java do while missing return statement

Question

I have a method, it hints that the return statement is missing, but I don’t think the statement return -1 will be executed. Can anybody tell me why?

private int loop() {
    int retryTimes = 2;
    do {
        try {
            // simulate real business
            int value = new Random().nextInt(3);
            if (value % 3 != 0) {
                throw new RuntimeException();
            }
            return value;
        } catch (Exception e) {
            if (retryTimes <= 0) {
                throw e;
            }
        }
    } while (retryTimes-- > 0);
    // if below line not exists; prompt error: missing return statement
    return -1;
}

It's just because the compiler is not able to detect that it will never reach this line — Zinc
– Zinc, Commented Dec 11, 2020 at 5:42

Tim Biegeleisen · Accepted Answer · 2020-12-11 05:43:39Z

1

The Java compiler suspects that should the while loop iterate more than 2 times, that line with the return -1 would be reached. And, should there not a be a return statement there, then it would be a problem.

That your actual code's logic doesn't necessarily allow for this doesn't matter to the compiler. There can always be unexpected exceptions, so you should rightfully have a catch-all return statement at the end of the method, outside the loop.

answered Dec 11, 2020 at 5:43

Tim Biegeleisen

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Comments

Richard Ochom · Accepted Answer · 2020-12-11 05:58:09Z

0

You can put the return statement inside the catch block like this since you are returning a value on the successful execution, you also need to return a value on failure.

     private int loop() {
        int retryTimes = 2;
        do {
            try {
                // simulate real business
                int value = new Random().nextInt(3);
                if (value % 3 != 0) {
                    throw new RuntimeException();
                }
                return value;
            } catch (Exception e) {
                if (retryTimes <= 0) {
                    throw e;
                }
                return -1;
            }
        } while (retryTimes-- > 0);
    }

answered Dec 11, 2020 at 5:58

Richard Ochom

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