How to use HashMAps in Java ?

HashMap can be used to store key-value pairs.

But sometimes you may want to store multiple values for the same key.

For example:

For Key A, you want to store - Apple, Aeroplane

For Key B, you want to store - Bat, Banana

For Key C, you want to store – Cat, Car

package com.skilledmonster.examples.util.map;

02.

03.import java.util.ArrayList;

04.import java.util.HashMap;

05.import java.util.List;

06.import java.util.Map;

07.

08./**

09.* HashMap - Single Key and Multiple Values using List

10.*

11.* @author Jagadeesh Motamarri

12.* @version 1.0

13.*/

14.public class SingleKeyMultipleValueUsingList {

15.

16.public static void main(String[] args) {

17.

18.// create map to store

19.Map> map = new HashMap>();

20.

21.// create list one and store values

22.List valSetOne = new ArrayList();

23.valSetOne.add("Apple");

24.valSetOne.add("Aeroplane");

25.

26.// create list two and store values

27.List valSetTwo = new ArrayList();

28.valSetTwo.add("Bat");

29.valSetTwo.add("Banana");

30.

31.// create list three and store values

32.List valSetThree = new ArrayList();

33.valSetThree.add("Cat");

34.valSetThree.add("Car");

35.

36.// put values into map

37.map.put("A", valSetOne);

38.map.put("B", valSetTwo);

39.map.put("C", valSetThree);

40.

41.// iterate and display values

42.System.out.println("Fetching Keys and corresponding [Multiple] Values n");

43.for (Map.Entry> entry : map.entrySet()) {

44.String key = entry.getKey();

45.List values = entry.getValue();

46.System.out.println("Key = " + key);

47.System.out.println("Values = " + values + "n");

48.}

49.}

50.}

1 Reply

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lakshmi priyaaka11y ago
HashMap can be used to store key-value pairs.
But sometimes you may want to store multiple values for the same key.
For example:
For Key A, you want to store - Apple, Aeroplane
For Key B, you want to store - Bat, Banana
For Key C, you want to store – Cat, Car
package com.skilledmonster.examples.util.map;
02.
03.import java.util.ArrayList;
04.import java.util.HashMap;
05.import java.util.List;
06.import java.util.Map;
07.
08./**
09.* HashMap - Single Key and Multiple Values using List
10.*
11.* @author Jagadeesh Motamarri
12.* @version 1.0
13.*/
14.public class SingleKeyMultipleValueUsingList {
15.
16.public static void main(String[] args) {
17.
18.// create map to store
19.Map> map = new HashMap>();
20.
21.// create list one and store values
22.List valSetOne = new ArrayList();
23.valSetOne.add("Apple");
24.valSetOne.add("Aeroplane");
25.
26.// create list two and store values
27.List valSetTwo = new ArrayList();
28.valSetTwo.add("Bat");
29.valSetTwo.add("Banana");
30.
31.// create list three and store values
32.List valSetThree = new ArrayList();
33.valSetThree.add("Cat");
34.valSetThree.add("Car");
35.
36.// put values into map
37.map.put("A", valSetOne);
38.map.put("B", valSetTwo);
39.map.put("C", valSetThree);
40.
41.// iterate and display values
42.System.out.println("Fetching Keys and corresponding [Multiple] Values n");
43.for (Map.Entry> entry : map.entrySet()) {
44.String key = entry.getKey();
45.List values = entry.getValue();
46.System.out.println("Key = " + key);
47.System.out.println("Values = " + values + "n");
48.}
49.}
50.}