInt())){ System.out.println("Your input isn't integer. Please, try again. "); scanner.next(); continue; } else{ correctNumber = scanner.nextInt(); break; } } return correctNumber; }

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LVL 17

krakatoaCommented: 2016-08-04

At first glance, maybe because you are advancing the scanner too early.

LVL 16

gurpsbassiCommented: 2016-08-04

why don'y you try setting breakpoints and debugging to find out what going on?

Remove this line :

input.nextLine();

LVL 9

James BilousSoftware EngineerCommented: 2016-08-04

I believe OP needs the nextLine() read in order to advance the scanner past the '\n' character after the integer is read. I would simply move it to the end of the while loop instead of at the beginning.

Yes, indeed. I thought the OP would be able to work out the required code move once he sees the result of just deleting it.

LVL 87

CEHJCommented: 2016-08-04

That code is wrong in so many ways that it's hard to know where to begin. Let's begin with the first line:

a. your code has the name of a boolean method yet it returns int. Why?
b. in the event of your replying that you misnamed the method then why do you skip a line of input (which could have contained an int)?

I think if you just want to get your loop working, you can go along these lines:

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SunnyXAuthor Commented: 2016-08-05

The solution is :

Dear experts thx you so much for your help !

Everybody many thanks !

krakatoaCommented: 2016-08-05

Yes, that's it.

core java. isInteger methods. Finding bug.

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