Скачать или смотреть Understanding and Fixing the java.util.InputMismatchException in Java Scanner Input

Learn how to troubleshoot the `java.util.InputMismatchException` in your Java programs, specifically when using the Scanner for user input. This guide explains common causes and presents clear, actionable solutions.
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This video is based on the question https://stackoverflow.com/q/64854034/ asked by the user 'holdthemayo7' ( https://stackoverflow.com/u/14646317/ ) and on the answer https://stackoverflow.com/a/64854174/ provided by the user 'Shubham Chopra' ( https://stackoverflow.com/u/9129885/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Troubleshooting the java.util.InputMismatchException in Java

When working on a Java program that involves user input, you might encounter the dreaded java.util.InputMismatchException. This exception can halt your application abruptly and leave you puzzled about what went wrong. In this guide, we'll explore a common scenario that triggers this exception and, more importantly, how to resolve it effectively.

The Problem: InputMismatchException

You might be trying to take user inputs one at a time using Java's Scanner. However, when you run your code, you encounter an exception like so:

[[See Video to Reveal this Text or Code Snippet]]

In this specific case, the issue arises from the way the program is structured to accept inputs from the user. Let's take a look at the relevant portion of your code snippet where you tried to implement this logic:

[[See Video to Reveal this Text or Code Snippet]]

Here lies the problem—chng = scnr.nextInt(); is not nested within the if-statement. Thus, no matter what the user's input is, the program continues to expect an integer input, leading to the InputMismatchException if the command isn't appropriate.

Understanding the Cause

The essence of the issue is the structure of the input handling in your code. When a user inputs 'q' to quit the loop, the program still tries to read an integer with nextInt(), which results in the InputMismatchException because 'q' is not a valid integer.

Key Points to Remember

Placement of Input Reading: Always make sure that you’re asking for new input only when the relevant condition is triggered.

Data Type Consistency: Ensure that the input types match what is expected. If you're reading an integer, ensure the input provided is indeed numeric.

The Solution

To fix this issue, you need to adjust the positioning of chng = scnr.nextInt(); to only execute when the user has chosen the option 'u'. Here's the corrected code:

[[See Video to Reveal this Text or Code Snippet]]

Updated Code Snippet

The complete segment of your code will look something like this after the modification:

[[See Video to Reveal this Text or Code Snippet]]

Testing the Fix

After implementing this fix, you can run your program again. Try entering the different inputs as before. You should now be able to exit the loop with 'q' without receiving any exceptions.

Conclusion

Learning to handle user input correctly in Java can save you from many headaches down the line. By ensuring that your input requests are contextual and that you're handling exceptions gracefully, you'll create a more robust application. Whenever you face InputMismatchException, take a moment to review your input logic—there might be a simple fix waiting to be discovered!

This solution should empower you to handle inputs effectively and ride through your Java programming journey with more confidence.