public void openMist(int x, int y){
if(!inArea(x, y))
throw new IllegalArgumentException("x or y is out of index in openMist function!");
for(int i = x-1 ; i <= x+1 ; i ++)
for(int j = y-1 ; j <= y+1 ; j++)
if(inArea(i,j))
inMist[i][j] = false;
return;
}
}