Java - Map Interface

Source Link:
https://www.tutorialspoint.com/java/java_map_interface.htm

Some Useful Methods:

void clear( )
Removes all key/value pairs from the invoking map.

boolean containsKey(Object k)
Returns true if the invoking map contains k as a key. Otherwise, returns false.

boolean containsValue(Object v)
Returns true if the map contains v as a value. Otherwise, returns false.

Object get(Object k)
Returns the value associated with the key k.

boolean isEmpty( )
Returns true if the invoking map is empty. Otherwise, returns false.

Set keySet( )
Returns a Set that contains the keys in the invoking map. This method provides a set-view of the keys in the invoking map.

Object put(Object k, Object v)
Puts an entry in the invoking map, overwriting any previous value associated with the key. The key and value are k and v, respectively. Returns null if the key did not already exist. Otherwise, the previous value linked to the key is returned.

Object remove(Object k)
Removes the entry whose key equals k.

int size( )
Returns the number of key/value pairs in the map.

Example: 
import java.util.*; 
public class CollectionsDemo {

   public static void main(String[] args) {
      Map m1 = new HashMap(); 
      m1.put("Zara", "8");
      m1.put("Mahnaz", "31");
      m1.put("Ayan", "12");
      m1.put("Daisy", "14");

      System.out.println();
      System.out.println(" Map Elements");
      System.out.print("\t" + m1);
   }
}

This will produce the following result − 
Map Elements

 {Daisy = 14, Ayan = 12, Zara = 8, Mahnaz = 31}