How to make a math.random into a for loop

Question

in short form, i created a math.random that will choose a random number, then another variable later will use that number. After that random is used math.random will choose another number, and this would go on forever. I would think to use a for loop with the math.random making it look something like this:

for (int i = 0; i <100; i++) {
    int mRandom = (int) (Math.random() * 21 + 15);
}

then later I use the number to change the speed and angle of the sprite i created (this entire code is used to create the sprite so I don't have a problem with the sprite being used)

   for (int i = mIDontKnowTimer; i == mRandom; i++) {

here I have a timer that i already created, and when that timer is equal to the number generated by mrandom the speed and angle changes

        int pSpeed = (int) (Math.random() * 3 + 3);
        int pAngle = (int) (Math.random() * 359);

        mXSpeed = pSpeed * Math.cos(pAngle);
        mYSpeed = pSpeed * Math.sin(pAngle);
    }

Im confused as to how to make the mRandom a loop, because it is saying the first line has an illegal start of type and that it can't find "i" in the code

Answer 1

I'd first put Math.Random into a function and call it in my main loop.

public static int randomNumberGenerator(int min, int max){
        Random rand = new Random();
        return rand.nextInt(max - min) +min;

    }

Now call it within a for/while loop.

Answer 2

As written , your mRandom is only valid within the scope of the first for loop, and will be completely unavailable to your second for loop. (I say "as written" because I suspect your code doesn't actually look like this - it would fail to compile.)

Your second loop isn't particularly clear to me, but it looks like you're trying to change your sprite's direction and speed mRandom times? (Edit: comments confirm this.)

You could just use a nested for loop to accomplish this:

int mRandom;
int pSpeed, pAngle;

for (int i = 0; i <100; i++) { //100 times in a row,
    mRandom = (int) (Math.random() * 21 + 15); //generate a random number

    for (int j = 0; j < mRandom; j++) { //count up to that random number
        //and repeatedly adjust your sprite's properties
        pSpeed = (int) (Math.random() * 3 + 3);
        pAngle = (int) (Math.random() * 359);

        mXSpeed = pSpeed * Math.cos(pAngle);
        mYSpeed = pSpeed * Math.sin(pAngle);
    }
}

It's worth noting that, unless you're redrawing your sprite somewhere in there, the extra speed and angle changes will be meaningless - you're updating those properties multiple times but only redrawing once, so only the most recent change will stick.

Answer 3

I think you're trying to do this

for (int i = 0; i <100; i++) {
    int mRandom = (int) (Math.random() * 21 + 15);

    for (int i = mIDontKnowTimer; i == mRandom; i++) {
        ....
    }
}

The issue you are seeing is that you were trying to access the mRandom variable outside of it's scope.