How to iterate LinkedHashMap in Java?
Last Updated : 25 Apr, 2023
LinkedHashMap class extends HashMap and 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. That is, when iterating a LinkedHashMap, the elements will be returned in the order in which they were inserted.
There are basically two ways to iterate over LinkedHashMap:
- Using keySet() and get() Method
- Using entrySet() and Iterator
Method 1: Iterating LinkedHashMap using keySet() and get() Method
Syntax:
linked_hash_map.keySet()
Parameters: The method does not take any parameter.
Return Value: The method returns a set having the keys of the LinkedHashMap.
- Through keySet() method we will obtain a set having keys of the map.
- And then after running a loop over this set, we can obtain each key and its value using get() method.
Java // Java Program to iterate through LinkedHashMap using // keySet() and get() Method import java.util.LinkedHashMap; import java.util.Set; public class GFG { public static void main(String a[]) { // making the object of LinkedHashMap LinkedHashMap<String, String> linkedHashMap = new LinkedHashMap<String, String>(); // adding the elements in linkedHashMap linkedHashMap.put("One", "First element"); linkedHashMap.put("Two", "Second element"); linkedHashMap.put("Three", "Third element"); Set<String> keys = linkedHashMap.keySet(); // printing the elements of LinkedHashMap for (String key : keys) { System.out.println(key + " -- " + linkedHashMap.get(key)); } } } OutputOne -- First element Two -- Second element Three -- Third element
Method 2: Iterating LinkedHashMap using entrySet() and Iterator
Syntax:
Linkedhash_map.entrySet()
Parameters: The method does not take any parameter.
Return Value: The method returns a set having same elements as the LinkedHashMap.
Java // Java Program to iterate over linkedHashMap using // entrySet() and iterator import java.util.Iterator; import java.util.LinkedHashMap; import java.util.Set; public class GFG { public static void main(String[] args) { // Create a LinkedHashMap and populate it with // elements LinkedHashMap<String, String> linkedHashMap = new LinkedHashMap<String, String>(); // adding the elements to the linkedHashMap linkedHashMap.put("One", "First element"); linkedHashMap.put("Two", "Second element"); linkedHashMap.put("Three", "Third element"); // Get a set of all the entries (key - value pairs) // contained in the LinkedHashMap Set entrySet = linkedHashMap.entrySet(); // Obtain an Iterator for the entries Set Iterator it = entrySet.iterator(); // Iterate through LinkedHashMap entries System.out.println("LinkedHashMap entries : "); while (it.hasNext()) // iterating over each element using it.next() // method System.out.println(it.next()); } } OutputLinkedHashMap entries : One=First element Two=Second element Three=Third element