如何重写compareTo Double方法？

Question

I tried to override compareTo method however I see compiler uses Java.lang.Double.compareTo method instead of my compareTo .
What is wrong here and what should I fix and change so my own compareTo method will be used?

package GenerecEx;
import java.util.ArrayList;
import java.util.Collections;

public class ArraySort implements Comparable{

double val;
static ArrayList<Double> a=new ArrayList<Double>();

public static void main(String[] args) {
    a.add(2.4);
    a.add(8.4);
    a.add(9.4);
    a.add(4.4);
    a.add(6.4);

    sort(a);
    printList(a);

}

public static void printList(ArrayList a1)
{
    System.out.println(a1.toString());
}

static public void sort(ArrayList <Double> a1)
{
    for (int i=0;i<a1.size();i++){
        for(int j=0;j<a1.size()-i-1;j++){
            if (a1.get(j).compareTo(a1.get(j+1))>0){
                double temp = a1.get(j);
                a1.set(j,a1.get(j+1) );
                a1.set(j+1, temp);
            }
        }
    }

}
@Override
public int compareTo(Object element)
{
    if (this.val < (Double) element)
        return -1;
    else return 1;
}
}

Answer 1

Implementing the Comparable interface allows you to override the compareTo method on the implementing class . Having implemented Comparable on the ArraySort class, your compareTo method should actually be comparing objects of type ArraySort , not generic Object s cast as Double .