CODEWITHSUNDEEP
lambdajava-8functional-interface
overexchange
overexchange

Reputation: 1

Is lambda expression actually implementing java interface under the hood?

Below is the java program that uses lambda expression as parameter for sort() method.

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

public class Dummy {

    public static void main(String[] args) {
        List<String> a1 = new ArrayList<String>();
        a1.add("Zara");
        a1.add("Mahnaz");
        a1.add("Ayan");
        Collections.sort(a1,
                            (p1, p2) -> p1.compareTo(p2)

                        );

        System.out.println(a1.toString());
    } //end main

}

Using Eclipse, When I say F3 on sort() method, control is again actually going to same sort() method signature(definiton) used in java 7 version.

@SuppressWarnings({"unchecked", "rawtypes"})
    public static <T> void sort(List<T> list, Comparator<? super T> c) {
        //whatever
    }

In my code, Does the syntax of second parameter in sort() method is actually equivalent to implementing interface Comparator<T>, under the hood? something like 

class ComparePersonsbyName implements Comparator<String>{
    public int compareTo(String p1, String p2){
        return p1.compareTo(p2);        
    }
}
Collections.sort(a1, new ComparePersonsbyName());

Upvotes: 1

Views: 423

Answers (1)

Yosef Weiner
Yosef Weiner

Reputation: 5751

Yes, Comparator is a functional interface

Upvotes: 4

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