HashMap

 //in hashmap duplicate value can we insert but , duplicate key not , all are unique.

import java.util.HashMap;

 public class Basic{

    public static void main(String[] args) {

    HashMap<Integer,String> map = new HashMap<>();

    map.put(78,"ved");

    map.put(99, "sneha");

    map.put(89, "tarun");

    map.put(90, "rajan");

    System.out.println(map);

    // size of map

    System.out.println(map.size());

    //  get(key)- gives the value of key

    System.out.println(map.get(90));

    // remove(key) - it delete key and pair both

    map.remove(89);

    System.out.println(map);

    // check value is exist or not

    System.out.println(map.containsValue("sneha"));

    // check key is exist or not

    System.out.println(map.containsKey(99));

    // we can update value- key remains same

    map.put(78, "dev");

    System.out.println(map);

    // value same bit chnage key

    map.put(9,"rajan");

    System.out.println(map);

    //keyset()

    for(int key:map.keySet()){

        String value=map.get(key);

        System.out.println(key+" "+value);

    }

    //values() - if values are same then also print

    for(String val:map.values()){

        System.out.println(val);

    }

    //entrySet()- gives pairs

    for(Object pair : map.entrySet()){

        System.out.println(pair);

    }

    }

}