Use of Map interface and implementation class HashMap

package myPro1;

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

//The use of the Map interface and the implementation class HashMap
//The difference between Map interface and Set and List is that it does not inherit the collection interface

public class T6 {
	public static void main(String[] args) {
		Map<Integer, String> map = new HashMap<Integer, String>();
		// store key-value pairs
		map.put(1, "dick");
		map.put(2, "rick");
		map.put(3, "nick");

		String str = map.get(2);// Get data
		System.out.println(str);

		//traverse
		Set<Integer> keys = map.keySet();//Get all keys
		for (Integer key : keys) {
			String str2 = map.get(key);
			System.out.println(key + ":" + str2);
		}
	}
}