java.lang.NumberFormatException: For input string: "2021-07-22T19:15:30"

This exception is thrown when the code tries to convert a string into a number, but the string is not in a valid number format. In this specific case, the string "2021-07-22T19:15:30" cannot be converted into a number because it contains characters that are not numeric. This error can occur in various situations, depending on the code logic and the input data.

For example, if the code is trying to parse a date string into a numeric value, it may need to use a different method or library that can handle date strings. Alternatively, if the code is expecting a numeric input from a user or a file, it may need to validate the input and reject any non-numeric values.

To fix this error, you need to identify the root cause of the problem and modify the code accordingly. The error message should provide some clues about where the error occurred and what data caused it. You can also use debugging tools or print statements to inspect the values of variables and parameters at runtime. Once you have identified the issue, you can update the code to handle the input data correctly and avoid the NumberFormatException.