Custom sorting of list of objects using Java Stream

Java

Sometimes you need to sort list of objects such that few elements are sorted in ascending order and few elements are sorted in descending order.

Let’s say you have below Java POJO class:

package com.custom.sorting.model;

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

@NoArgsConstructor
@AllArgsConstructor
@Builder
@Data
public class Seller {
    String sellerName;
    Double distanceFromMyLocation;
    String sellerState;
    Double sellerRating;
}

Now, say you have list of Seller objects and want to sort as mentioned below such that:

1. list will be sorted in ascending order of distanceFromMyLocation
2. list will be sorted in descending order of sellerRating
3. list will be sorted in ascending order of sellerName
4. list will be sorted in ascending order of sellerState

To do as above we can use Comparator class of Java.

We can write separate comparators for each attributes to be used in sorting.

Java code:

package com.custom.sorting.service;

import com.custom.sorting.model.Seller;

import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.stream.Collectors;

public class CustomSorting {

    public static void main(String[] args) {
        List<Seller> sellerList = getSampleListOfSellers();

        //seller name comparator
        Comparator<Seller> sellerNameComparator = Comparator.comparing(Seller::getSellerName);

        //seller location distance comparator
        Comparator<Seller> sellerLocationDistanceComparator = Comparator.comparing(Seller::getDistanceFromMyLocation);

        //seller state comparator
        Comparator<Seller> sellerStateComparator = Comparator.comparing(Seller::getSellerState);

        //seller rating comparator
        Comparator<Seller> sellerRatingComparator = Comparator.comparing(Seller::getSellerRating);

        Comparator<Seller> finalComparator = sellerLocationDistanceComparator
                .thenComparing(sellerRatingComparator.reversed())
                .thenComparing(sellerNameComparator)
                .thenComparing(sellerStateComparator);

        List<Seller> sortedSellerList = sellerList.stream()
                .sorted(finalComparator)
                .collect(Collectors.toList());

        sortedSellerList.forEach(seller -> System.out.println(seller.toString()));
    }

    public static List<Seller> getSampleListOfSellers() {
        return Arrays.asList(
                getSeller("Alice", 60.0, "Goa", 3.8),
                getSeller("Bob", 12.0, "Delhi", 4.2),
                getSeller("Alex", 12.0, "Kerala", 4.5),
                getSeller("Roy", 56.7, "Maharashtra", 4.4),
                getSeller("Mark", 125.0, "Gujarat", 4.0),
                getSeller("Eric", 125.0, "Gujarat", 4.0)
        );
    }

    public static Seller getSeller(String sellerName,
                                   Double distanceFromMyLocation,
                                   String sellerState,
                                   Double sellerRating) {
        return Seller.builder().sellerName(sellerName)
                .distanceFromMyLocation(distanceFromMyLocation)
                .sellerState(sellerState)
                .sellerRating(sellerRating)
                .build();
    }

}

Output:

Seller(sellerName=Alex, distanceFromMyLocation=12.0, sellerState=Kerala, sellerRating=4.5)
Seller(sellerName=Bob, distanceFromMyLocation=12.0, sellerState=Delhi, sellerRating=4.2)
Seller(sellerName=Roy, distanceFromMyLocation=56.7, sellerState=Maharashtra, sellerRating=4.4)
Seller(sellerName=Alice, distanceFromMyLocation=60.0, sellerState=Goa, sellerRating=3.8)
Seller(sellerName=Eric, distanceFromMyLocation=125.0, sellerState=Gujarat, sellerRating=4.0)
Seller(sellerName=Mark, distanceFromMyLocation=125.0, sellerState=Gujarat, sellerRating=4.0)

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