What's the difference between ConcurrentHashMap and Collections.synchronizedMap(Map)?

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来自：http://stackoverflow.com/questions/510632/whats-the-difference-between-concurrenthashmap-and-collections-synchronizedmap
　　　http://javarevisited.blogspot.hk/2011/04/difference-between-concurrenthashmap.html

╔═══════════════╦═══════════════════╦═══════════════════╦═════════════════════╗
║   Property    ║     HashMap       ║    Hashtable      ║  ConcurrentHashMap  ║
╠═══════════════╬═══════════════════╬═══════════════════╩═════════════════════╣ 
║      Null     ║     allowed       ║              not allowed                ║
║  values/keys  ║                   ║                                         ║
╠═══════════════╬═══════════════════╬═════════════════════════════════════════╣
║Is thread-safe ║       no          ║                  yes                    ║
╠═══════════════╬═══════════════════╬═══════════════════╦═════════════════════╣
║     Lock      ║       not         ║ locks the whole   ║ locks the portion   ║        
║  mechanism    ║    applicable     ║       map         ║                     ║ 
╠═══════════════╬═══════════════════╩═══════════════════╬═════════════════════╣
║   Iterator    ║               fail-fast               ║       fail-safe     ║ 
╚═══════════════╩═══════════════════════════════════════╩═════════════════════╝

What's the difference between ConcurrentHashMap and Collections.synchronizedMap(Map)?

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原文地址：http://www.cnblogs.com/sunxucool/p/5477274.html