Multi-catch and rethrow

Definition

A multi-catch handles several exception types in one block, written catch (A | B e). Use it when the handling is the same. You can also rethrow an exception after logging it, so callers still see the failure.

Example code

One handler for two kinds of failure

class Demo {
    static int divide(String a, String b) {
        try {
            return Integer.parseInt(a) / Integer.parseInt(b);
        } catch (NumberFormatException | ArithmeticException e) {   // same handling for both
            System.out.println("Cannot calculate: " + e.getMessage());
            throw e;                                                  // log it, then let the caller know
        }
    }

    public static void main(String[] args) {
        System.out.println(divide("10", "2"));
        for (String[] pair : new String[][] {{"10", "0"}, {"ten", "2"}}) {
            try {
                divide(pair[0], pair[1]);
            } catch (RuntimeException e) {
                System.out.println("caller saw " + e.getClass().getSimpleName());
            }
        }
    }
}

// Output:
// 5
// Cannot calculate: / by zero
// caller saw ArithmeticException
// Cannot calculate: For input string: "ten"
// caller saw NumberFormatException