Searching Key and finding value associated with it in a HashTable

 

import java.util.Hashtable;

import java.util.Scanner;

public class FindSizeAndKey {

public static void main(String[] args) {

Hashtable<Integer, String> ht = new Hashtable<>();

//adding element to our HashTable

ht.put(1, "Vidya");

ht.put(2, "Sambhavna");

ht.put(3, "Tina");

ht.put(4, "Gravit");

ht.put(5, "Anmol");

ht.put(6, "Veer");

//finding size of our HashTable

System.out.println("Size of Table is = " + ht.size());

//checking if a key is present in the table or not

Scanner sc = new Scanner(System.in);

System.out.println("Enter the key you want to find");

int key = sc.nextInt();

if (ht.containsKey(key)) {

String value = ht.get(key);

System.out.println(

"The value stored at key " + key + " is --->>> " + value

);

}

}

}

Setting initial capacity and load factor of a HashTable

 

import java.util.Hashtable;

public class HashTableInitialCapacity {

public static void main(String[] args) {

//Creating a HashTable with Initial Capacity

//Default load factor is .75;

Hashtable<Integer, String> ht = new Hashtable<>(5);

//adding element to our HashTable

ht.put(1, "Vidya");

ht.put(2, "Sambhavna");

ht.put(3, "Tina");

ht.put(4, "Gravit");

ht.put(5, "Anmol");

ht.put(6, "Veer");

//finding size of our HashTable

System.out.println(ht.size());

Hashtable<Integer, String> ht1 = new Hashtable<>(4, .90f);

ht1.put(9, "Rehana");

ht1.put(10, "Ritik");

ht1.put(11, "Viresha");

System.out.println("Mapping of ht " + ht);

System.out.println("Mapping of ht1 " + ht1);

}

}

Adding Element to a HashTable

 

import java.util.Hashtable;

import java.util.Iterator;

public class HashTableDemo {

public static void main(String[] args) {

//creating hashTable

Hashtable<Integer, String> ht = new Hashtable<>();

//Adding element to our HashTable

ht.put(1, "Vidya");

ht.put(2, "Sambhavna");

ht.put(3, "Tina");

ht.put(4, "Gravit");

ht.put(5, "Anmol");

Iterator<Integer> itr = ht.keySet().iterator();

//cant perform any manupulation after taking iterator out

// ht.put(6, "Kiran");

while (itr.hasNext()) {

Integer key = itr.next();

String value = ht.get(key);

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

}

}

}

Finding size of a HashMap

 

import java.util.HashMap;

import java.util.Iterator;

import java.util.Map;

public class HashMapSize {

public static void main(String[] args) {

//Creating HashMap;

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

//Putting element

hm.put(1, "Naidu");

hm.put(3, "Rohilla");

hm.put(5, "Vijay");

hm.put(2, "Rahul");

hm.put(4, "Ramakesh");

hm.put(6, "Sudeep");

hm.putIfAbsent(7, "Badrabahu");

System.out.println(hm.size());

}

}

Combining elements of two HashMap using in-built method putAll()

 

import java.util.HashMap;

import java.util.Iterator;

import java.util.Map;

public class HashMapPutAll {

public static void main(String[] args) {

//Creating HashMap;

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

//Putting element

hm.put(1, "Naidu");

hm.put(3, "Rohilla");

hm.put(5, "Vijay");

hm.put(2, "Rahul");

hm.put(4, "Ramakesh");

hm.put(6, "Sudeep");

hm.putIfAbsent(7, "Badrabahu");

HashMap<Integer,String> hm1 = new HashMap<>();

//must value must not be same to use putAll() method

hm1.put(8,"language");

hm1.put(9,"java");

hm1.put(10,"bike");

hm.putAll(hm1);

System.out.println(hm);

}

}

Replacing element in a HashMap

 

import java.util.HashMap;

import java.util.Iterator;

import java.util.Map;

public class HashMapReplace {

public static void main(String[] args) {

//Creating HashMap;

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

//Putting element

hm.put(1, "Naidu");

hm.put(3, "Rohilla");

hm.put(5, "Vijay");

hm.put(2, "Rahul");

hm.put(4, "Ramakesh");

hm.put(6, "Sudeep");

//Storing null value

hm.put(null, null);

hm.replace(1, "Sourav");

//as key is not present in the map, no action will be performed

hm.replace(7, "Virender");

System.out.println(hm);

}

}

Deleting element from HashMap using built-in method remove()

 

import java.util.HashMap;

import java.util.Iterator;

import java.util.Map;

public class HashMapRemove {

public static void main(String[] args) {

//Creating HashMap;

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

//Putting element

hm.put(1, "Naidu");

hm.put(3, "Rohilla");

hm.put(5, "Vijay");

hm.put(2, "Rahul");

hm.put(4, "Ramakesh");

hm.put(6, "Sudeep");

//Storing null value

hm.put(null, null);

hm.remove(5);

System.out.println(hm);

hm.remove(6, "Sudeep");

System.out.println(hm);

//key and value doesn't match, no operation will be performed

hm.remove(4, "Rahul");

System.out.println(hm);

}

}

Getting specific element from HashMap Using built-in method get()

 

import java.util.HashMap;

import java.util.Iterator;

import java.util.Map;

public class HashMapGetDemo {

public static void main(String[] args) {

//Creating HashMap;

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

//Putting element

hm.put(1, "Naidu");

hm.put(3, "Rohilla");

hm.put(5, "Vijay");

hm.put(2, "Rahul");

hm.put(4, "Ramakesh");

hm.put(6, "Sudeep");

//Storing null value

hm.put(null, null);

System.out.println(hm.get(5));

System.out.println(hm.get("Sudeep")); //returns null

System.out.println(hm.get(4));

}

}

Iterating HashMap Using ForEach(action) loop

import java.util.HashMap;

import java.util.Iterator;

import java.util.Map;

public class HashMapIteration4 {

public static void main(String[] args) {

//Creating HashMap;

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

//Putting element

hm.put(1, "Naidu");

hm.put(3, "Rohilla");

hm.put(5, "Vijay");

hm.put(2, "Rahul");

hm.put(4, "Ramakesh");

hm.put(6, "Sudeep");

//Storing null value

hm.put(null, null);

System.out.println("Iterating HashMap Using ForEach(action) loop");

hm.forEach(

(k, v) -> System.out.println("key = " + k + "," + "Value = " + v)

);

}

}

Iterating over hashmap using Iterator

 

import java.util.HashMap;

import java.util.Iterator;

import java.util.Map;

public class HashMapIteration3 {

public static void main(String[] args) {

//Creating HashMap;

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

//Putting element

hm.put(1, "Naidu");

hm.put(3, "Rohilla");

hm.put(5, "Vijay");

hm.put(2, "Rahul");

hm.put(4, "Ramakesh");

hm.put(6, "Sudeep");

//Storing null value

hm.put(null, null);

System.out.println("Iterating HashMap Using For each loop");

Iterator<Map.Entry<Integer,String>> itr = hm.entrySet().iterator();

while (itr.hasNext()) {

HashMap.Entry<Integer, String> entry = itr.next();

System.out.println(

"Key = " + entry.getKey() + " " + "Value = " + entry.getValue()

);

}

}

}