CC150:5.8

public class Question5_8 {
    public void drawHorizontalLine(byte[] screen, int width, int x1, int x2, int y) {
        int height = screen.length / (width / 8);
        if (y < 0 || y >= height || x1 < 0 || x1 >= screen.length * 8 || x2 < 0 || x2 >= screen.length * 8) {
            return;
        }
        
        int idx = y * (width / 8);
        int idx1 = idx + (x1 / 8);
        int idx2 = idx + (x2 / 8);
        
        for (int i = idx1 + 1; i < idx2; ++i) {
            screen[i] = (byte) 0xFF;
        }
 
        byte mask1 = (byte) (0xff >>> x1 % 8);
        byte mask2 = (byte) (~((1 << (7 - x2 % 8)) - 1));
        if (idx1 == idx2) {
            screen[idx1] |= (mask1 & mask2);
        } else {
            screen[idx1] |= mask1;
            screen[idx2] |= mask2;
        }
    }
    
    
    public static void main(String[] args) {
    
         public static void main(String[] args) {
	int screen[] =  new int[]{0, 0, 0, 0, 0, 0, 1，1，1，1，1，1};
	int width = 32;
	//showScreen(screen, width);
	drawHorizontalLine(screen, width, 2, 7, 1);
	showScreen(screen, width);
    }
    }
}