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how to iterate linkedhashmap in java?


LinkedHashMap

LinkedHashMap extends HashMap class and implements the Map interface. It contains the elements in key-value pair form. It maintains insertion order for its elements. It not allowed duplicate key. A LinkedHashMap can have only one null key and multiple null values.

We can use iterator interface. It is a universal iterator as we can apply it to any Collection object. It provides the functionality of read and remove operations. Collection interface provides iterator() method to get the Iterator object. Iterator interface have following to methods to iterate collection objects.

hasNext(): It returns true if the iteration has more elements.
next(): It returns the next element in the iteration.

Example

package com.codesjava;
 
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;
 
public class Test {
	public static void main(String args[]){
		LinkedHashMap<Integer, String> linkedHashMap = 
				new LinkedHashMap<Integer, String>();
 
		//Add objects to the HashSet.
		linkedHashMap.put(4, "Roxy");
		linkedHashMap.put(2, "Sunil");
		linkedHashMap.put(5, "Sandy");
		linkedHashMap.put(1, "Munish");
		linkedHashMap.put(3, "Pardeep");
 
		//Print the LinkedHashMap object.
		System.out.println("LinkedHashMap elements:");
		System.out.println(linkedHashMap);
 
		//Get iterator
		Set set=linkedHashMap.entrySet();  
		Iterator iterator=set.iterator();  
 
		//Print the LinkedHashMap elements using iterator.
		System.out.println("LinkedHashMap elements " +
				"using iterator:");
		while(iterator.hasNext()){
		   Map.Entry mapEntry=(Map.Entry)iterator.next();  
		   System.out.println("Key: " + mapEntry.getKey() + 
				   ", Value: " + mapEntry.getValue());  
		}  
	}
}

Output

LinkedHashMap elements:
{4=Roxy, 2=Sunil, 5=Sandy, 1=Munish, 3=Pardeep}
LinkedHashMap elements using iterator:
Key: 4, Value: Roxy
Key: 2, Value: Sunil
Key: 5, Value: Sandy
Key: 1, Value: Munish
Key: 3, Value: Pardeep


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