User

import java.util.Map;
import java.util.Map.Entry;
import java.util.Scanner;
import java.util.TreeMap;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class User {
  public static void main(String[] args) {
    Map<String, String> user = new TreeMap<String, String>();
    user.put("taro", "pass1");
    user.put("hanako", "pass2");
    StringBuilder sb1 = new StringBuilder();
    sb1.append("username taro password pass1\n");
    sb1.append("username jiro password pass3\n");
    Scanner in = new Scanner(sb1.toString());
    Pattern re = Pattern.compile("username (\\w+) password (\\w+)");
    while (in.hasNextLine()) {
      Matcher m = re.matcher(in.nextLine());
      if (m.find()) {
        boolean found = false;
        for (Entry<String, String> e : user.entrySet()) {
          if (e.getKey().equals(m.group(1))) {
            System.out.println(m.group(1) + "はすでに登録されています");
            found = true;
            break;
          }
        }
        if (!found) {
          user.put(m.group(1), m.group(2));
          System.out.println("新しく" + m.group(1) + "を登録しました");
        }
      }
    }
    in.close();
    StringBuilder sb2 = new StringBuilder();
    for (Entry<String, String> e : user.entrySet()) {
      sb2.append("User: " + e.getKey() + "\n");
    }
    System.out.println(sb2);
  }
}