public class User {
   private String name;
   private static Map<String, User> users = new HashMap<>();


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

   public String getName() {
       return name;
   }

   public static User getUser(String name) {
       User user = users.get(name);
       if (user == null) user = new User(name);
       return user;
   }
}

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

public class User {
  private String name;
  private static Map<String, User> users = new HashMap<>();

  private User(String name) {
    this.name = name;
    users.put(name, this);
  }

  public String getName() {
    return name;
  }

  public static User getUser(String name) {
    if (!users.containsKey(name)) users.put(name, new User(name));
    return users.get(name);
  }

}