Importance of error handling

Error handling is the part of a program that detects errors and exceptional situations at run time and responds to them in a controlled way (recover, retry, report or terminate safely), instead of letting the program crash or produce wrong results. In OO languages it is done with exceptions (try, catch, finally, throw).

Importance (major functions)

1. Reliability and robustness - the system continues to work or fails safely when something goes wrong (invalid input, file missing, network failure, divide by zero, database down).
2. Separation of normal logic from error logic - the main code remains clean; the error code is in catch blocks.
3. Propagation of errors - an exception thrown deep in the call stack is passed up to a method that knows how to handle it, avoiding repeated return-code checks.
4. Protection of data and resources - finally (or try-with-resources) closes files, connections and releases locks, so no leaks or corrupt data.
5. User-friendly messages and recovery - the user gets a meaningful message instead of a system crash; the program can retry or use a default.
6. Debugging and maintenance - logging stack traces helps find faults.
7. Security - avoids leaking internal details and unsafe states.

try {
    int n = Integer.parseInt(input);
    int r = 100 / n;
} catch (NumberFormatException e) {
    System.out.println("Enter a number");
} catch (ArithmeticException e) {
    System.out.println("Cannot divide by zero");
} finally {
    System.out.println("done");   // always runs
}

Is it required to develop a program?

Yes. Even correct code meets conditions it cannot control (user mistakes, hardware, network). A program without error handling may terminate abruptly, lose data or give wrong answers. Therefore error handling must be planned in design and implemented in every serious system; in some languages (e.g. Java checked exceptions) the compiler even forces the programmer to handle them.