java并发初探ConcurrentSkipListMap
2024-09-06 22:51:53
java并发初探ConcurrentSkipListMap
ConcurrentSkipListMap以调表这种数据结构以空间换时间获得效率，通过volatile和CAS操作保证线程安全，而且它保证了有序性，比TreeMap比线程安全。
跳表结构
通过level down right可以更快插入和查找元素
*
* Head nodes Index nodes
* +-+ right +-+ +-+
* |2|---------------->| |--------------------->| |->null
* +-+ +-+ +-+
* | down | |
* v v v
* +-+ +-+ +-+ +-+ +-+ +-+
* |1|----------->| |->| |------>| |----------->| |------>| |->null
* +-+ +-+ +-+ +-+ +-+ +-+
* v | | | | |
* Nodes next v v v v v
* +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+
* | |->|A|->|B|->|C|->|D|->|E|->|F|->|G|->|H|->|I|->|J|->|K|->null
* +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+
例子
package com.java.javabase.thread.collection;
import lombok.extern.slf4j.Slf4j;
import java.security.SecureRandom;
import java.util.Iterator;
import java.util.Map;
import java.util.Random;
import java.util.TreeMap;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentSkipListMap;
/**
* @author
*/
@Slf4j
public class ConcurrentSkipMapTest {
//public static TreeMap<String, Integer> map = new TreeMap();
public static ConcurrentSkipListMap<String, Integer> map = new ConcurrentSkipListMap<>();
public static int size = 10;
public static void main(String[] args) {
InnerThread t1 =new InnerThread("t1");
InnerThread t2 =new InnerThread("t2");
t1.start();
t2.start();
try {
Thread.sleep(1000);
printMap(map);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
static class InnerThread extends Thread {
String name;
public InnerThread(String name) {
super(name);
this.name=name;
}
@Override
public void run() {
Random random = new Random(System.currentTimeMillis());
for (int i = 0; i < size; i++) {
String key =String.valueOf(random.nextInt(1000))+name;
//Wlog.info(key);
map.put(key, Integer.valueOf(i));
printMapNone(map);
}
}
}
public static void printMap(Map<String, Integer> map) {
//Iterator<Map.Entry<K,V>> i = entrySet().iterator();
Iterator<Map.Entry<String, Integer>> it = map.entrySet().iterator();
while (it.hasNext()) {
Map.Entry<String, Integer> entry = it.next();
String key = entry.getKey();
Integer value = entry.getValue();
log.info("key {} value {}", key, value);
}
}
public static void printMapNone(Map<String, Integer> map) {
//Iterator<Map.Entry<K,V>> i = entrySet().iterator();
Iterator<Map.Entry<String, Integer>> it = map.entrySet().iterator();
while (it.hasNext()) {
Map.Entry<String, Integer> entry = it.next();
String key = entry.getKey();
Integer value = entry.getValue();
}
}
}
run result
019-08-28 19:34:31,919 [main] INFO ConcurrentSkipMapTest - key 101t1 value 5
2019-08-28 19:34:31,921 [main] INFO ConcurrentSkipMapTest - key 101t2 value 5
2019-08-28 19:34:31,921 [main] INFO ConcurrentSkipMapTest - key 131t1 value 7
2019-08-28 19:34:31,921 [main] INFO ConcurrentSkipMapTest - key 131t2 value 7
2019-08-28 19:34:31,922 [main] INFO ConcurrentSkipMapTest - key 180t1 value 3
2019-08-28 19:34:31,922 [main] INFO ConcurrentSkipMapTest - key 180t2 value 3
2019-08-28 19:34:31,922 [main] INFO ConcurrentSkipMapTest - key 209t1 value 9
2019-08-28 19:34:31,922 [main] INFO ConcurrentSkipMapTest - key 209t2 value 9
2019-08-28 19:34:31,922 [main] INFO ConcurrentSkipMapTest - key 349t1 value 6
2019-08-28 19:34:31,922 [main] INFO ConcurrentSkipMapTest - key 349t2 value 6
2019-08-28 19:34:31,923 [main] INFO ConcurrentSkipMapTest - key 527t1 value 4
2019-08-28 19:34:31,923 [main] INFO ConcurrentSkipMapTest - key 527t2 value 4
2019-08-28 19:34:31,923 [main] INFO ConcurrentSkipMapTest - key 655t1 value 1
2019-08-28 19:34:31,923 [main] INFO ConcurrentSkipMapTest - key 655t2 value 1
2019-08-28 19:34:31,923 [main] INFO ConcurrentSkipMapTest - key 714t1 value 8
2019-08-28 19:34:31,923 [main] INFO ConcurrentSkipMapTest - key 714t2 value 8
2019-08-28 19:34:31,923 [main] INFO ConcurrentSkipMapTest - key 781t1 value 2
2019-08-28 19:34:31,924 [main] INFO ConcurrentSkipMapTest - key 781t2 value 2
2019-08-28 19:34:31,924 [main] INFO ConcurrentSkipMapTest - key 797t1 value 0
2019-08-28 19:34:31,924 [main] INFO ConcurrentSkipMapTest - key 797t2 value 0
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