CODEWITHSUNDEEP
javajava-8
reza ramezani matin
reza ramezani matin

Reputation: 1474

How to get an Object due to maximum result of a method in java 8

I want to rewrite the below for-loop-statement by lambda expression of java8.

public class Test {

    List<ObjectTest> lst;

    public int operation(int a, int b) {
        return a * b;
    }

     int max = 0;
     ObjectTest suitableObj = null;
     for(ObjectTest obj:lst) {
        int result = operation(obj.getA(), obj.getB());
        if(result > max) {
            suitableObj = obj;
            max = result;
        }
     }
}

How is it possible by lambda expression?

Upvotes: 2

Views: 94

Answers (2)

senjin.hajrulahovic
senjin.hajrulahovic

Reputation: 3191

@Eran's answer is the most concise, but you should consider writing an overloaded method:

public int operation(ObjectTest o) {
    return o.getA() * o.getB();
}

Then you could simply write:

import static java.util.Comparator.comparing;
import static java.util.stream.Collectors.maxBy;

list.stream().max(comparing(Test::operation)).orElse(null);

to obtain the object for which operation yields the maximum result, and

list.stream().maToInt(comparing(Test::operation)).max().orElse(0);

to obtain the the maximum result.

Upvotes: 0

Eran
Eran

Reputation: 393856

You can Stream your ObjectTest elements, map them to an IntStream and call the max() method to compute the maximum value:

int max = lst.stream()
             .mapToInt(obj->operation(obj.getA(), obj.getB()))
             .max()
             .orElse(0); // default value in case the input List is empty

EDIT: If you want, after your edit, to find the ObjectTest instance having the max value of operation(obj.getA(), obj.getB()), you can use Stream's max(Comparator<? super T> comparator):

ObjectTest max = lst.stream()
                    .max(Comparator.comparingInt(obj->operation(obj.getA(), obj.getB())))
                    .orElse(null);

Upvotes: 7

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