LinkedHashMap Class

In this chapter you will learn:

1. How to use LinkedHashMap

Use LinkedHashMap

LinkedHashMap extends HashMap. It maintains a linked list of the entries in the map, in the order in which they were inserted. This allows insertion-order iteration over the map.

LinkedHashMap is a generic class that has this declaration:

• K specifies the type of keys
• V specifies the type of values.

LinkedHashMap adds only one method to those defined by HashMap. This method is removeEldestEntry( ) and it is shown here:

This method is called by put( ) and putAll( ). The oldest entry is passed in e.

import java.util.LinkedHashMap;
/*ja v  a2 s  .com*/
public class Main {

  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);
  }
}

The code above generates the following result.

Next chapter...

What you will learn in the next chapter:

1. How to use IdentityHashMap
2. What are the difference between IdentityHashMap and HashMap

Map interface

Map element adding

Map.Entry class

Map key

Map value

Map key/value search

Map delete/remove

Map comparison

HashMap Class

HashMap search

HashMap clone

TreeMap

TreeMap key

TreeMap head sub map

TreeMap tail sub map

TreeMap sub map

NavigableMap

NavigableMap key

NavigableMap key-value pair

LinkedHashMap Class

IdentityHashMap

SortedMap