How to solve “NumberFormatException”


What is NumberFormatException?
NumberFormatException is an exception that occurs in programming when a string is attempted to be converted into a numerical value (such as an integer or a floating-point number), but the string does not have a valid numeric format. This exception is commonly encountered when using programming languages that provide functions or methods for converting strings to numbers, such as Java or C++.

Reasons for NumberFormatException:

1.    Invalid characters: The string contains characters that are not valid for a numeric value. For example, if you try to convert the string "123a" into an integer, it will result in a NumberFormatException because the character 'a' is not a valid digit.

Solution: Before converting a string to a number, you can validate the input using regular expressions or built-in functions to ensure that it only contains valid numeric characters. Alternatively, you can catch the NumberFormatException and handle it gracefully in your code.

Example:

String str = "123a";

try {

    int num = Integer.parseInt(str);

    System.out.println("Number: " + num);

} catch (NumberFormatException e) {

    System.out.println("Invalid input: " + str);

}


2.    Empty or null string: The string is empty or null, and therefore cannot be converted to a numeric value. For example, if you try to convert an empty string "" or a null reference into a number, it will result in a NumberFormatException.

Solution: You should check if the string is empty or null before attempting to convert it to a number. Handle these cases separately to avoid the exception. You can either provide a default value or throw a custom exception to indicate the invalid input.

Example:

String str = "";

if (str != null && !str.isEmpty()) {

    int num = Integer.parseInt(str);

    System.out.println("Number: " + num);

} else {

    System.out.println("Invalid input: " + str);

}

 

3.    Number format mismatch: The string has a valid format but does not match the expected format for the conversion. For example, if you try to convert the string "12.34" into an integer using Integer.parseInt(), it will result in a NumberFormatException because integers do not allow decimal places.

Solution: Ensure that the string format matches the expected format for the conversion. If you need to convert decimal numbers, use appropriate parsing methods or classes designed for floating-point numbers, such as Double.parseDouble() or Float.parseFloat().

Example:

String str = "12.34";

try {

    int num = Integer.parseInt(str);

    System.out.println("Number: " + num);

} catch (NumberFormatException e) {

    System.out.println("Invalid format: " + str);

}


By addressing these reasons and applying the appropriate solutions, you can handle NumberFormatExceptions effectively and prevent unexpected errors in your code when converting strings to numeric values.