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Learn how to fix looping problems in your Java program when using Scanner for user input with try-catch blocks and error handling.
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This video is based on the question https://stackoverflow.com/q/64408546/ asked by the user 'Meto ballaes' ( https://stackoverflow.com/u/11268640/ ) and on the answer https://stackoverflow.com/a/64408633/ provided by the user 'aziz k'h' ( https://stackoverflow.com/u/12967894/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Solving the Java Scanner Looping Issue with Try-Catch Blocks

When developing Java programs, you might encounter scenarios where you need to gather user input. A common problem arises when a user provides incorrect input, such as entering text when a number is expected. In this guide, we'll tackle a specific issue where a Java program continuously loops due to improper error handling when asking for the player's age.

Understanding the Problem

In our Java program, we are attempting to read the age of a player, but if the user enters a string instead of a number, the program doesn't handle the error properly and gets stuck in a loop. The prompt “Age of the player?” keeps reappearing, and the program fails to recover from the invalid input.

To illustrate the issue, consider the following code snippet where we try to read the player's age:

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

Why the Code Gets Stuck

The logic behind this code causes it to enter an infinite loop under certain conditions:

The in.hasNextInt() method checks for an integer input but might not be called, leading to no action during the ‘else’ block.

The catch block captures any exceptions stemming from invalid input (like a string) but doesn’t prompt for new input again.

The Solution

To resolve this issue, we can make some improvements to the code structure. The key changes will enable the program to handle user input more effectively and ensure that it can break out of the loop when valid input is received.

Revised Code Implementation

Here’s how we can rewrite the code:

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

Breakdown of Changes

Input as String: We first read the input as a string. This step is crucial because it allows us to catch any exceptions from invalid number formats effectively.

Integer Conversion: We use Integer.parseInt(s) to convert the string to an integer. If the string isn’t a valid number, it throws a NumberFormatException, which we can catch.

Check for Valid Age: After successfully converting the input to an integer, we check if the age falls within a valid range (between 6 and 100).

Informative Error Messages: Instead of using checkError(4), which might not be clear to users, we provide a descriptive prompt about the error, improving user experience.

Conclusion

By implementing these changes, we effectively handle user inputs and ensure that the program behaves correctly when faced with invalid data. The revised approach not only resolves the looping issue but also enhances the overall robustness of the Java program.

Feel free to experiment with this techniques to better manage user input in your Java applications, improving both functionality and user experience!