How to Get a Set of Keys in HashMap in Java

In this example we will show how to get a Set of keys contained in HashMap with keySet method of java HashMap class.

Source Code

package com.beginner.examples;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Set;

public class GetHashMapKeyExample {

	
	public static void main(String[] args) {
		
		//Create a HashMap object
		HashMap map = new HashMap();
		
		//Put Key-value
		map.put("1", "Jan");
		map.put("2", "Feb");
		map.put("3", "Mar");
		map.put("4", "Apr");
		map.put("5", "May");
		
		//Gets a collection of all the keys in the HashMap
		Set indexSet = map.keySet();
		
		//Iterate through the collection using an iterator
		Iterator iterator = indexSet.iterator();
		
		while(iterator.hasNext())
		{
			String key = iterator.next();
			String value = map.get(key);
			System.out.println(key+"::"+value);
		}

	}

}

Output:

3::Mar
2::Feb
1::b
5::May
4::Apr

References

Imported packages in Java documentation:

Set
HashMap
Iterator