public void initiateEnemy() { ArrayList<Position> pos_list = new ArrayList<Position>(); for (int i = 0; i < sizex / BomborMan.unit; i++) { for (int j = 0; j < sizex / BomborMan.unit; j++) { BlockType blk = getMapState(i, j).getBlockType(); if (blk == BlockType.EMPTY) { pos_list.add(getMapState(i, j).getPosition()); } } } int size_pos = pos_list.size(); for (int i = 0; i < BomborMan.enemyNum; i++) { int in = (int) (Math.random() * size_pos); Position temp = pos_list.get(in); Enemy en = new Enemy(BlockType.ENEMY, temp, null); en.start(); enList.add(en); } }