import java.util.ArrayList;

import java.util.Collections;

import java.util.Comparator;

​

class SortEvenFirst implements Comparator {

  public int compare(Object obj1, Object obj2) {

    // Make sure the objects are integers

    Integer a = (Integer)obj1;

    Integer b = (Integer)obj2;

    // Check each number to see if it is even

    // A number is even if the remainder when dividing by 2 is 0

    boolean aIsEven = (a % 2) == 0;

    boolean bIsEven = (b % 2) == 0;

    if (aIsEven == bIsEven) {

      // If both numbers are even or both are odd then use normal sorting rules

      if (a < b) return -1;

      if (a > b) return 1;

      return 0;

    } else {

      // If a is even then it goes first, otherwise b goes first

      if (aIsEven) {

        return -1;

      } else {

        return 1;

      }

    }

  }

}

​

public class Main {

  public static void main(String[] args) {

    ArrayList<Integer> myNumbers = new ArrayList<Integer>();

    myNumbers.add(33);

    myNumbers.add(15);

    myNumbers.add(20);

    myNumbers.add(34);

    myNumbers.add(8);

    myNumbers.add(12);

​

      Comparator myComparator = new SortEvenFirst();

    Collections.sort(myNumbers, myComparator);