JAVA - How To Use HashMap In Java With Iterator

                                                                                                                                                            

In this java Collection tutorial we will see How To Use A HashMap With Iterator In Java NetBeans

Source Code:

package JavaDB_001;

import java.util.*;

public class Work {

    public static void main(String[] args){

        //create a HashMap

        //Key is String 

        //value is Integer

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

       

       //filling the HashMap with put method

       employer.put("employer 1", 34);

       employer.put("employer 2", 43);

       employer.put("employer 3", 36);

       employer.put("employer 5", 55);

       employer.put("employer 6", 29);

       employer.put("employer 7", 27);

       employer.put("employer 8", 30);

       employer.put("employer 9", 51);

       

       //displaying only the key of the hashmap

       System.out.println("_______Key_______");

         Iterator<String> itName = employer.keySet().iterator();

            while(itName.hasNext())

             System.out.println(itName.next());

       

       //displaying only the value of the hashmap

       System.out.println("_______Value_______");

        Iterator<Integer> itAge = employer.values().iterator();

          while(itAge.hasNext())

            System.out.println(itAge.next());

       

      //displaying the key and the value of the hashmap

       System.out.println("_______Key_And_Value_______");  

         Iterator<String> itname = employer.keySet().iterator();

            while(itname.hasNext()){

                String s = itname.next();

              System.out.println(itname.next()+" -*- "+employer.get(s));

           }

    }

       

}

///////////////////////////OUTPUT:

_______Key_______

employer 9

employer 5

employer 6

employer 7

employer 8

employer 1

employer 2

employer 3

_______Value_______

51

55

29

27

30

34

43

36

_______Key_And_Value_______

employer 9 -*- 51

employer 5 -*- 55

employer 6 -*- 29

employer 7 -*- 27

employer 8 -*- 30

employer 1 -*- 34

employer 2 -*- 43

employer 3 -*- 36

See Also: How To Use HashMap In Java

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JAVA - How To Use HashMap In Java

JAVA - How To Use HashMap In Java NetBeans

                                                                                                                                                            

In this java Collection Code we will see How To Use A HashMap In Java NetBeans
With Some Java HashMap Example of Methodes.

1: how to create a HashMap 

2: how to dispaly data from it

3: how to remove an element

4: how to clear all elements from it
and more........

Source Code:

package JavaDB_001;

import java.util.*;

public class Work {

    public static void main(String[] args){

        //create a HashMap

        //Key is String 

        //value is Integer

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

       

       //filling the HashMap with put method

       employer.put("employer 1", 34);

       employer.put("employer 2", 43);

       employer.put("employer 3", 36);

       employer.put("employer 5", 55);

       employer.put("employer 6", 29);

       employer.put("employer 7", 27);

       employer.put("employer 8", 30);

       employer.put("employer 9", 51);

       

       //displaying only the key of the hashmap

       Set<String> EmployerName = employer.keySet();

       System.out.println("_______Key_______");

       for(String s: EmployerName)

           System.out.println(s);

       

       //displaying only the value of the hashmap

       Collection<Integer> Age = employer.values();

       System.out.println("_______Value_______");

       for(Integer i : Age)

           System.out.println(i);

       

      //displaying the key and the value of the hashmap

       System.out.println("_______Key_And_Value_______");

      Set<String> EmpName = employer.keySet();

       for(String s: EmpName)

           System.out.println("Key => ["+s +"] Value => ["+employer.get(s)+"]");

    }

       

}

///////////////////////////OUTPUT:
_______Key_______
employer 9
employer 5
employer 6
employer 7
employer 8
employer 1
employer 2
employer 3
_______Value_______
51
55
29
27
30
34
43
36
_______Key_And_Value_______
Key => [employer 9] Value => [51]
Key => [employer 5] Value => [55]
Key => [employer 6] Value => [29]
Key => [employer 7] Value => [27]
Key => [employer 8] Value => [30]
Key => [employer 1] Value => [34]
Key => [employer 2] Value => [43]
Key => [employer 3] Value => [36]


Another Source Code:

package javaapp;

import java.util.ArrayList;
import java.util.HashMap;


public class Work {
    public static void main(String[] args){
        HashMap<Integer, String> map = new HashMap<Integer, String>();
        map.put(10, "A");
        map.put(20, "B");
        map.put(30, "C");
        map.put(40, "D");
        map.put(50, "E");
        map.put(60, "F");
        
        printData(map);
        
        // delete an elemnt from the hashmap
        map.remove(60);
        printData(map);
        System.out.println("");
        System.out.println(map);
        
        map.replace(10, "Z");
        System.out.println(map);
        
        // see if the map contains a value
        boolean statVal = map.containsValue("Z");
        System.out.println(statVal);
        
        // see if the map contains a key
        boolean statKey = map.containsKey(40);
        System.out.println(statKey);
        
        // get value using his key
        String val = map.get(100);
        System.out.println(val);
        
        // check if the map is empty
        boolean isEmpty = map.isEmpty();
        System.out.println(isEmpty);

        // insert tvalues from hashmap to arraylist
        ArrayList<String> values = new ArrayList<String>(map.values());
        System.out.println("Values: "+values); 
        
        // create another hashmap
        HashMap<Integer, String> map2 = new HashMap<Integer, String>();
        map2.put(100,"MAP2-1");
        map2.put(200,"MAP2-2");
        map2.put(300,"MAP2-3");
        
        // insert a map in another map
        map.putAll(map2);
        printData(map);
        
       // clone the hashmap 
       Object obj = map.clone();
       System.out.println(obj);
       
       /*
       If the specified key is not associated with a value
       or the value is null associates it with the given value 
       in this example the key is 111 and value is null
       */
       map.put(111, null);
       map.putIfAbsent(111, "NewValue");
       System.out.println(map);
       
        // get the HashMap Size
        int mapSize = map.size();
        System.out.println(mapSize);
        
        // clear all elements from the hashmap
        map.clear();
        mapSize = map.size();
        System.out.println(mapSize);
        System.out.println("The HashMap Is Clear: "+map);
        System.out.println("The HashMap is Empty Now = "+map.isEmpty());
        
    }
    
    // cretate a function to print data from the hashmap 
    public static void printData(HashMap<Integer,String> list){
        for(Integer i : list.keySet()){
            System.out.println("Key: "+i+" Value: "+list.get(i));
        }
        System.out.println("-----------------------");
    }
}

//OUTPUT:

Key: 50 Value: E
Key: 20 Value: B
Key: 40 Value: D
Key: 10 Value: A
Key: 60 Value: F
Key: 30 Value: C
-----------------------
Key: 50 Value: E
Key: 20 Value: B
Key: 40 Value: D
Key: 10 Value: A
Key: 30 Value: C
-----------------------

{50=E, 20=B, 40=D, 10=A, 30=C}
{50=E, 20=B, 40=D, 10=Z, 30=C}
true
true
null
false
Values: [E, B, D, Z, C]
Key: 50 Value: E
Key: 20 Value: B
Key: 100 Value: MAP2-1
Key: 40 Value: D
Key: 200 Value: MAP2-2
Key: 10 Value: Z
Key: 300 Value: MAP2-3
Key: 30 Value: C
-----------------------
{50=E, 20=B, 100=MAP2-1, 40=D, 200=MAP2-2, 10=Z, 300=MAP2-3, 30=C}
{50=E, 20=B, 100=MAP2-1, 40=D, 200=MAP2-2, 10=Z, 300=MAP2-3, 30=C, 111=NewValue}
9
0
The HashMap Is Clear: {}

The HashMap is Empty Now = true



See Also : HashMap In Java With Iterator

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