public class DivideByZero {
    public static void main(String[] args) {
        int a = 10, b = 0;
        try {
            int result = a / b; // throws ArithmeticException when b is 0
            System.out.println("Result: " + result);
        } catch (ArithmeticException e) {
            System.out.println("Error: Cannot divide by zero");
        } finally {
            // Runs whether or not an exception was thrown
            System.out.println("Execution finished");
        }
    }
}

▶ Run Code

Output

Error: Cannot divide by zero
Execution finished

Core Logic

Rather than letting a divide-by-zero crash the program, wrap the risky division in try-catch-finally and handle it gracefully.

How It Works

1The risky division a / b sits inside a try block.
2Integer division by zero throws an ArithmeticException at runtime — unlike floating-point division, there's no 'Infinity' fallback.
3The matching catch (ArithmeticException e) block runs instead of the program crashing, printing an error message.
4The finally block runs afterward regardless of whether an exception was thrown.

With a = 10, b = 0, the program prints "Error: Cannot divide by zero" followed by "Execution finished" from the finally block.

💡

Key Point: finally always executes — whether the try block succeeds, throws, or even returns — which makes it the right place for cleanup code.

Key Concepts

try / catchfinallyArithmeticException

Approach 2: Defensive Check (No Exception)

Java

public class DivideByZeroCheck {
    public static void main(String[] args) {
        int a = 10, b = 0;
        // Check the divisor up front instead of relying on an exception
        if (b == 0) {
            System.out.println("Error: Cannot divide by zero");
        } else {
            System.out.println("Result: " + (a / b));
        }
        System.out.println("Execution finished");
    }
}

▶ Run Code

Output

Error: Cannot divide by zero
Execution finished

Core Logic

Or skip the exception altogether — check whether the divisor is zero before you divide, instead of cleaning up after the fact.

How It Works

1if (b == 0) checks the divisor up front, before any division is attempted.
2If it's zero, the error message is printed directly — the risky a / b expression is never even evaluated.
3Otherwise, the else branch safely performs the division, since b is now known to be non-zero.
4"Execution finished" prints unconditionally afterward, matching the finally block's behavior in the try-catch version.

With b = 0, the check catches it immediately and prints "Error: Cannot divide by zero" without ever throwing an exception.

💡

Key Point: Exceptions are for exceptional, hard-to-predict failures — when a condition like 'is the divisor zero' is cheap to check in advance, validating first is usually clearer and slightly faster than relying on try-catch for routine control flow.

Key Concepts

defensive checkif / elsevalidation vs. exception handling

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