How to avoid code duplication?

Question

Is it possible to avoid code duplication in such cases? (Java code)

void f()
{
    int r;
    boolean condition = true;
    while(condition)
    {
        // some code here (1)

        r = check();
        if(r == 0)
            break ;
        else if(r == 1)
            return ;
        else if(r == 2)
            continue ;
        else if(r == 3)
            condition = false;

        // some code here (2)

        r = check();
        if(r == 0)
            break ;
        else if(r == 1)
            return ;
        else if(r == 2)
            continue ;
        else if(r == 3)
            condition = false;

        // some code here (3)
    }
    // some code here (4)
}

int check()
{
    // check a condition and return something
}

A possible solution may be using Exceptions, but that doesn't seem to be a good practice. Is there any so-called good pattern of program flow control in such cases? For example, a way to call break ; from inside the check() function. (Possibly in other programming languages)

Answer 1

Some good answers (especially @Garrett's just now) to a tough question but I'll add my $0.02 for posterity.

There is no easy answer here about how to refactor this block without seeing the actual code but my reaction to it is that it needs to be redesigned.

For example, a way to call break ; from inside the check() function. (Possibly in other programming languages)

If you are asking for a different break that Java does not support (without a hack) and having the duplicated check() and various different loop exit/repeat code indicates to me that this is a large and complicated method. Here are some ideas for you to think about:

• Each of the some code here blocks are doing something. If you pull those out to their own methods, how does that change the loop?

• Maybe break the loop down into a series of comments. Don't get deep into the code but think about it conceptually to see if a different configuration drops out.

• Have you had another developer in your organization who is not involved with this code take a look at it? If you explain in detail how the code works someone they may see some patterns that you are not since you are in the weeds.

I also think that @aix's idea of a finite state machine is a good one but I've needed to use this sort of mechanism very few times in my programming journeys -- mostly during pattern recognition. I suspect that a redesign of the code with smaller code blocks pulled into methods will be enough to improve the code.

If you do want to implement the state machine here are some more details. You could have a loop that was only running a single switch statement that called methods. Each method would return the next value for the switch. This doesn't match your code completely but something like:

int state = 0;
WHILE: while(true) {
    switch (state) {
       case 0:
            // 1st some code here
            state = 1;
            break;
       case 1:
            state = check();
            break;
       case 2:
            return;
       case 3:
            break WHILE;
       case 4:
            // 2nd some code
            state = 1;
            break;
        ...
    }
 }

Hope some of this helps and best of luck.