Question

我想将函数返回的值放入ConcurrentHashmap，就像那样

private static ConcurrentHashMap<String, Object> map = new ConcurrentHashMap<String, Object>();

public void process() {
    map.put(key, function());
}

public Object function() {
    return anyObject;
}

我可以知道函数（例如function（））是否是线程安全的？请告知是否有任何教程感谢。

Answer 1

调用自身不是线程安全的，只是把操作放在原子上。

相反，你可以使用番石榴

ConcurrentMap<Key, Graph> graphs = new MapMaker()
   .concurrencyLevel(4)
   .weakKeys()
   .maximumSize(10000)
   .expireAfterWrite(10, TimeUnit.MINUTES)
   .makeComputingMap(
       new Function<Key, Graph>() {
         public Graph apply(Key key) {
           return createExpensiveGraph(key);
         }
       });

请注意 makeComputingMap（）调用

http://docs.guava-libraries.googlecode.com/git/javadoc/com/google/common/collect/MapMaker.html

Answer 2

您可以使用Java中的读/写锁。

示例：

class X {
  ReadWriteLock rw;

  public void read() throws InterruptedException { 
    rw.readLock().acquire();
    try {
      // ... do the read
    } finally {
      rw.readlock().release()
    }
 }

 public void write() throws InterruptedException { 
     rw.writeLock().acquire();
     try {
       // ... do the write
     } finally {
       rw.writelock().release()
     }
   }
 }

参考：

http://www.coderanch.com/t/232685/threads/java/Concurrent-access-HashMap http://docs.oracle.com/javase/1.5.0/docs/api/java/util/concurrent/locks/ReadWriteLock.html http://tutorials.jenkov.com/java-concurrency/read-write-locks.html

java：hashmap.put（key，function（））中的函数是否是线程安全的？

2 个答案: