java.util.concurrent.CopyOnWriteArrayList

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.CopyOnWriteArrayList;

public class TestCalc {
/**
*read
*/
private static class ReadTask implements Runnable {
List<String> list;

public ReadTask(List<String> list) {
this.list = list;
}

public void run() {
for (String str : list) {
System.out.println(str);
}
}
}
/**
*write
*
*/
private static class WriteTask implements Runnable {
List<String> list;
int index;

public WriteTask(List<String> list, int index) {
this.list = list;
this.index = index;
}

public void run() {
list.remove(index);
list.add(index, "write_" + index);
}
}

public void run() {
final int NUM = 10;
//List<String> list = new ArrayList<String>(); //java.util.ConcurrentModificationException
CopyOnWriteArrayList<String> list = new CopyOnWriteArrayList<String>();
for (int i = 0; i < NUM; i++) {
list.add("main_" + i);
}
ExecutorService executorService = Executors.newFixedThreadPool(NUM);
for (int i = 0; i < NUM; i++) {
executorService.execute(new ReadTask(list));
executorService.execute(new WriteTask(list, i));
}
executorService.shutdown();
}

public static void main(String[] args) {
new TestCalc().run();
}
}

/*

//List<String> list = new ArrayList<String>();
Exception in thread "pool-1-thread-11" java.util.ConcurrentModificationException

at java.util.ArrayList$Itr.checkForComodification(Unknown Source)
at java.util.ArrayList$Itr.next(Unknown Source)
at TestCalc$ReadTask.run(TestCalc.java:19)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
*/