下面的代码导致 Exception in thread "main" java.util.ConcurrentModificationException 错误。
我正在尝试使用一个增强的for循环来迭代我的无人机阵列列表，以更新它们的位置和方向。以下代码仅适用于arraylist中的1个无人机。 tryToMove() 获取无人机的方向，将其移动到相应的x，y并检查其是否有效，如果无效，则更改方向。 doDisplay() 打印控制台中有无人机的竞技场。

public static void moveAllDrones(){
    String strOfCurrentDirection;
    Direction currentDirection;

    for (String drone : drones) {
        id = drones.indexOf(drone);
        System.out.println("Working on drone: " + id);
        String[] coords = drone.split(",");
        accX = Integer.parseInt(coords[0]);//get x coordinate
        accY = Integer.parseInt(coords[1]);// get y coordinate

        String droneWithCurrentID = drones.get(id); //direction in string
        strOfCurrentDirection = droneWithCurrentID.split(",")[2];
        currentDirection = Direction.valueOf(strOfCurrentDirection); //convert string to direction

        Drone.tryToMove(id, currentDirection, accX, accY);
    }
    DroneInterface.doDisplay();
}

我不知道为什么这个增强的for循环只适用于1架无人机。谢谢你的帮助。
更新：

public static void tryToMove(int id2, Direction accDir, int x1, int y1) {
        xPos = x1;
        yPos = y1;
        //Direction d = Drone.direction; // get current direction drone is facing.
        System.out.println("Trying to move drone, "+id2+ ". In the direction of: "+accDir);
        switch (accDir) {

        case NORTH: 
            yPos -= 1;
            if (DroneArena.canMoveHere(xPos, yPos)) {

                DroneArena.yRan = yPos;

            } else {
                yPos += 1;
                accDir = Direction.nextDirection();
            }
            DroneArena.updateDrone(id2, accDir, xPos, yPos);
            break;
        case EAST:

            xPos += 1;
            if (DroneArena.canMoveHere(xPos, yPos)) {

                DroneArena.xRan = xPos;

            } else {
                xPos -= 1;
                accDir = Direction.nextDirection();
            }
            DroneArena.updateDrone(id2, accDir, xPos, yPos);
            break;
        case SOUTH:

            yPos += 1;
            if (DroneArena.canMoveHere(xPos, yPos)) {
                DroneArena.yRan = yPos;

            } else {
                yPos -= 1;
                accDir = Direction.nextDirection();
            }
            DroneArena.updateDrone(id2, accDir, xPos, yPos);
            break;
        case WEST:

            xPos -= 1;
            if (DroneArena.canMoveHere(xPos, yPos)) {

                DroneArena.xRan = xPos;

            } else {
                xPos += 1;
                accDir = Direction.nextDirection();
            }
            DroneArena.updateDrone(id2, accDir, xPos, yPos);
            break;

        }
    }

更新无人机：

public static void updateDrone(int id2, Direction direction, int newX, int newY){

        updatedDirection = direction;
        DroneArena.direction = updatedDirection;
        drones.remove(id2);
        drones.add(id2, newX + "," + newY +"," + updatedDirection);

    }