Iterate over a HashMap

In this post, we have seen how to add the element to HashMap. In this post, we will see how to iterate over a HashMap.

We can iterate over a HashMap by using two ways.

• For loop
• Iterator

It implements an interface Map.Entry to get the collection of key and value pair.

Syntax:

public static interface Map.Entry<K,V>

A map entry (key-value pair). The Map.entrySet method returns a collection-view of the map, whose elements are of this class. The only way to obtain a reference to a map entry is from the iterator of this collection-view.

It has following methods to read the key and value.

getKey() : Returns the key corresponding to this entry.

getValue(): Returns the value corresponding to this key entry.

Example with for loop:

import java.util.HashMap;
import java.util.Map;

public class HashMapEx {

	public static void  main(String[] args){
		
		HashMap<Integer,String> hm = new HashMap<Integer,String>();
		hm.put(1, "Mobile");
		hm.put(6, "TV");
		hm.put(10, "Laptop");
		hm.put(2, "Desktop");
		hm.put(15, "Tablet");
		
		for(Map.Entry m : hm.entrySet()){
			System.out.println(m.getKey()+"----"+m.getValue());
		}
	}
}

Output:

1—-Mobile
2—-Desktop
6—-TV
10—-Laptop
15—-Tablet

Example with Iterator:

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

public class HashMapEx {

	public static void  main(String[] args){
		
		HashMap<Integer,String> hm = new HashMap<Integer,String>();
		hm.put(1, "Mobile");
		hm.put(6, "TV");
		hm.put(10, "Laptop");
		hm.put(2, "Desktop");
		hm.put(15, "Tablet");
		
		Iterator iter = hm.entrySet().iterator();
		while(iter.hasNext()){
			Map.Entry m = (Map.Entry)iter.next();
			System.out.println(m.getKey()+"----"+m.getValue());
		}
	}
}

Output:

1—-Mobile
2—-Desktop
6—-TV
10—-Laptop
15—-Tablet