What is the purpose of validation in Java?

In Java, validation is used to verify if the input data meets the expected rules and requirements. It ensures the validity, completeness, and legality of the input data to avoid errors or exceptions in the program.

By using validation, you can ensure that data meets the required formats, ranges, lengths, and types, thus detecting and handling input errors in a timely manner to enhance the robustness and security of the program.

Specifically, the role of validation includes but is not limited to the following aspects:

1. Verify the format and type of data, such as checking if a phone number follows the rules or if an email address is valid.
2. Verify the range and values of the data, such as checking if the age is within a reasonable range or if the amount is greater than 0.
3. Check the length and size of data, for example, verify if a string exceeds the limit or if a file size is reasonable.
4. Ensure that the input data does not contain malicious code or special characters to prevent security vulnerabilities such as SQL injection, cross-site scripting attacks, and more.
5. Provide friendly error messages and feedback so that users can promptly identify and correct input errors, improving the overall user experience.

By utilizing validation, one can effectively ensure the quality and accuracy of program input data, reduce the likelihood of errors, and enhance the reliability and stability of the program.