■

import java.util.*;
class ListTest {

  static class Test {
    int a_;
    String b_;
    Test(){
      a_ = 0;
      b_ = "";
    }
  }

  static private int getKeyListIndex(Test a) {
    int index = 0;
    for (String it : keyList) {
      if (a.b_.compareTo(it) == 0) {
        return index;  
      }
      index++;
    }
    return index;
  }

  static private List<String> keyList = new ArrayList<>();

  static public class TestComparator implements Comparator<Test> {
    // @override
    public int compare(Test a, Test b) {
      return getKeyListIndex(a) - getKeyListIndex(b);
    }
  }

  private static List<Test> test_list = new ArrayList<>();

  public static void main(String[] argv) {
    keyList.add("second");
    keyList.add("first");
    keyList.add("third");

    Test a = new Test();
    a.a_ = 2;
    a.b_ = "first";
    Test az = new Test();
    az.a_ = 100;
    az.b_ = "firstest";
     Test b = new Test();
    b.a_ = 1;
    b.b_ = "second";
    Test c = new Test();
    c.a_ = 5;
    c.b_ = "third";
    test_list.add(a);
    test_list.add(az);
    test_list.add(b);
    test_list.add(c);

    System.out.println("before");
    for (Test it : test_list) {
      System.out.println(it.a_ + ":" + it.b_);
    }

    Collections.sort(test_list, new TestComparator());

    System.out.println("");
    System.out.println("after");
    for (Test it : test_list) {
      System.out.println(it.a_ + ":" + it.b_);
    }
  }
}