The LinkedHashMap is just like HashMap with an additional feature of maintaining an order of elements inserted into it. LinkedHashMap in Java is an implementation that combines HashTable and LinkedList implementation. It implements the Map interface. The key-value pairs of LinkedHashMap have a predictable order of iteration.
We can use the entrySet() method to print all mappings of the LinkedHashMap which returns all the entries contained in the LinkedHashMap object.
Example:
Input: Key = ["1st-year", "2nd-year", "4th-year"] Value = ["neveropen DSA course", "DBMS course", "Interview prep"] Output: 1st-year : neveropen DSA course 2nd-year : DBMS course 4th-year : Interview prep Input: Key = [3, 2, 1] Value = ["geeks", "for", "geeks"] Output: 3 : geeks 2 : for 1 : geeks
LinkedHashMap(): This is used to construct a default LinkedHashMap constructor.
LinkedHashMap<K, V> l_map = new LinkedHashMap<K, V>(); Here, K is the key Object type and V is the value Object type.
Method’s Syntax:
l_map.entrySet()
Returns: This method returns a Key-Value pair in an ordered manner.
Example 1: The following implementation demonstrates all mappings of the LinkedHashMap using entrySet() method in the key-value pair.
Java
// Java program to Print all // Mappings of the LinkedHashMapimport java.util.*; class IteratingOverLinkedHashMap { public static void main(String args[]) { // create an instance of LinkedHashMap LinkedHashMap<String, String> l_map = new LinkedHashMap<String, String>(); // Add mappings using put method l_map.put("1st-year", "neveropen DSA course"); l_map.put("2nd-year", "DBMS course"); l_map.put("4th-year", "Interview prep"); // retrieve the key-value pairs as set using // entrySet & print each entry for (Map.Entry<String, String> mapElement : l_map.entrySet()) { // Finding the key String key = mapElement.getKey(); // Finding the value String value = mapElement.getValue(); // print the key : value pair System.out.println(key + " : " + value); } }} |
1st-year : neveropen DSA course 2nd-year : DBMS course 4th-year : Interview prep
Example 2: Another method to print a Key-Value pair is a toString() method of the LinkedHashMap class.
Java
// Java program to Print all // Mappings of the LinkedHashMapimport java.util.*; class IteratingOverLinkedHashMap { public static void main(String args[]) { // create an instance of LinkedHashMap LinkedHashMap<Integer, String> l_map = new LinkedHashMap<Integer, String>(); LinkedHashMap<Integer, Integer> r_map = new LinkedHashMap<Integer, Integer>(); // Add mappings using put method l_map.put(3, "geeks"); l_map.put(2, "for"); l_map.put(1, "geeks"); // Add mappings using put method r_map.put(3, 1); r_map.put(2, 2); r_map.put(1, 3); // The toString method returns all mappings of // map where keys and values are separated by a =, // each mapping is separated by a comma and all // mappings are enclosed in { and }. System.out.println(r_map); // retrieve the key-value pairs as set using // entrySet & print each mapElement for (Map.Entry<Integer, String> mapElement : l_map.entrySet()) { // Finding the key Integer key = mapElement.getKey(); // Finding the value String value = mapElement.getValue(); // print the key : value pair System.out.println(key + " : " + value); } }} |
{3=1, 2=2, 1=3}
3 : geeks
2 : for
1 : geeks
Time Complexity: O(n), where n is the number of mappings.
