Map Interface

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

Roll Number	Name
123	Krishna
124	Ram
125	Anil
126	Kiran

In the above table, Roll number is the key, which maps to student name. I.e, Roll Number 123 maps to the student name Krishna, 126 maps to the student name Kiran.

public interface Map<K,V> {

    int size();
    boolean isEmpty(); 
    boolean containsKey(Object key);
    boolean containsValue(Object value);
    V get(Object key);
    V put(K key, V value);
    V remove(Object key);
    void putAll(Map<? extends K, ? extends V> m);
    void clear();
    Set<K> keySet();
    Collection<V> values();
    Set<Map.Entry<K, V>> entrySet();
  
    interface Entry<K,V> { 
        K getKey(); 
        V getValue();
        V setValue(V value);
        boolean equals(Object o);
        int hashCode();
    }
  
    boolean equals(Object o);
    int hashCode();
}

HashMap, TreeMap, and LinkedHashMap are the General Implementations of the Map interface.

Example

import java.util.*;
class MapEx{
  public static void main(String args[]){
    Map<Integer, String> studentTable = new TreeMap<> ();
  
  /* Add Student details */
  studentTable.put(123, "Krishna");
  studentTable.put(124, "Ram");
  studentTable.put(125, "Anil");
  studentTable.put(126, "Kiran");
  
  System.out.println("Data in Student Map is");
  System.out.println(studentTable);
  }
}

Output

Data in Student Map is
{123=Krishna, 124=Ram, 125=Anil, 126=Kiran

Classes That timplements Map interface are

AbstractMap, Attributes, AuthProvider, ConcurrentHashMap,

ConcurrentSkipListMap, EnumMap, HashMap, Hashtable, IdentityHashMap, LinkedHashMap, PrinterStateReasons, Properties, Provider, RenderingHints, SimpleBindings, TabularDataSupport, TreeMap, UIDefaults, WeakHashMap

Prevoius                                                 Next                                                 Home