How to Avoid `NumberFormatException` When Using `parseInt` with Empty Strings in Java?

What are the best practices to prevent `NumberFormatException` from `parseInt` when the input string is empty?

String input = "";
int result = (input == null || input.trim().isEmpty()) ? 0 : Integer.parseInt(input);

The `parseInt` method in Java can throw a `NumberFormatException` if it is given an empty string or a string that does not represent a valid integer. To avoid this exception, it is essential to validate the input before attempting to parse it.

String input = "";
try {
    int result = (input == null || input.trim().isEmpty()) ? 0 : Integer.parseInt(input);
} catch (NumberFormatException e) {
    System.out.println("Invalid number format: " + e.getMessage());
}

Causes

• Input string is empty.
• Input string contains non-numeric characters.
• Input string represents a number too large or small for an integer type.

Solutions

• Check if the input string is null or empty before calling `parseInt`.
• Use exception handling to catch `NumberFormatException` and manage it gracefully.
• Consider using `Optional<Integer>` to handle potential absence of a valid integer.

Mistake: Not checking for null or empty strings before parsing.

Solution: Always validate input using `input == null || input.trim().isEmpty()`.

Mistake: Assuming any string containing digits is a valid integer.

Solution: Implement a regex check to ensure the entire string is a valid integer.

Mistake: Ignoring the potential size of the integer being parsed.

Solution: Use `Long.parseLong` if the input string might exceed the integer range.