A tutorial on HashMap. Maps are data collections that function like lookup tables; basically you can store objects via “keys” (names, IDs, or even complex objects) and quickly retrieve them without having to look through an entire list.

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Code For This Tutorial

App.java:

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

public class App {


	public static void main(String[] args) {

		HashMap<Integer, String> map = new HashMap<Integer, String>();
		
		map.put(5, "Five");
		map.put(8, "Eight");
		map.put(6, "Six");
		map.put(4, "Four");
		map.put(2, "Two");
		
		String text = map.get(6);
		
		System.out.println(text);
		
		for(Map.Entry<Integer, String> entry: map.entrySet()) {
			int key = entry.getKey();
			String value = entry.getValue();
			
			System.out.println(key + ": " + value);
		}
		
	}

}

Six
2: Two
4: Four
5: Five
6: Six
8: Eight

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