Java streams to compare between objects and return that object?

Question

I have an ArrayList of a class object like below:

ArrayList<Score> scoreboard = new ArrayList<>();

The Score class has a field points:

class Score {
    private int points; 
    //constructor and methods
}

How would i go about using Java streams to compare the points in each of this Score object and return the object with the highest/lowest value?

I tried something like this but it did not work:

scoreboard
    .stream()
    .max(Comparator.comparing(Score::getPoints)
    .get()
    .forEach(System::println);

define not working.

Ousmane D.
– Ousmane D.

2018-02-04 15:22:00 +00:00
Commented Feb 4, 2018 at 15:22 — Ousmane D.
– Ousmane D., Commented Feb 4, 2018 at 15:22

Andy Turner · Accepted Answer · 2018-02-05 06:20:04Z

5

Look carefully at what you tried:

scoreboard.stream().max(Comparator.comparing(Score::getPoints).get().forEach(System::println);

Here, you're trying to create a Comparator:

Comparator.comparing(Score::getPoints).get().forEach(System::println)

and you've not balanced the parentheses; and you're using a non-existent method, System::println.

Put the parentheses in the right place:

Score maxScore = scoreboard.stream().max(Comparator.comparingInt(Score::getPoints)).get();
                                                                        // Extra  ^

Then print it:

System.out.println(maxScore);

Or, if you're not sure that the stream is non-empty:

Optional<Score> opt = scoreboard.stream().max(...);
opt.ifPresent(System.out::println);

edited Feb 5, 2018 at 6:20

answered Feb 4, 2018 at 15:22

Andy Turner

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