MapTest.java

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

class User {
	private String name;
	private String email;

	public User(String name, String email) {
		this.name = name;
		this.email = email;
	}

	public String getName() {
		return name;
	}

	public String getEmail() {
		return email;
	}
}

public class MapTest {
	public static void main(String [] args) {
		Map<String, User> map = new HashMap<>();
		User user1 = new User("name1", "[email protected]");
		User user2 = new User("name2", "[email protected]");
		User user3 = new User("name3", "[email protected]");
		User user4 = new User("name4", "[email protected]");

		map.put(user1.getName(), user1);
		map.put(user2.getName(), user2);
		map.put(user3.getName(), user3);
		map.put(user4.getName(), user4);

		for (Map.Entry<String, User> entry : map.entrySet()) {
			String key = entry.getKey();
			User tmpUser = entry.getValue();
			System.out.println(key + " : " + tmpUser.getName() + " : " + tmpUser.getEmail());
		}
		try {
			FileWriter fw = new FileWriter("D:\\user.txt");
			for (String key : map.keySet()) {
				User tmpUser = map.get(key);
				String line = tmpUser.getName() + " " + tmpUser.getEmail();
				System.out.println(line);
				fw.write(line + "\r\n");
			}
			fw.close();	
		} catch(Exception e) {

		}
	}
}