Hashmap cotainskey 结果有问题

Key: HashMapTest$KeyCheck@5 Get: Success Contains: true Key: HashMapTest$KeyCheck@a Get: null Contains: false Key: HashMapTest$KeyCheck@5 Get: null Co...

import java.util.concurrent.ConcurrentHashMap; 56 import java.util.concurrent.ConcurrentMap; 57 import java.util.jar.JarEntry; Resource bundles contain locale...

I have a HashMap for storing objects: private Map<T, U> fields = Collections.synchronizedMap(new HashMap<T, U>()); but, when trying to check exi...

Some Map implementations are allowed to have null values, eg HashMap, in this case if get(key) returns null it does not guarantee that there is no ...

(Some maps - Hashtable and ConcurrentHashMap, at least - don't allow null values, which makes containsKey less important there, but it's still a nic...