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ArrayMap.javaAPI DocAndroid 5.1 API7714Thu Mar 12 22:22:56 GMT 2015android.support.v4.util

ArrayMap

public class ArrayMap extends SimpleArrayMap implements Map
ArrayMap is a generic key->value mapping data structure that is designed to be more memory efficient than a traditional {@link java.util.HashMap}, this implementation is a version of the platform's {@link android.util.ArrayMap} that can be used on older versions of the platform. It keeps its mappings in an array data structure -- an integer array of hash codes for each item, and an Object array of the key/value pairs. This allows it to avoid having to create an extra object for every entry put in to the map, and it also tries to control the growth of the size of these arrays more aggressively (since growing them only requires copying the entries in the array, not rebuilding a hash map).

If you don't need the standard Java container APIs provided here (iterators etc), consider using {@link SimpleArrayMap} instead.

Note that this implementation is not intended to be appropriate for data structures that may contain large numbers of items. It is generally slower than a traditional HashMap, since lookups require a binary search and adds and removes require inserting and deleting entries in the array. For containers holding up to hundreds of items, the performance difference is not significant, less than 50%.

Because this container is intended to better balance memory use, unlike most other standard Java containers it will shrink its array as items are removed from it. Currently you have no control over this shrinking -- if you set a capacity and then remove an item, it may reduce the capacity to better match the current size. In the future an explicit call to set the capacity should turn off this aggressive shrinking behavior.

Fields Summary
MapCollections
mCollections
Constructors Summary
public ArrayMap()

        super();
public ArrayMap(int capacity)
Create a new ArrayMap with a given initial capacity.

        super(capacity);
public ArrayMap(SimpleArrayMap map)
Create a new ArrayMap with the mappings from the given ArrayMap.

        super(map);
Methods Summary
public booleancontainsAll(java.util.Collection collection)
Determine if the array map contains all of the keys in the given collection.

param
collection The collection whose contents are to be checked against.
return
Returns true if this array map contains a key for every entry in collection, else returns false.

        return MapCollections.containsAllHelper(this, collection);
public java.util.SetentrySet()
Return a {@link java.util.Set} for iterating over and interacting with all mappings in the array map.

Note: this is a very inefficient way to access the array contents, it requires generating a number of temporary objects.

Note:

the semantics of this Set are subtly different than that of a {@link java.util.HashMap}: most important, the {@link java.util.Map.Entry Map.Entry} object returned by its iterator is a single object that exists for the entire iterator, so you can not hold on to it after calling {@link java.util.Iterator#next() Iterator.next}.

        return getCollection().getEntrySet();
private MapCollectionsgetCollection()

        if (mCollections == null) {
            mCollections = new MapCollections<K, V>() {
                @Override
                protected int colGetSize() {
                    return mSize;
                }

                @Override
                protected Object colGetEntry(int index, int offset) {
                    return mArray[(index<<1) + offset];
                }

                @Override
                protected int colIndexOfKey(Object key) {
                    return indexOfKey(key);
                }

                @Override
                protected int colIndexOfValue(Object value) {
                    return indexOfValue(value);
                }

                @Override
                protected Map<K, V> colGetMap() {
                    return ArrayMap.this;
                }

                @Override
                protected void colPut(K key, V value) {
                    put(key, value);
                }

                @Override
                protected V colSetValue(int index, V value) {
                    return setValueAt(index, value);
                }

                @Override
                protected void colRemoveAt(int index) {
                    removeAt(index);
                }

                @Override
                protected void colClear() {
                    clear();
                }
            };
        }
        return mCollections;
public java.util.SetkeySet()
Return a {@link java.util.Set} for iterating over and interacting with all keys in the array map.

Note: this is a fairly inefficient way to access the array contents, it requires generating a number of temporary objects.

        return getCollection().getKeySet();
public voidputAll(java.util.Map map)
Perform a {@link #put(Object, Object)} of all key/value pairs in map

param
map The map whose contents are to be retrieved.

        ensureCapacity(mSize + map.size());
        for (Map.Entry<? extends K, ? extends V> entry : map.entrySet()) {
            put(entry.getKey(), entry.getValue());
        }
public booleanremoveAll(java.util.Collection collection)
Remove all keys in the array map that exist in the given collection.

param
collection The collection whose contents are to be used to remove keys.
return
Returns true if any keys were removed from the array map, else false.

        return MapCollections.removeAllHelper(this, collection);
public booleanretainAll(java.util.Collection collection)
Remove all keys in the array map that do not exist in the given collection.

param
collection The collection whose contents are to be used to determine which keys to keep.
return
Returns true if any keys were removed from the array map, else false.

        return MapCollections.retainAllHelper(this, collection);
public java.util.Collectionvalues()
Return a {@link java.util.Collection} for iterating over and interacting with all values in the array map.

Note: this is a fairly inefficient way to access the array contents, it requires generating a number of temporary objects.

        return getCollection().getValues();