which data structure should I use in java to store duplicate values?

Which is the best data structure to store duplicate values in java? And how easy is to retrieve values from it!?

thanks EDIT #1 I am reading contents from 1000 files, and I want to put each files content as tokens in some data structure. I used Hashtable but i am not able to view many words when I am doing that. thats why I want a data structure which can 开发者_运维问答store the duplicate values.

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For just storing simple values, you should use an implementation of the List<E> interface.

To get data from a List<E> you can do the following:

list.get(index); // will get data at a given index
// or you can iterate over all of the items in the list
for(E item: list) {
    // use E
}

Depending on your use either an ArrayList<E> or LinkedList<E> will do what you need.

Another option would be a Map<K, V> (it's implementation HashMap). This will allow you to save duplicate values under unique keys.

You can get values out of a Map<K,V> in the following ways:

map.get(someKey); // will retrieve the value associated with a key
// or you can iterate through all of the entries in a map like so:
for(Entry<K,V> entry: map.entrySet()){
    // use entry
}

Response to your edit:

You may want to use a Map<String, List<String>> where the key is the name of the file, and the value is a list of the words in the file.

Your code may look like this:

Map<String, List<String>> data = new HashMap<String, List<String>>();
for(File f: files) {
    List<String> words = new ArrayList<String();
    data.put(f.getName(), words);
    Scanner s = new Scanner(f);
    while(s.hasNext()) {
        words.add(s.next());
    }
}

At the end of this snipit, data will be filled with lists of words from each file.

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theres lack of info to properly answer this qn.. but anyway, hashmaps could do the trick. retrieval of values can be done in constant time on average..

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You should use List<E> but you should implement a int[] getDuplicateValuesIndexes(String value) method and a int getCount(String value). These will be useful because in List<E> implementations, there are nothing to treat duplicate values as they store just values of any kind.

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Any java.util.Collection that does not implement the Set interface. Probably you'll want something that implements a List.

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Use Arrays, to get value use index (I know its incomplete answer, but so is the question)