How do I use a variable that is declared inside of a for loop outside the loop?

Question

I'm creating ATARI BREAKOUT, using the acm.graphics library and I'm trying to access a "brick" outside of my for loop to delete it. I can't figure out any other way to create the bricks without the for loop. Help?

GRect brick = new GRect(brickwidth, brickheight);
    for(j = 1; j <= nrows; j++) { 
        for(i = 0; i < bricksperrow; i++) {
            brick.setLocation(i*(brickwidth + brickSep) + 1, brickoffset + j*(brickheight + brickSep));
            if(j == 1 || j == 2) {
                brick.setColor(Color.RED);
                brick.setFilled(true);
            }
            else if(j == 3 || j == 4) {
                brick.setColor(Color.ORANGE);
                brick.setFilled(true);
            }
            else if(j == 5 || j == 6) {
                brick.setColor(Color.YELLOW);
                brick.setFilled(true);
            }
            else if(j == 7 || j == 8) {
                brick.setColor(Color.GREEN);
                brick.setFilled(true);
            }
            else if(j == 9 || j == 10) {
                brick.setColor(Color.CYAN);
                brick.setFilled(true);
            }
            add(brick);
        }
    }

Where do you `add` the `brick` to? Keep a reference of created bricks in a `Collection`, a `List` or `Map`, then simply get them from there to delete them. — Boris the Spider, Jan 01 '16 at 18:40
Incidentally your `if` chain could be easily replace by a `switch` statement. Or you could greatly simplify the `if` conditions if you do not wish to use a `switch`. — Boris the Spider, Jan 01 '16 at 18:44
You can't use a variable declared inside a `for` loop outside the loop, and in any case there is no variable declared inside this `for` loop. Unclear what you're asking. — user207421, Jan 03 '16 at 09:32

8bra1nz · Accepted Answer · 2016-01-03T09:05:29.060

I guess you want to create many bricks in for loop.

You are doing it wrong, per iteration you are just changing a position of one brick. You need to create a new brick per iteration and save its reference into some structure preferably a matrix of [nrows, bricksperrow] dimensions.

Here's how:

GRect[][] bricks = new GRect[nrows][bricksperrow];
for(j = 1; j <= nrows; j++) { 
    for(i = 0; i < bricksperrow; i++) {
        bricks[j - 1][i].setLocation(
                      i*(brickwidth + brickSep) + 1, 
                      brickoffset + j*(brickheight + brickSep));
        if(j == 1 || j == 2) {
            brick.setColor(Color.RED);
            brick.setFilled(true);
        }
        else if(j == 3 || j == 4) {
            brick.setColor(Color.ORANGE);
            brick.setFilled(true);
        }
        else if(j == 5 || j == 6) {
            brick.setColor(Color.YELLOW);
            brick.setFilled(true);
        }
        else if(j == 7 || j == 8) {
            brick.setColor(Color.GREEN);
            brick.setFilled(true);
        }
        else if(j == 9 || j == 10) {
            brick.setColor(Color.CYAN);
            brick.setFilled(true);
        }
        add(bricks[j - 1][i]);
    }
}

This way you can have global matrix of bricks from where you can delete any entry.

But now, the matrix is inside the for loop and I can't access it outside it. — Albert Dong, Jan 03 '16 at 01:32
It's not inside the for loop. It can be instance variable or a public variable. — 8bra1nz, Jan 03 '16 at 08:37

How do I use a variable that is declared inside of a for loop outside the loop?

1 Answers1