How to iterate LinkedHashMap in Java?

19 Jan, 2021
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() MethodUsing entrySet() and Iterator
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));        }            }}
One -- 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 LinkesHashMap        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());    }}
LinkedHashMap entries : 
One=First element
Two=Second element
Three=Third element

Java-Collections
Java-LinkedHashMap
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