The Map Interface in java

A Mapis an object that maps keys to values. A map cannot contain duplicate keys: Each key can map to at most one value. The Map interface is shown below:

public interface Map {
    // Basic Operations
    Object put(Object key, Object value);
    Object get(Object key);
    Object remove(Object key);
    boolean containsKey(Object key);
    boolean containsValue(Object value);
    int size();    boolean isEmpty();
    // Bulk Operations
    void putAll(Map t);
    void clear();
    // Collection Views
    public Set keySet();
    public Collection values();
    public Set entrySet();
    // Interface for entrySet elements
    public interface Entry {
        Object getKey();
        Object getValue();
        Object setValue(Object value);
    }
}

The JDK contains two new general-purpose Map implementations. HashMap, which stores its entries in a hash table, is the best-performing implementation. TreeMap, which stores its entries in a red-black tree, guarantees the order of iteration. Also, Hashtablehas been retrofitted to implement Map. For more information on implementations, see the Implementations lesson.