Question

so im programming conways game of life in GUI form. the output is not correct and i dont know why. this is the code that handles the “next generation”.

for(int i=0; i < ROW; i++) {
    for(int j=0; j < COL; j++) {
        if(i > 0 && i < ROW-1 && j > 0 && j < COL -1) {
            if(grid.getButton(i-1, j-1).getBackground() == Color.BLUE) liveNeighbor++;
            if(grid.getButton(i-1, j).getBackground() == Color.BLUE) liveNeighbor++;
            if(grid.getButton(i-1, j+1).getBackground() == Color.BLUE) liveNeighbor++;
            if(grid.getButton(i, j-1).getBackground() == Color.BLUE) liveNeighbor++;
            if(grid.getButton(i, j+1).getBackground() == Color.BLUE) liveNeighbor++;
            if(grid.getButton(i+1, j-1).getBackground() == Color.BLUE) liveNeighbor++;
            if(grid.getButton(i+1, j).getBackground() == Color.BLUE) liveNeighbor++;
            if(grid.getButton(i+1, j+1).getBackground() == Color.BLUE) liveNeighbor++;

            if(grid.getButton(i, j).getBackground() == Color.WHITE) {
                if(liveNeighbor == 3) 
                    newGrid.getButton(i, j).setBackground(Color.BLUE);
                } else {
                    if(liveNeighbor > 3 || liveNeighbor < 2) 
                        newGrid.getButton(i, j).setBackground(Color.WHITE);
            }
            liveNeighbor=0;
        }
    }
}

maybe im missing something, but im pretty sure this is right. any suggestions?

Answer 1

This is the problem:

if(grid.getButton(i, j).getBackground() == Color.WHITE) {
    if(liveNeighbor == 3) 
        newGrid.getButton(i, j).setBackground(Color.BLUE);
    } else {
        if(liveNeighbor > 3 || liveNeighbor < 2) 
            newGrid.getButton(i, j).setBackground(Color.WHITE);
}

Your code only sets the color if the current tile is dead. If it’s alive, it will never become dead. I would write this as:

boolean currentlyAlive = grid.getButton(i, j).getBackground() == Color.BLUE;
boolean aliveNextStep = (liveNeighbour == 3) ||
                        (currentlyAlive && liveNeighbor == 2);
newGrid.getButton(i, j).setBackground(aliveNextStep ? Color.BLUE : Color.WHITE);

I’d also separate the logical data (a grid of boolean values) from the display part – the “business logic” here shouldn’t know anything about colors.