56. Legacy collection classes

• These are obsolete (but not deprecated) Java collections, part of the original java.util. They synchronize each individual operation in a multithreaded program -- not what you want. (Generally, you want to synchronize a certain sequence of statements as opposed to a single statement.) The functionality of legacy collection classes is retrofitted into the latest Java API in a way that is best suitable for potentially thread-unsafe legacy code.

  
  Vector    // contains legacy methods no longer part of the collections framework
            // Vector is synchronized
            // For an alternative, see Collections.synchronizedList
  
  HashTable // similar to HashMap, but is synchronized
  
  Stack     // subclass of Vector that implements a stack
  
  

• Advice: do not use these legacy classes in your code! Instead,

  • ArrayList is the replacement of Vector

  • HashMap is the replacement of HashTable

  • Deque and ArrayDeque are replacements of Stack