我试图循环HashMap:
Map<String, Integer> group0 = new HashMap<String, Integer>();
...并提取每个元素group0.这是我的方法:
// iterate through all Members in group 0 that have not been assigned yet
for (Map.Entry<String, Integer> entry : group0.entrySet()) {
// determine where to assign 'entry'
iEntryGroup = hasBeenAccusedByGroup(entry.getKey());
if (iEntryGroup == 1) {
assign(entry.getKey(), entry.getValue(), 2);
} else {
assign(entry.getKey(), entry.getValue(), 1);
}
}
这里的问题是每次调用assign()都会从中删除元素group0,从而修改其大小,从而导致以下错误:
Exception in thread "main" java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextEntry(HashMap.java:793)
at java.util.HashMap$EntryIterator.next(HashMap.java:834)
at java.util.HashMap$EntryIterator.next(HashMap.java:832) …我在迭代列表时删除列表元素时遇到问题.码:
For (WebElement element: list){
if (!element.isEnabled() || !element.isSelected()){
list.remove(element);
}
}
我得到了一个ConcurrentModificationException,我完全理解.我在循环列表中删除列表中的项目.直觉上,这会搞砸循环的索引.
我的问题是,怎么回事我应该删除或者不元素enabled或selected从这个名单？
可能重复:
在迭代Collection时删除元素的高效等效项
private LinkedList flights;
....
public void clear(){
ListIterator itr = flights.listIterator();
while(itr.hasNext()){
flights.remove(itr.next());
}
}
....
Exception in thread "main" java.util.ConcurrentModificationException
at java.util.LinkedList$ListItr.checkForComodification(Unknown Source)
at java.util.LinkedList$ListItr.next(Unknown Source)
at section1.FlightQueue.clear(FlightQueue.java:44)
at section1.FlightTest001.main(FlightTest001.java:22)
它出什么问题了？不能理解为什么会给出错误,我确信我在arraylists或数组上使用了相同的代码并且它已经有效了.
我在我的类中使用了一个Map对象,我已经与LinkedHashMap的Collections.synchronizedMap()同步,如下所示:
private GameObjectManager(){
gameObjects = Collections.synchronizedMap(new LinkedHashMap<String, GameObject>());
}
我在这个函数的第三行得到一个并发修改异常:
public static void frameElapsed(float msElapsed){
if(!INSTANCE.gameObjects.isEmpty()){
synchronized(INSTANCE.gameObjects){
for(GameObject object : INSTANCE.gameObjects.values()){...}
}
}
}
我正在迭代Map的所有其他位置,我按照文档同步地图.
我的类中还有其他函数使用这个Map(同步的!)和put()和remove()对象,但这应该无关紧要.我究竟做错了什么？请询问更多代码,不知道还能提供什么.
哦,和日志消息:
08-20 15:55:30.109: E/AndroidRuntime(14482): FATAL EXCEPTION: GLThread 1748
08-20 15:55:30.109: E/AndroidRuntime(14482): java.util.ConcurrentModificationException
08-20 15:55:30.109: E/AndroidRuntime(14482): at java.util.LinkedHashMap$LinkedHashIterator.nextEntry(LinkedHashMap.java:350)
08-20 15:55:30.109: E/AndroidRuntime(14482): at java.util.LinkedHashMap$ValueIterator.next(LinkedHashMap.java:374)
08-20 15:55:30.109: E/AndroidRuntime(14482): at package.GameObjectManager.frameElapsed(GameObjectManager.java:247)
08-20 15:55:30.109: E/AndroidRuntime(14482): at package.GamekitInterface.render(Native Method)
08-20 15:55:30.109: E/AndroidRuntime(14482): at package.GamekitInterface.renderFrame(GamekitInterface.java:332)
08-20 15:55:30.109: E/AndroidRuntime(14482): at com.qualcomm.QCARSamples.ImageTargets.GameEngineInterface.onDrawFrame(GameEngineInterface.java:107)
08-20 15:55:30.109: E/AndroidRuntime(14482): at android.opengl.GLSurfaceView$GLThread.guardedRun(GLSurfaceView.java:1516)
08-20 15:55:30.109: E/AndroidRuntime(14482): at android.opengl.GLSurfaceView$GLThread.run(GLSurfaceView.java:1240)
java multithreading synchronized linkedhashmap concurrentmodification
这是我的代码:
for (int i = 0; i < myarraylist.size(); i++) {
for (int j = 0; j < stopwords.size(); j++) {
if (stopwords.get(j).equals(myarraylist.get(i))) {
myarraylist.remove(i);
id.remove(i);
i--; // to look at the same index again!
}
}
}
我有问题..删除元素后,所有索引总是改变,上面的循环太乱了.
为了说明:我有54个数据,但上面的循环在元素删除后变得混乱..因此只检查了50个数据.
有没有其他方法或修复我的代码以索引删除多个元素？元素索引对我来说非常重要,要删除具有相同索引的另一个arraylist.
所以我有两个线程在运行,其中一个线程应该从用户获取信息,另一个线程假设使用用户提供的信息,如下所示:
public class UserRequest implements Runnable {
@Override
public void run() {
// TODO Auto-generated method stub
String request;
Scanner input = new Scanner(System.in);
while(true)
{
System.out.println("Please enter request:");
request = input.nextLine();
try
{
//do something
}
catch(IOException e)
{
e.printStackTrace();
}
}
}
第二个帖子:
public class Poller implements Runnable {
ArrayList<String> colors = new ArrayList<String>();
public void poll()
{
for(String color : colors)
{
if(color == "")
{
//do work
}
else
{
//do work
}
}
}
@Override …Exception in thread "main" java.util.ConcurrentModificationException
Squash the PC dirties the room Violet. The room's state is now dirty
Lily the animal growls
The Animal Lily left the room and goes to Green through the west door.
at java.util.HashMap$HashIterator.nextEntry(HashMap.java:793)
at java.util.HashMap$KeyIterator.next(HashMap.java:828)
at homework5.Room.critReactRoomStateChange(Room.java:76)
at homework5.PC.play(PC.java:121)
at homework5.Main.main(Main.java:41)
Java Result: 1
这是我收到的错误.
我的方法看起来像
public void critReactRoomStateChange(String command, PC pc) {
Creature temp = null;
Iterator iterator = getCreatures().keySet().iterator();
while (iterator.hasNext()) {
String names = iterator.next().toString();
if (!(getCreatures().get(names) instanceof PC)) {
temp = …我正在尝试创建一个霍夫曼树,并且正在尝试合并两棵树.我无法弄清楚如何在没有得到"并发修改异常"的情况下删除程序中的树,因为我正在迭代列表并尝试同时从列表中删除.
BinaryTree<Character, Integer> t1 = null;
BinaryTree<Character, Integer> t2 = null;
BinaryTree<Character, Integer> tFinal = null;
int treeSize = TREES.size();
for (int i = 0; i < treeSize; i++) {
for (BinaryTree<Character, Integer> t : TREES) {
System.out.println("treeSize " + treeSize);
System.out.println(t.getRoot().getElement()
+ " t.getRoot().getElement()");
// here I edited the merge function in Binary Tree to set
// the new root
// to have null value for value, and itemTwo for weight
System.out.println(t.getRoot().getValue() + " weight of tree \n");
t1 …我试图找出让多个线程在同一个字符串列表中工作的最佳方法.例如,假设我有一个单词列表,我想要多个线程来打印出这个列表中的每个单词.
这就是我想出的.该线程使用while循环,当迭代器具有next时,它会打印出来并从列表中删除它.
import java.util.*;
public class ThreadsExample {
static Iterator it;
public static void main(String[] args) throws Exception {
ArrayList<String> list = new ArrayList<>();
list.add("comet");
list.add("planet");
list.add("moon");
list.add("star");
list.add("asteroid");
list.add("rocket");
list.add("spaceship");
list.add("solar");
list.add("quasar");
list.add("blackhole");
it = list.iterator();
//launch three threads
RunIt rit = new RunIt();
rit.runit();
rit.runit();
rit.runit();
}
}
class RunIt implements Runnable {
public void run()
{
while (ThreadsExample.it.hasNext()) {
//Print out and remove string from the list
System.out.println(ThreadsExample.it.next());
ThreadsExample.it.remove();
}
}
public void runit() {
Thread thread …我有 2 个 Main 类的内部线程类。有时，当一个添加新元素而另一个被删除时，它会导致 ConcurrentModificationException。我想我不知道如何同步它们。
Class Main{
HashSet<MyObject> set;
Thread A{
run(running){
...
set.add(obj);
...
}
}
Thread B{
run(){
while (running) {
for (Iterator<MyObject> i = set.iterator(); i.hasNext();) {
MyObject obj= i.next();
if (!obj.isSmt()) {
i.remove();
...
}
}
}
}
}
}
java ×10
arraylist ×3
iterator ×2
android ×1
concurrency ×1
exception ×1
hashmap ×1
linked-list ×1
stop-words ×1
string ×1
synchronized ×1