Class AbstractMap

lib/java/util/AbstractMap.java:27–456

This class is an abstract implementation of the Map interface. This implementation does not support adding. A subclass must implement the abstract method entrySet(). @since 1.2

 * @since 1.2
 */
public abstract class AbstractMap<K, V> implements Map<K, V> {

    // Lazily initialized key set.
    Set<K> keySet;

    Collection<V> valuesCollection;

    /**
     * Constructs a new instance of this {@code AbstractMap}.
     */
    protected AbstractMap() {
        super();
    }

    /**
     * Removes all elements from this map, leaving it empty.
     * 
     * @throws UnsupportedOperationException
     *                if removing from this map is not supported.
     * @see #isEmpty()
     * @see #size()
     */
    public void clear() {
        entrySet().clear();
    }

    /**
     * Returns whether this map contains the specified key.
     * 
     * @param key
     *            the key to search for.
     * @return {@code true} if this map contains the specified key,
     *         {@code false} otherwise.
     */
    public boolean containsKey(Object key) {
        Iterator<Map.Entry<K, V>> it = entrySet().iterator();
        if (key != null) {
            while (it.hasNext()) {
                if (key.equals(it.next().getKey())) {
                    return true;
                }
            }
        } else {
            while (it.hasNext()) {
                if (it.next().getKey() == null) {
                    return true;
                }
            }
        }
        return false;
    }

    /**
     * Returns whether this map contains the specified value.
     * 
     * @param value
     *            the value to search for.
     * @return {@code true} if this map contains the specified value,