Java Collection: LinkedHashMap

It is a Hash table and linked list implementation of the Map interface, where iteration order is predictable. It differs from HashMap in that it maintains a doubly-linked list.

Few important facts of LinkedHashMap are as follows:

1. It contains unique elements.
2. It is ordered collection.
3. It allows a null key, many null valeus.

---

Hierarchy of LinkedHashMap class

---

It extends HashMap and implements Map, Serializable and Cloneable interfaces in Java.

Source code of Item.java

package com.t4b.test; public class Item { String name; int id; double price; public Item(String name, int id, double price) { super(); this.name = name; this.id = id; this.price = price; } @Override public String toString() { return "Item [name=" + name + ", id=" + id + ", price=" + price + "]"; } }

Source code of TestMain.java

package com.t4b.test; import java.util.LinkedHashMap; import java.util.Map; public class TestMain { public static void main(String[] args) { LinkedHashMap<Integer, Item> map = new LinkedHashMap<Integer, Item>(); map.put(1, new Item("Apple", 1, 150.0)); map.put(2, new Item("Grape", 2, 250.0)); map.put(3, new Item("Mango", 3, 10)); map.put(2, new Item("Pine Apple", 4, 100)); for (Map.Entry item : map.entrySet()) { System.out.println(item.getKey() + " : " + item.getValue()); } } }

Happy Exploring!