How can I sort a Java list using two different values?

Question

public void sortLeagueTable(List<LeagueTableItem> table) {
    Collections.sort(table, new Comparator<LeagueTableItem>(){
        public int compare(LeagueTableItem o1, LeagueTableItem o2){
            return o2.getPoints() - o1.getPoints();
        }
    });
}

This code sorts two lists based on the value of the object called points. After I sort it based on the value point I want to sort it again based on the value goalScored. So, if the points of two teams are equal, I want to sort it again based on the goalScored value.

How can I do that?

Possible duplicate of Using Comparable for multiple dynamic fields of VO in java — SedJ601
– SedJ601, Commented Dec 4, 2017 at 14:35

Mureinik · Accepted Answer · 2017-12-04 14:44:47Z

9

Java 8's enhancements to the Comparator interface give you a pretty elegant way of achieving this:

table.sort(Comparator.comparingInt(LeagueTableItem::getPoints)
                     .thenComparingInt(LeagueTableItem::goalScored));

edited Dec 4, 2017 at 14:44

answered Dec 4, 2017 at 14:38

Mureinik

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Comments

sma · Accepted Answer · 2017-12-04 14:35:44Z

2

Just add another condition to your comparator:

public int compare(LeagueTableItem o1, LeagueTableItem o2){
     int diff = o2.getPoints() - o1.getPoints();
     if (diff == 0) {
        diff = o2.goalScored() - o1.goalScored();
     }
     return diff;
}

answered Dec 4, 2017 at 14:35

sma

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Comments

Stiliyan Koev · Accepted Answer · 2017-12-07 14:24:31Z

1

public int compare(LeagueTableItem o1, LeagueTableItem o2) {
        if (o2.getPoints() == o1.getPoints()) {

            return o2.goalsScored() - o1.goalsScored();
        } else {
            return o2.getPoints() - o1.getPoints();
        }
    }

First it gets the o1 and o2's points and compare them. If they are equal, the if statement proceed to calculate which o has more goals scored and returns the result, else if the points are NOT equal it returns the result.

edited Dec 7, 2017 at 14:24

answered Dec 4, 2017 at 14:37

Stiliyan Koev

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1 Comment

Toby Speight Over a year ago

Thank you for this code snippet, which might provide some limited, immediate help. A proper explanation would greatly improve its long-term value by showing why this is a good solution to the problem, and would make it more useful to future readers with other, similar questions. Please edit your answer to add some explanation, including the assumptions you've made.

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