HashMap Iteration

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January 18, 2017 by oneOokay

e.g. Map<String, List<String>> map = new HashMap<String, ArrayList<String>>();

如果只关心key的话就可以用for(T t : map.keySet())

for (String s : map.keySet())

如果只关心value的话就可以用for (T t: map.values())

for (List<List<String>> list : map.values())

如果要iterate全部,两种方法for 和 Iterator:

  • FOR:
    • for(Map.Entry<T,T> entry : map.entrySet())
    • for (Map.Entry<String, List<String>> entry : map.entrySet())
    • entry.getKey()
    • entry.getValue()
  • ITERATOR:
    • Iterator<Map.Entry<T,T>> entries = map.entrySet().iterator()
    • Iterator<Map.Entry<String, List<String>>> iter = map.entrySet().iterator()
    • while (iter.hasNext())
    • Map.Entry<T,T> entry = iter.next()
    • Map.Entry<String, List<String>> entry = iter.next();
    • entry.getKey()
    • entry.getValue()

 

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