Java Proficiency: hashmap java

Showing posts with label hashmap java. Show all posts

Tuesday, 16 June 2015

How to get entry set from HashMap

import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

public class HashMapEntrySet {

    public static void main(String[] args) {

    Map<Integer,String> hm = new HashMap<Integer,String>();

    /*
    * Associates the specified value with the specified key in
       this map (optional operation). If the map previously
       contained a mapping for the key, the old value is
       replaced by the specified value
    */
        hm.put(1,"ankush");
        hm.put(2, "amit");
        hm.put(3,"shivam");
        hm.put(4,"ankit");
        hm.put(5, "yogesh");

        //print hashmap
        System.out.println("HashMap = "+hm);

        Set<Entry<Integer, String>> entry =hm.entrySet();

        for (Entry<Integer, String> entry2 : entry) {
            System.out.println(" Key = "+entry2.getKey()+" Value = "+entry2.getValue());
        }
    }

}

Output:

HashMap = {1=ankush, 2=amit, 3=shivam, 4=ankit, 5=yogesh}

Key = 1 Value = ankush

Key = 2 Value = amit

Key = 3 Value = shivam

Key = 4 Value = ankit

Key = 5 Value = yogesh

Sunday, 14 June 2015

How to get size of HashMap

import java.util.HashMap;
import java.util.Map;

public class HashMapKeyCount {

    public static void main(String[] args) {

        Map<Integer,String> hm = new HashMap<Integer,String>();

        /*
        * Associates the specified value with the specified key in
           this map (optional operation). If the map previously
           contained a mapping for the key, the old value is
           replaced by the specified value
        */
            hm.put(1,"ankush");
            hm.put(2, "amit");
            hm.put(3,"shivam");
            hm.put(4,"ankit");
            hm.put(5, "yogesh");

            //Returns the number of key-value mappings in this map

            System.out.println("HashMap size = "+hm.size());


        }

}

Output:

HashMap size = 5

How to get all keys of HashMap

import java.util.HashMap;
import java.util.Map;
import java.util.Set;

public class HashMapGetAllKeys {

        public static void main(String[] args) {

        Map<Integer,String> hm = new HashMap<Integer,String>();

        /*
        * Associates the specified value with the specified key in
           this map (optional operation). If the map previously
           contained a mapping for the key, the old value is
           replaced by the specified value
        */
            hm.put(1,"ankush");
            hm.put(2, "amit");
            hm.put(3,"shivam");
            hm.put(4,"ankit");
            hm.put(5, "yogesh");

            /*
            * Returns a Set view of the keys contained in this map
            */

            Set<Integer> keys =hm.keySet();

            for (Integer key : keys) {
                System.out.println(" key ="+key);
            }
        }

}

Output:

key =1

key =2

key =3

key =4

key =5

How to Search Value in HashMap Java

import java.util.HashMap;
import java.util.Map;

public class HashMapSearchValue {

   public static void main(String[] args) {

       Map<Integer,String> hm = new HashMap<Integer,String>();

       /*
       * Associates the specified value with the specified key in
           this map (optional operation). If the map previously
           contained a mapping for the key, the old value is
           replaced by the specified value
       */
            hm.put(1,"ankush");
           hm.put(2, "amit");
           hm.put(3,"shivam");
           hm.put(4,"ankit");
           hm.put(5, "yogesh");

           System.out.println(" value john ="+hm.containsValue("john"));
           System.out.println(" value amit ="+hm.containsValue("amit"));

           System.out.println(" value piyush ="+hm.containsValue("piyush"));
           System.out.println(" value shivam ="+hm.containsValue("shivam"));

       }

}

Output;

value john =false

value amit =true

value piyush =false

value shivam =true

How to Search key in HashMap Java

import java.util.HashMap;
import java.util.Map;

public class HashMapSearchKey {
    public static void main(String[] args) {

    Map<Integer,String> hm = new HashMap<Integer,String>();

    /*
    * Associates the specified value with the specified key in
       this map (optional operation). If the map previously
       contained a mapping for the key, the old value is
       replaced by the specified value
    */
        hm.put(1,"ankush");
        hm.put(2, "amit");
        hm.put(3,"shivam");
        hm.put(4,"ankit");
        hm.put(5, "yogesh");

        /*
        * Returns true if this map contains a
        * mapping for the specified key
        */

    System.out.println("key 1   ="+hm.containsKey(1));
    System.out.println("key 20 ="+hm.containsKey(20));
    System.out.println("key 9    ="+hm.containsKey(9));
    System.out.println("key 5   ="+ hm.containsKey(5));

    }
}

Output:
key 1   =true

key 20 =false

key 9    =false

key 5   =true

How to storing Java Object In HashMap

import java.util.HashMap;
import java.util.Map;
import java.util.Set;

public class HashMapStoreObject {

    public static void main(String[] args) {

        Map<Integer,Emp> hm = new HashMap<Integer, Emp>();

        hm.put(1, new Emp(100, "dk") );
        hm.put(2, new Emp(102, "kapil") );
        hm.put(3, new Emp(105, "anup") );
        hm.put(4, new Emp(205, "kapil") );
        hm.put(5, new Emp(110, "pk") );

           Set<Integer> keys = hm.keySet();

           for (Integer key : keys) {

               Emp emp = hm.get(key);
            System.out.println(" Id = "+emp.getId()+" name = "+emp.getName());
        }

    }

}

class Emp{

        private int id;
        private String name;

        public Emp(int id, String name) {
            this.id = id;
            this.name = name;
        }
        public int getId() {
            return id;
        }
        public void setId(int id) {
            this.id = id;
        }
        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }

}

Output:

Id = 100 name = dk

Id = 102 name = kapil

Id = 105 name = anup

Id = 205 name = kapil

Id = 110 name = pk

How to create HashMap In Java

import java.util.HashMap;
import java.util.Map;

public class CreateHashMap {

    public static void main(String[] args) {

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

    /*
    * Associates the specified value with the specified key in
       this map (optional operation). If the map previously
       contained a mapping for the key, the old value is
       replaced by the specified value
    */
        map.put(1,"ankush");
        map.put(2, "amit");
        map.put(3,"shivam");
        map.put(4,"ankit");
        map.put(5, "yogesh");

        //print hashmap
        System.out.println("HashMap = "+map);


    }

}

Output:

HashMap = {1=ankush, 2=amit, 3=shivam, 4=ankit, 5=yogesh}