Two different type indexed array in java

I need an array type for storing objects. But i need two types of access property like this:

array[0] >>> object1

array["a"] >>> object1

This means index 0 (an integer ) and开发者_Go百科 index a (a string) dereferences same object in the array. For storing objects, i think we need collections but how can i do access property that i mentioned above?

Create a map from the string keys to the numeric keys:

Map<String, Integer> keyMap = new HashMap<String, Integer>();
keyMap.put("a", o);
// etc

Then create a List of your objects, where MyObject is the value type:

List<MyObject> theList = new ArrayList<MyObject>();

Access by integer:

MyObject obj = theList.get(0);

Access by String

MyObject obj = theList.get(keyMap.get("a"));

This requires maintaining your key data structure, but allows for access of your values from one data structure.

You can encapsulte that is in a class, if you like:

public class IntAndStringMap<V> {
    private Map<String, Integer> keyMap;

    private List<V> theList;

    public IntAndStringMap() {
        keyMap = new HashMap<String, Integer>();
        theList = new ArrayList<V>();
    }

    public void put(int intKey, String stringKey, V value) {
        keyMap.put(stringKey, intKey);
        theList.ensureCapacity(intKey + 1); // ensure no IndexOutOfBoundsException
        theList.set(intKey, value);
    }

    public V get(int intKey) {
        return theList.get(intKey);
    }

    public V get(String stringKey) {
        return theList.get(keyMap.get(stringKey));
    }
}

Arrays only support indecies.

It appears you what to be able to look up an object by index and by key. In which case I suggest you have two collections. One for each type of lookup.

List<MyObject> list = new ArrayList<MyObject>();
Map<String, MyObject> map = new HashMapList<MyObject>():

// array[0] >>> object1
MyObject object0 = list.get(0);

// array["a"] >>> object1
MyObject objectA = map.get("a");