How to Prevent Infinite Loops When Handling InputMismatchException in Java?

Infinite Loop in try/catch Block with InputMismatchException: A Solution

Your Java program encounters an infinite loop when handling an InputMismatchException in a try/catch block while taking integer input from the user. This behavior stems from the fact that after catching the InputMismatchException, the scanner remains in an invalid state, leading to the repetition of the loop indefinitely.

To resolve this issue, you must perform the following operations within the catch block:

catch (InputMismatchException e) {
    System.out.println("Error!");
    input.next(); // Move to the next line to avoid the infinite loop
}

The input.next() method advances the scanner pointer to the next line, effectively discarding any invalid input that caused the exception.

Alternatively, you can utilize the hasNextInt() method before attempting to read an integer, thereby ensuring that the value being read is indeed an integer. This approach eliminates the need for exception handling altogether:

while (true) {
    if (input.hasNextInt()) {
        n1 = input.nextInt();
        break;
    } else {
        input.next(); // Skip non-numeric input
    }
}

Remember, the Java Scanner documentation states that after an InputMismatchException is thrown, the scanner will not pass the token responsible for the exception, requiring it to be retrieved or bypassed through other means. Implementing these modifications should mitigate the infinite loop issue in your Java program.

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