should I use Exception to simulate a goto statement in java

Question

I've learned that Exception is slow:

but this article(http://blogs.atlassian.com/2011/05/if_you_use_exceptions_for_path_control_dont_fill_in_the_stac/) says that we can use Exception to simulate a goto statement:

so I think it's ok to write my code like this:

public class MyService {

    public Result service(int i) {
        Result result = new Result();
        try {

            Util.checkCommonArguments(i);

            //my business logic...
            if ((i % 2) != 0) {
                throw new BizException("002", "can not be odd");
            }
            if (i > 200) {
                throw new BizException("003", "can not be greater than 200");
            }

            // the normal processing...


            result.setCode("000");
            result.setDesc("ok");
        } catch (BizException e) {
            result.setCode(e.getCode());
            result.setDesc(e.getMessage());
        } catch (Exception e) {
            result.setCode("999");
            result.setDesc("system error");
        }
        return result;
    }


}

class Util {
    public static void checkCommonArguments(int input) {
        if (input < 0) {
            throw new BizException("001", "can not be negative.");
        }
        //maybe more
    }
}

class Result {

    private String code;
    private String desc;

    //getter and setter
}

class BizException extends RuntimeException {
    private String code;

    public BizException(String code, String message) {
        super(message);
        this.code = code;
    }
    @Override
    public Throwable fillInStackTrace()
    {
        return this;
    }
}

but 'dont fill in the stack trace' does not work:

// throw but catch, but not Filling in exception stack traces 
public void method5(int i) {
    try {
        value = ((value + i) / i) << 1;
        // i & 1 is equally fast to calculate as i & 0xFFFFFFF; it is both
        // an AND operation between two integers. The size of the number plays
        // no role. AND on 32 BIT always ANDs all 32 bits
        if ((i & 0x1) == 1) {
            throw new MyBizException();
        }
    } catch (MyBizException e) {
        //maybe do something
    }
}

method5's cost time is almost the same as:

    // This one will regularly throw one
public void method3(int i) throws Exception {
    value = ((value + i) / i) << 1;
    // i & 1 is equally fast to calculate as i & 0xFFFFFFF; it is both
    // an AND operation between two integers. The size of the number plays
    // no role. AND on 32 BIT always ANDs all 32 bits
    if ((i & 0x1) == 1) {
        throw new Exception();
    }
}

Now I'm confused. On one side, I want my code clean and clear(like the class 'MyService'). On the other side, Exception is really slow.

Should I use Exception to simulate a goto statement? Thanks.

It's not a bad approach, actually quite common. Two things to comment on: *You don't simulate gotos*, those BASIC days are over. But of course you change the flow of execution. *You can only handle one exception at a time* - which might or might not be appropriate for your validation. Another common pattern would be to add to some sort of validation error list... — Jan Groth, Mar 31 '15 at 01:00

score 4 · Answer 1 · answered Mar 31 '15 at 01:04

4

Don't use exceptions for normal program flow. They are for exceptional circumstances beyond the developer's control. They are slow, inefficient, and designed for error handling, not business logic.

Stimulating a goto is a bad design decision in today's development environment anyways. They are confusing to follow, and difficult to maintain. Refactor your code to use breaks or other control logic instead.

answered Mar 31 '15 at 01:04

Tim

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Not sold on the "*exceptional circumstances*" part. You don't manually validate a `String` before you convert it to an `Integer` just to avoid a "*slow and inefficient*" `NumberFormatException`, do you? ;) – Jan Groth Mar 31 '15 at 01:28
@jangroth No, but that's because there is no alternative. It would have been better if `Integer.valueOf(string)` returned `null` rather than throwing a `NumberFormatException`. – Paul Boddington Mar 31 '15 at 02:19
In many languages I would actually. In .Net I would tryparse, in others I would check it natively there. As mentioned when you don't have a good choice, you go with it. But regardless, if I expect a string to be numeric when passed to me, then the fact it isn't is actually exceptional. Expected number, got something else. If I was writing a contact for that call I would put in there that I expected a string representation of a number. – Tim Mar 31 '15 at 03:21

score 0 · Answer 2 · answered Mar 31 '15 at 01:28

Using exception for flow control is neither in the interest of good design nor efficient. At the very minimum this will create unnecessary objects. I would encourage you to have a look at Joshua Bloch's "Effective Java" which explicitly covers this topic.

should I use Exception to simulate a goto statement in java

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