Java等待和notifyAll：IllegalMonitorStateException

我是Java新手（和RoR开发人员）。

我有一个简单的程序。 球是共享的球员。 球应该传递给随机球员。

好的，这里是代码：

class Ball { private int currentPlayer; public void setCurrentPlayer( int currentPlayer, int fromWho ) { this.currentPlayer = currentPlayer; System.out.println( "Ball:setCurrentPlayer " + fromWho + " ---> " + currentPlayer ); } public int getCurrentPlayer() { return currentPlayer; } } class Player implements Runnable { private int myID; private Ball ball; private int playersCount; java.util.Random rnd; public Player(int id, Ball ball, int playersCount) { myID = id; this.ball = ball; this.playersCount = playersCount; rnd = new java.util.Random( id ); } public void run() { int nextPlayer; while (true) { synchronized (ball) { if ( ball.getCurrentPlayer() == myID ) { nextPlayer = rnd.nextInt(playersCount); System.out.println( "Player nr. " + myID + " ---> " + nextPlayer ); ball.setCurrentPlayer( nextPlayer, myID ); ball.notifyAll(); } else { try { wait(); } catch (InterruptedException e) { e.printStackTrace(); } } } } } } class Start { public static void main( String[] argv ) throws Exception { Ball p = new Ball(); System.out.println("MAIN: ball will be in player: " + p.getCurrentPlayer()); final int playersCount = 5; for ( int i = 0; i < playersCount; i++ ) { ( new Thread( new Player( i, p, playersCount ) ) ).start(); } while ( true ) { Thread.sleep( 500 ); System.out.println( "MAIN: ball is in player : " + p.getCurrentPlayer() ); } } } 

但它不起作用。 我得到exception： IllegalMonitorStateException 。

我怎样才能解决这个问题？

Answer 1

你正在等待this显示器而没有同步它; 你需要等待ball