Java 多线程进阶-并发数据结构
标签：dde java 多线程 rac ace dma star out except lang
Java 多线程进阶-并发数据结构
- 并发数据结构
- 常用的数据结构是线程不安全的
- ArrayList/HashMap/HashSet 非同步的
- 多个线程同时独写, 可能会抛出异常或数据错误
- 传统Vector/HashTable等同步数据集合性能过差
- 并发数据结构: 数据添加或删除
- 阻塞式集合: 当集合为空或者满时, 等待
- 非阻塞式集合: 当集合为空或者满时, 不等待, 返回null或异常
- List
- Vector 同步安全, 写多读少, 效率差
- ArrayList 不安全
- 通过 基于 synchronized的Collections.synchronizedList(List list) 方法将 List 变成线程安全的, 效率差
- CopyOnWriteArrayList (JDK5提供的基于复制机制的并发列表类), 非阻塞的, 适用于读多写少即填入数据之后大部分操作是读取和遍历的. 效率好, 适合在多线程下使用.
package thread0418;
import java.time.LocalDateTime;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;
/**
* 并发数据结构对比
*/
public class ThreadListDemo1 {
public static void main(String[] args) throws InterruptedException {
// 线程不安全
List unsafeList = new ArrayList();
// 线程安全 将一个不安全的转成安全的
List safeList1 = Collections.synchronizedList(new ArrayList());
// 线程安全
CopyOnWriteArrayList safeList2 = new CopyOnWriteArrayList();
ListThread111 t1 = new ListThread111(unsafeList);
ListThread111 t2 = new ListThread111(safeList1);
ListThread111 t3 = new ListThread111(safeList2);
// 分别启动十个线程, 运行测试
for (int i = 0; i " + t1.list.size());
System.out.println(LocalDateTime.now() + " => " + t2.list.size());
System.out.println(LocalDateTime.now() + " => " + t3.list.size());
// 输出list中的值
System.out.println(LocalDateTime.now() + " => " + "unsafeList:");
for (String s : t1.list) {
if (s == null) {
System.out.print("null ");
} else {
System.out.print(s + " ");
}
}
System.out.println();
System.out.println(LocalDateTime.now() + " => " + "safeList1: ");
for (String s : t2.list) {
if (s == null) {
System.out.print("null ");
} else {
System.out.print(s + " ");
}
}
System.out.println();
System.out.println(LocalDateTime.now() + " => " + "safeList2: ");
for (String s : t3.list) {
if (s == null) {
System.out.print("null ");
} else {
System.out.print(s + " ");
}
}
}
}
class ListThread111 implements Runnable {
public List list;
public ListThread111(List list) {
this.list = list;
}
@Override
public void run() {
int i = 0;
while (i
- Set
- HashSet 不安全
- Collections.synchronizedSet(Set set) 基于 synchronized, 效率差
- CopyOnWriteArraySet (JDK5提供的基于 CopyOnWriteArrayList 实现), 非阻塞的, 适用于读多写少， 效率好, 适合在多线程下使用.
package thread0418;
import java.time.LocalDateTime;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.CopyOnWriteArraySet;
public class ThreadSetDemo1 {
public static void main(String[] args) throws InterruptedException {
// 线程不安全
Set unsafeSet = new HashSet();
// 线程安全
Set safeSet1 = Collections.synchronizedSet(new HashSet());
// 线程安全
CopyOnWriteArraySet safeSet2 = new CopyOnWriteArraySet();
SetThread111 t1 = new SetThread111(unsafeSet);
SetThread111 t2 = new SetThread111(safeSet1);
SetThread111 t3 = new SetThread111(safeSet2);
// 分别启动十个线程, 运行测试
for (int i = 0; i " + t1.set.size());
System.out.println(LocalDateTime.now() + " => " + t2.set.size());
System.out.println(LocalDateTime.now() + " => " + t3.set.size());
// 输出 Set 中的值
System.out.println(LocalDateTime.now() + " => " + "unsafeSet: ");
for (String ele : t1.set) {
if (ele == null) {
System.out.print("null ");
} else {
System.out.print(ele + " ");
}
}
System.out.println();
System.out.println(LocalDateTime.now() + " => " + "safeSet1: ");
for (String ele : t2.set) {
if (ele == null) {
System.out.print("null ");
} else {
System.out.print(ele + " ");
}
}
System.out.println();
System.out.println(LocalDateTime.now() + " => " + "safeSet2: ");
for (String ele : t3.set) {
if (ele == null) {
System.out.print("null ");
} else {
System.out.print(ele + " ");
}
}
}
}
class SetThread111 implements Runnable {
public Set set;
public SetThread111(Set set) {
this.set = set;
}
@Override
public void run() {
int i = 0;
while (i
- Map
- Hashtable 同步安全, 写多读少, 效率差
- HashMap 不安全
- Collections.synchronizedMap(Map map) 基于 synchronized, 效率差
- ConcurrentHashMap 读多写少, 非阻塞
package thread0418;
import java.time.LocalDateTime;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
public class ThreadMapDemo1 {
public static void main(String[] args) throws InterruptedException {
// 线程不安全
MapThread111 t1 = new MapThread111(new HashMap());
// 线程安全
MapThread111 t2 = new MapThread111(Collections.synchronizedMap(new HashMap()));
// 线程安全
MapThread111 t3 = new MapThread111(new ConcurrentHashMap());
// 分别启动十个线程, 运行测试
for (int i = 0; i " + t1.map.size());
System.out.println(LocalDateTime.now() + " => " + t2.map.size());
System.out.println(LocalDateTime.now() + " => " + t3.map.size());
// 输出 map 中的值
System.out.println(LocalDateTime.now() + " => " + "unsafeMap:");
Iterator> iterator = t1.map.entrySet().iterator();
while (iterator.hasNext()) {
Map.Entry entry = iterator.next();
System.out.print(entry.getKey() + ":" + entry.getValue() + " ");
}
System.out.println();
System.out.println(LocalDateTime.now() + " => " + "safeMap:");
iterator = t2.map.entrySet().iterator();
while (iterator.hasNext()) {
Map.Entry entry = iterator.next();
System.out.print(entry.getKey() + ":" + entry.getValue() + " ");
}
System.out.println();
System.out.println(LocalDateTime.now() + " => " + "safeMap2:");
iterator = t3.map.entrySet().iterator();
while (iterator.hasNext()) {
Map.Entry entry = iterator.next();
System.out.print(entry.getKey() + ":" + entry.getValue() + " ");
}
System.out.println();
System.out.println(LocalDateTime.now() + " => " + "mapThread1.map.size()" + t1.map.size());
System.out.println(LocalDateTime.now() + " => " + "mapThread2.map.size()" + t2.map.size());
System.out.println(LocalDateTime.now() + " => " + "mapThread3.map.size()" + t3.map.size());
}
}
class MapThread111 implements Runnable {
public Map map;
public MapThread111(Map map) {
this.map = map;
}
@Override
public void run() {
int i = 0;
while (i
- Queue(单向队列) & Deque(双向队列)(JDK1.5)
- ConcurrentLinkedQueue 非阻塞
- ArrayBlockingQueue/LinkedBlockingQueue 阻塞
package thread0418;
import java.time.LocalDateTime;
import java.util.ArrayDeque;
import java.util.Queue;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.ConcurrentLinkedDeque;
public class ThreadQueueDemo1 {
public static void main(String[] args) throws InterruptedException {
// 线程不安全
QueueThread111 t1 = new QueueThread111(new ArrayDeque());
// 线程安全
QueueThread111 t2 = new QueueThread111(new ConcurrentLinkedDeque());
QueueThread111 t3 = new QueueThread111(new ArrayBlockingQueue(100));
for (int i = 0; i " + t1.queue.size());
System.out.println(LocalDateTime.now() + " => " + t2.queue.size());
System.out.println(LocalDateTime.now() + " => " + t3.queue.size());
// 输出 Queue 中的值
System.out.println("unsafeQueue: ");
for (String s : t1.queue) {
System.out.print(s + " ");
}
System.out.println();
System.out.println("safeQueue1: ");
for (String s : t2.queue) {
System.out.print(s + " ");
}
System.out.println();
System.out.println("safeQueue2: ");
for (String s : t3.queue) {
System.out.print(s + " ");
}
}
}
class QueueThread111 implements Runnable {
public Queue queue;
public QueueThread111(Queue queue) {
this.queue = queue;
}
@Override
public void run() {
int i = 0;
while (i
- 总结
- 了解数据结构并发独写的问题
- 根据业务特点, 使用正确的并发数据结构
Java 多线程进阶-并发数据结构
标签：dde java 多线程 rac ace dma star out except lang
原文地址：https://www.cnblogs.com/sweetXiaoma/p/12737697.html
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