如何对BigDecimal对象列表进行排序

Question

Given the following input:

-100
50
0
56.6
90

I have added each value as a BigDecimal to a list.

I want to be able to sort the list from highest to lowest value.

I have attempted to do this in the following way:

public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        List<BigDecimal> list = new ArrayList<BigDecimal>();

        while(sc.hasNext()){
            list.add(new BigDecimal(sc.next()));
        }

        Collections.reverse(list);

        for(BigDecimal d : list){

            System.out.println(d);
        }
    }

Which outputs:

90
56.6
0
50
-100

In this instance 50 should be a higher value than 0.

How can I correctly sort a BigDecimal list from highest to lowest taking into account decimal and non decimal values?

Answer 1

In your code you are only calling reverse which reverses the order of the list. You need to sort the list as well, in reversed order .

This will do the trick:

Collections.sort(list, Collections.reverseOrder());

Answer 2

You can use org.apache.commons.collections.list.TreeList . No need to sort. It will keep inserted objects in sorted order. Then you can just reverse it if you want.

Answer 3

You can try this one, it worked for me:

package HackerRank;

import java.util.*;
import java.math.*;

class Sorting
{
    public static void main(String []args)
    {
        Scanner sc = new Scanner(System.in);
        TreeSet<BigDecimal> list = new TreeSet<BigDecimal>();
        int testCase = sc.nextInt();

        while(testCase-- > 0)
            list.add(new BigDecimal(sc.next()));

        System.out.println(list); //ascending order
        System.out.println(list.descendingSet()); //descending order
    }
}