Why Does My Java Scanner Throw a NoSuchElementException, and How Can I Fix It?

NoSuchElementException Frustrations with Java.Util.Scanner

Encountering a "NoSuchElementException" error can be perplexing, especially for Java novices like yourself. This error occurs when the Scanner class cannot retrieve the next token from the input stream. Let's delve into your specific code to uncover the root cause:

import java.util.Scanner;

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

    int number1; // first number to add
    int number2; // second number to add
    int sum; // sum of 1 & 2

    // Problem: Reading input values without checking for input availability

    System.out.print("Enter First Integer: ");
    number1 = input.nextInt(); // Exception occurs here when no input is provided

    System.out.print("Enter Second Integer: ");
    number2 = input.nextInt(); // Exception occurs here if input is not available for this prompt

    sum = number1 + number2; // Addition occurs, assuming input values are available

    System.out.printf("Sum is %d\n", sum); // Displays the sum, if input is available
  }
}

The problem lies in the code attempting to read input without first verifying if input is available. The input.nextInt() method raises a "NoSuchElementException" if the user does not provide an input or enters something other than an integer.

Solution:

To eliminate this issue, we need to check for input availability before attempting to retrieve it:

if (input.hasNextInt()) {
  number1 = input.nextInt();
} else {
  // Handle the case where no input is provided
}

Explanation:

The hasNextInt() method checks if the next token in the input stream is an integer. If it returns true, the input.nextInt() method can be used to retrieve the integer. Otherwise, the code can handle the situation gracefully, such as setting number1 to 0 or displaying an error message.

By implementing this check, your code will no longer throw a "NoSuchElementException" and will behave as expected, allowing users to input integers and calculate their sum.

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