Java集合源码学习(23)_Map的子接口ConcurrentMap

定义了几个原子的操作方法:

Method Summary VputIfAbsent(K key, V value) 
          If the specified key is not already associated with a value, associate it with the given value. booleanremove(Object key, Object value) 
          Removes the entry for a key only if currently mapped to a given value. Vreplace(K key, V value) 
          Replaces the entry for a key only if currently mapped to some value. booleanreplace(K key, V oldValue, V newValue) 
          Replaces the entry for a key only if currently mapped to a given value.

Method Summary VputIfAbsent(K key, V value) 
          If the specified key is not already associated with a value, associate it with the given value. booleanremove(Object key, Object value) 
          Removes the entry for a key only if currently mapped to a given value. Vreplace(K key, V value) 
          Replaces the entry for a key only if currently mapped to some value. booleanreplace(K key, V oldValue, V newValue) 
          Replaces the entry for a key only if currently mapped to a given value.