public class ChromosomeRanking implements Comparable<ChromosomeRanking>{

    private double ranking;

    private Chromosome chrom;

    @Override

    public int compareTo(ChromosomeRanking cr2) {

        if(this.ranking == cr2.ranking){

            return 0;

        }

        if(this.ranking < cr2.ranking){

            return -1;

        }

        if(this.ranking > cr2.ranking){

            return 1;

        }

        return 0;

    }

  /**

   *Other methods here

   */

}

//Using above class here:

ArrayList<ChromosomeRanking> chromRankList = new ArrayList<ChromosomeRanking>();

//Lines here add members into the ArrayList

//Then calling this sort method:

Collections.sort(chromRankList);

//This code is called in numerous times while the application runs. It is running without any issue sometimes. But most of the times it is returning this exception message:

java.lang.IllegalArgumentException: Comparison method violates its general contract!

    at java.util.ComparableTimSort.mergeLo(Unknown Source)

    at java.util.ComparableTimSort.mergeAt(Unknown Source)

    at java.util.ComparableTimSort.mergeCollapse(Unknown Source)

    at java.util.ComparableTimSort.sort(Unknown Source)

    at java.util.ComparableTimSort.sort(Unknown Source)

    at java.util.Arrays.sort(Unknown Source)

    at java.util.Collections.sort(Unknown Source)

I am very much in need to resolve this issue asap. Any type of help is appreciated. Thanks.