Question

I’m trying to improve a Java project which uses a lot of large case statements. In cases where the case statement is used, it is used to handle an event which has an attribute associated to it. For example:

public void jumpOverWall(int wallID) {
    switch (wallID) {
            case 0:
            case 1213:
            case 2123:
            case 3123:
            case 4123:
    }
}

The numbers are non sequential and all require a different action to be performed – for example saying “You cannot jump over this wall” or moving the character to a set position. There are very few cases in which the case response follows a set pattern. What I mean by this is that the switch statements do not follow a pattern that would allow for code similar to:

public void jumpOverWall(int wallID) {
    someArray[1213] = 10;
    someArray[3123] = 20;

    if (playerJumpingSkill > someArray[wallID]) {
            // Do something
    } else {
            sendPlayerMessage("You cannot do this!");
    }
}

Therefore, I am wondering the best possible way of handling these ‘events’. The whole idea of an ‘event handler’ style system is something that appeals to me but I am stuck as how to implement it (or a better solution to the problem). There are too many ‘events’ (in my opinion) to have a separate class for each one.

Is there a method / design for hooking events? Would this be applicable / work. I’d be looking to a method of easy hooking such as:

hookEvent(1213, new SomeInterface() {
    boolean eventOK() {
        // Do something
        return true;
    }
}

Then these ‘hooks’ would be checked for and called?

Answer 1

Why not have a separate method for each case? That way, it makes your code more readable.

public void jumpOverWall(int wallID)
{
      switch (wallID) 
        {
        case 0:     methodA(wallID); break; // you could of course have a more descriptive name here.
        case 1213:  methodB(wallID); break; 
        case 2123:  methodC(wallID); break;
        case 3123:  methodD(wallID); break;
        case 4123:  methodE(wallID); break;
        }
}