18_exception_handling.dart

// OBJECTIVE: Exception Handling
// 1. ON Clause
// 2. Catch Clause with Exception Object
// 3. Catch Clause with Exception Object and StackTrace Object
// 4. Finally Clause
// 5. Create our own Custom Exception

void main() {

	print("CASE 1");
	// CASE 1: When you know the exception to be thrown, use ON Clause
	try {
		int result = 12 ~/ 0;
		print("The result is $result");
	} on IntegerDivisionByZeroException {
		print("Cannot divide by Zero");
	}

	print(""); print("CASE 2");
	// CASE 2: When you do not know the exception use CATCH Clause
	try {
		int result = 12 ~/ 0;
		print("The result is $result");
	} catch (e) {
		print("The exception thrown is $e");
	}

	print(""); print("CASE 3");
	// CASE 3: Using STACK TRACE to know the events occurred before Exception was thrown
	try {
		int result = 12 ~/ 0;
		print("The result is $result");
	} catch (e, s) {
		print("The exception thrown is $e");
		print("STACK TRACE \n $s");
	}

	print(""); print("CASE 4");
	// CASE 4: Whether there is an Exception or not, FINALLY Clause is always Executed
	try {
		int result = 12 ~/ 3;
		print("The result is $result");
	} catch (e) {
		print("The exception thrown is $e");
	} finally {
		print("This is FINALLY Clause and is always executed.");
	}

	print(""); print("CASE 5");
	// CASE 5: Custom Exception
	try {
		depositMoney(-200);
	} catch (e) {
		print(e.errorMessage());
	} finally {
		// Code
	}
}

class DepositException implements Exception {
	String errorMessage() {
		return "You cannot enter amount less than 0";
	}
}

void depositMoney(int amount) {
	if (amount < 0) {
		throw new DepositException();
	}
}