asked on

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 !

krakatoa

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

gurpsbassi

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

krakatoa

Remove this line :

input.nextLine();

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SOLUTION

James Bilous

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krakatoa

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.

SOLUTION

CEHJ

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ASKER CERTIFIED SOLUTION

krakatoa

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SunnyX

ASKER

The solution is :

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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Dear experts thx you so much for your help !

SunnyX

ASKER

Everybody many thanks !

krakatoa

Yes, that's it.