Java 反复启动和停止几个线程

我有一个网格（矩阵）。每个单元都是一个对象。一开始，有五个（随机）的这些单元被选为“跳跃单元”，用户可以在其中跳跃以逃离敌人。每个单元格都有一个随机倒计时。如果倒计时变为0，该单元格将变为正常单元格，玩家无法再跳入该单元格。如果用户按Enter键，玩家将跳入当前的一个“跳转单元格”，同时随机选择一个新的跳转单元格

有时候，当我玩这个游戏并按Enter键时，我会得到一个

ConcurrentModificationException

，我不知道为什么

可以按Esc键重置网格情况（创建新的5个跳转单元格）。 如果我反复按Esc按钮，经常会发生一些新的跳转单元没有减少其倒计时

代码如下：

单元格

public class Cell implements Runnable {

/** indicates whether this cell is the target cell */
private boolean isTarget;

/** indicates whether this cell is a jump cell */
private boolean isJumpCell;

/** associated number to this cell */
private int number;

/** living time of this cell */
private int countdown;

/** coordinates of this cell in the grid */
private int i;
private int j;

private boolean running;
private boolean alreadyStarted;

private Thread countdownT;

public Cell(int i, int j) {
    this.i = i;
    this.j = j;
    countdown = (int)(Math.random() * 6) + 3;
    countdownT = new Thread(this);
}

/**
 * Starts the thread or restart if already started in the past
 */
public void start() {
    if(alreadyStarted) {
        restart();
    } else {
        countdownT.start();
        running = true;
        alreadyStarted = true;
        isJumpCell = true;
    }
}

/**
 * This cell is restarted
 */
public void restart() {
    isJumpCell = true;
    running = true;
    countdown = (int)(Math.random() * 6) + 3;
}

/**
 * Stops the update of this cell (is not a jump cell anymore)
 */
public void stop() {
    isJumpCell = false;
    running = false;
}

@Override
public void run() {
    while (running) {
        try {
            Thread.sleep(1000);
            countdown--;
            // if the countdown becomes 0, stop running
            // not a jump cell anymore
            if (countdown == 0) {
                running = false;
                isJumpCell = false;
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

网格

public class TimerThread implements Runnable {

private Grid grid;

private boolean isRunning;

public TimerThread(Grid grid) {
    this.grid = grid;
}

public void start() {
    isRunning = true;
}

public void stop() {
    isRunning = false;
}

@Override
public void run() {
    while(isRunning) {
        // retrieves the list of the jump cells
        ArrayList<Cell> jumpCells = (ArrayList<Cell>) grid.getJumpCells();

        // wait one second
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        // updates the jump cells
        for(Cell c : jumpCells) {
            if(c.getCountdown() > 0) {
                c.decreaseCountdown();
            } else {
                c.setJumpCell(false);
            }
        }
    }
}

我把基本代码

public Grid(RedEnemy p) {
    this.p = p;
    grid = new Cell[ROWS][COLS];
    for(int i = 0; i < ROWS; i++) {
        for(int j = 0; j < COLS; j++) {
            grid[i][j] = new Cell(i,j);
        }
    }
    jumpCells = new ArrayList<Cell>();

    // initial setup
    numJumpCells = 5;

    grid[target_y][target_x].setTarget(true);

    for(int n = 0; n < numJumpCells; n++) {
        int i = (int) (Math.random() * (ROWS - 1)); 
        int j = (int) (Math.random() * (COLS - 1)); 
        grid[i][j].setTarget(false);
        grid[i][j].setNumber(n + 1);
        jumpCells.add(grid[i][j]);
        jumpCells.get(n).start();
    }
}

public void reset() {
    for(Cell cell : jumpCells) {
        cell.stop();
    }
    jumpCells.clear();
    target_x = 0;
    target_y = 0;
    numJumpCells = 5;
    for(int n = 0; n < numJumpCells; n++) {
        int i = (int) (Math.random() * (ROWS - 1)); 
        int j = (int) (Math.random() * (COLS - 1)); 
        grid[i][j].setTarget(false);
        grid[i][j].setNumber(n + 1);
        jumpCells.add(grid[i][j]);
        jumpCells.get(n).start();
    }
}

/**
 * Performs the jump
 */
public void jump() {
    // always jumps in the first jump cell among the current ones
    Cell jumpCell = jumpCells.get(0); 
    // updates the position of the player
    target_y = jumpCell.getI();
    target_x = jumpCell.getJ();
    // updates the cell in the grid
    grid[jumpCell.getI()][jumpCell.getJ()].setJumpCell(false);
    grid[jumpCell.getI()][jumpCell.getJ()].setTarget(true);
    // stop the cell in which the player is jumped
    jumpCells.get(0).stop();
    // removes the cell from the list of the jump cells
    jumpCells.remove(0);

    // updates the position of the player in the enemy class
    p.setTargetY(target_y * SIZE);
    p.setTargetX(target_x * SIZE);

    // create a new jump cell at random
    int i = (int) (Math.random() * (ROWS - 1)); 
    int j = (int) (Math.random() * (COLS - 1)); 
    //grid[i][j].setJumpCell(true);
    grid[i][j].setTarget(false);
    grid[i][j].setNumber(jumpCells.size() - 1);
    jumpCells.add(grid[i][j]);
    jumpCells.get(jumpCells.size() - 1).start();
}

// UPDATE
public void update(float delta) {
    for(Iterator<Cell> it = jumpCells.iterator(); it.hasNext();) {
        Cell c = it.next();
        if(!c.isJumpCell()) {
            it.remove();
            numJumpCells--;
        }
    }
}

// DRAW
public void draw(Graphics dbg) {
    // draw the grid
    dbg.setColor(Color.BLACK);
    int heightOfRow = GamePanel.PHEIGHT / ROWS;
    for (int i = 0; i < ROWS; i++)
        dbg.drawLine(0, i * heightOfRow, GamePanel.PWIDTH, i * heightOfRow);

    int widthdOfRow = GamePanel.PWIDTH / COLS;
    for (int i = 0; i < COLS; i++)
        dbg.drawLine(i * widthdOfRow, 0, i * widthdOfRow, GamePanel.PHEIGHT);

    // draw jump cells
    dbg.setColor(Color.RED);
    dbg.setFont(new Font("TimesRoman", Font.PLAIN, 25)); 
    for(Iterator<Cell> it = jumpCells.iterator(); it.hasNext();) {
        Cell c = it.next();
        dbg.drawRect(c.getJ() * SIZE, c.getI() * SIZE, SIZE, SIZE);
        dbg.setColor(Color.BLUE);
        dbg.drawString(String.valueOf(c.getCountdown()), c.getJ() * SIZE + SIZE/2, c.getI() * SIZE + SIZE/2);
        dbg.setColor(Color.RED);
    }

    // draw target
    dbg.setColor(Color.BLUE);
    dbg.fillRect(target_x * SIZE, target_y * SIZE, SIZE, SIZE);
}

公共电网（RedEnemy p）{
这个，p=p；
网格=新单元格[行][COLS]；
对于（int i=0；i

编辑

时间读取

public class TimerThread implements Runnable {

private Grid grid;

private boolean isRunning;

public TimerThread(Grid grid) {
    this.grid = grid;
}

public void start() {
    isRunning = true;
}

public void stop() {
    isRunning = false;
}

@Override
public void run() {
    while(isRunning) {
        // retrieves the list of the jump cells
        ArrayList<Cell> jumpCells = (ArrayList<Cell>) grid.getJumpCells();

        // wait one second
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        // updates the jump cells
        for(Cell c : jumpCells) {
            if(c.getCountdown() > 0) {
                c.decreaseCountdown();
            } else {
                c.setJumpCell(false);
            }
        }
    }
}

公共类TimerThread实现可运行{
私有电网；
私有布尔运算；
公共时间读取（网格）{
this.grid=grid；
}
公开作废开始（）{
isRunning=true；
}
公共停车场（）{
isRunning=false；
}
@凌驾
公开募捐{
同时（正在运行）{
//检索跳转单元格的列表
ArrayList jumpCells=（ArrayList）grid.getJumpCells（）；
//等一下
试一试{
睡眠（1000）；
}捕捉（中断异常e）{
e、 printStackTrace（）；
}
//更新跳转单元格
用于（单元c：跳线单元）{
如果（c.getCountdown（）>0）{
c、 递减倒计时（）；
}否则{
c、 setJumpCell（假）；
}
}
}
}

或者

@覆盖
公开募捐{
同时（正在运行）{
//检索所有单元格
单元格[][]单元格=grid.getGrid（）；
//等一下
试一试{
睡眠（1000）；
}捕捉（中断异常e）{
e、 printStackTrace（）；
}
//更新单元格
对于（int i=0；i0）{
单元格[i][j]。递减倒计时（）；
}否则{
单元格[i][j].setJumpCell（假）；
}
}
}
}
}
}

好的