“线程 1”java.lang.IndexOutOfBoundsException

Question

我的代码是：

 public class Application {
public static void main(String args[]) throws InterruptedException{
    Fifo f = new Fifo();

    Producer pr = new Producer("elso",f);

    pr.go();


    Thread.sleep(2000);
    Consumer cr = new Consumer("csacsi",f,1000);
    cr.start();
}
 } 

 public class Producer extends Thread{

String szoveg;
int szam;
Fifo ff;

Producer(String s, Fifo f){ ff = f; szoveg =s; szam = 0; }

public void go(){
        start();
}

public void run(){
    while(szam<6)
    try {
        sleep(1000);

        ff.put(szoveg+ " "+szam);
        System.out.println("producer" +" " +ff.get()+" "+System.currentTimeMillis()%100000);
        //System.out.println(szoveg +" "+ szam+ "     "+System.currentTimeMillis()%100000);
        szam++;
    } catch (InterruptedException e) {
        System.out.println("fasz");
    }

    //szam+=1;
}
 }

 import java.util.ArrayList;

 public class Fifo {

ArrayList<String> str = new ArrayList<String>();


 synchronized void put(String s) throws InterruptedException{
    while(str.size()>9){

        //Thread.sleep(10); 
    }
    str.add(s);
}

String get() throws InterruptedException{
    synchronized(str){
     if(str.size()==0) str.wait();
     if(str.size()!=0) str.notifyAll();
         //Thread.sleep(10);
     String s = str.get(0);
     str.remove(0);
     return s;}
 }
 }


 public class Consumer extends Thread{
Fifo F;
String S;
int I,asd;

Consumer (String s, Fifo f, int i){
    F=f; S=s; I=i;
}

public void run(){
    while(asd<6){
        try {
            sleep(I);
            System.out.println("consumer "+F.get());
            asd++;
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}
 }

和输出：

producer elso 0 34491
producer elso 1 35493
producer elso 2 36493Exception in thread "Thread-1" 
java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
at java.util.ArrayList.rangeCheck(Unknown Source)
at java.util.ArrayList.get(Unknown Source)
at alap.Fifo.get(Fifo.java:24)
at alap.Consumer.run(Consumer.java:16)
producer elso 3 37495
producer elso 4 38496
producer elso 5 39496

那么，我的错误是什么？

Answer 1

当您使用synchronized 时，您需要在两个线程中的完全相同的实例上进行同步，这两个线程应该相互保护，否则不会达到预期的效果。

你的put方法在this上同步，而你的get方法在str上同步，这是两个不同的对象，所以没有必要的保护作用。