多线程之集合类

 

  CopyOnWriteArrayList 

  ConcurrentHashMap

  CopyOnWriteArraySet

 

 public class SynCollectionTest {

 //1.同步list: 每个线程都添加一个元素，看总数
 private CopyOnWriteArrayList<String> list = new CopyOnWriteArrayList<String>(); //线程安全
 //private List<String> list = new ArrayList<String>(); //线程不安全、会报错
 
 public static void main(String[] args) {
  SynCollectionTest o = new  SynCollectionTest();
  for(int i=0;i<100;i++) {
   o.new ListThread().start();
  }
 }

 class ListThread extends Thread{
  
  public void run() {
   list.add("str");
   System.out.println(list.size());
  }
 }
}

public class SynMapTest {
 
 private ConcurrentHashMap<String, Integer> map = new ConcurrentHashMap<String, Integer>(); //线程安全，键、值不能为空值
 //private Hashtable<String, Integer> map = new Hashtable<String, Integer>(); //线程不安全
 //private HashMap<String, Integer> map = new HashMap<String, Integer>(); //线程不安全，抛出异常

 public static void main(String[] args) {
  SynMapTest o = new SynMapTest();
  for(int n=0;n<1000;n++) {
   o.map.put("s"+n, new Integer(0));
  }
  //并发删除,抛出异常 java.util.ConcurrentModificationException
  for(int i=0;i<10;i++) {
   o.new MapThread().start();
  }
 }

 class MapThread extends Thread{
  public void run() {
   Set<String> keys = map.keySet();
   for(String k : keys) {
    map.remove(k);
   }
  }
 }
}

public class SynSet {

 private CopyOnWriteArraySet<String> set = new CopyOnWriteArraySet<String>(); //线程安全
 //private Set<String> set = new HashSet<String>(); //线程不安全，抛出异常java.util.ConcurrentModificationException
 
 private Random r = new Random();
 
 public static void main(String[] args) {
  SynSet o = new SynSet();
  for(int i=0;i<1000;i++) {
   o.set.add(String.valueOf(o.r.nextInt(1000)));
  }
  
  for(int i=0;i<10000;i++) {
   o.new SetThread().start();
  }
 }
 
 class SetThread extends Thread{
  
  public void run() {
   Iterator<String> keys = set.iterator();
   String k = null;
   while(keys.hasNext()) {
    k = keys.next();
    set.remove(k);
   }
  }
 }

}

 

 

 

评论

1 楼 mike_eclipse 2018-04-25  

Hashtable是线程不安全的吗？好像是线程安全的吧？