Java LinkedHashMap Example

• A LinkedHashMap contains values based on the key. It implements the Map interface and extends HashMap class.
• It contains only unique elements.
• It may have one null key and multiple null values.
• It is same as HashMap instead maintains insertion order.
• You can also create a LinkedHashMap that returns its elements in the order in which they were last accessed.

Hierarchy of LinkedHashMap class:
                               

Example of LinkedHashMap class:

import java.util.LinkedHashMap;

public class LinkedHashMapDemo {

public static void main(String[] args) {

LinkedHashMap<Integer, Integer> linkedMap = new LinkedHashMap<Integer, Integer>();

for (int i = 0; i < 10; i++) {

linkedMap.put(i, i);

}

System.out.println(linkedMap);

// Least-recently used order:

linkedMap = new LinkedHashMap<Integer, Integer>(16, 0.75f, true);

for (int i = 0; i < 10; i++) {

linkedMap.put(i, i);

}

System.out.println(linkedMap);

for (int i = 0; i < 7; i++) {

System.out.println(linkedMap.get(i));

}

System.out.println(linkedMap);

}

}

Output:

{0=0, 1=1, 2=2, 3=3, 4=4, 5=5, 6=6, 7=7, 8=8, 9=9}

{0=0, 1=1, 2=2, 3=3, 4=4, 5=5, 6=6, 7=7, 8=8, 9=9}

0

1

2

3

4

5

6

{7=7, 8=8, 9=9, 0=0, 1=1, 2=2, 3=3, 4=4, 5=5, 6=6}