CODEWITHSUNDEEP
javasortingarraylistlambdajava-8
sudo-potato
sudo-potato

Reputation: 171

Dereferenced Int Value With Lambdas

I'm trying to sort and print an ArrayList that is sorted by ID.

clientArr.sort( (p1, p2) -> p1.getAccount().getID().compareTo(p2.getAccount().getID()) );
for(Client client : clientArr)
    System.out.println(client);

I believe my issue is because p1 and p2 are expecting objects to be returned, but they are getting int values. How would I go about fixing this?

The ArrayList stores Client objects. Client class contains String values (not important in this example) and it creates an instance of an Account object. Within the Account class is stored the int ID value. That's the value I need

Upvotes: 2

Views: 178

Answers (2)

Elliott Frisch
Elliott Frisch

Reputation: 201527

Use Integer.compare(int, int) like,

clientArr.sort((p1, p2) -> Integer.compare(p1.getAccount().getID(), 
                                           p2.getAccount().getID()));

Also, your for-each loop could be rewritten like

clientArr.forEach(System.out::println);

Upvotes: 6

Hitesh Garg
Hitesh Garg

Reputation: 1211

You can do all this stuff in just one go and in a functional way that Java8 suggests -

Use sorted of Stream API and provide a comparator as the method reference.

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

public class ComparingTest {

    public static void main(String[] args) {
        List<Test> mTestList = new ArrayList<>();
        mTestList.add(new Test(10));
        mTestList.add(new Test(1));
        mTestList.add(new Test(5));
        mTestList.add(new Test(4));
        mTestList.add(new Test(2));
        mTestList.add(new Test(8));
        mTestList.add(new Test(7));

        mTestList.stream().sorted(Comparator.comparingInt(Test::getId)).forEach(System.out::println);
    }
}

class Test {
    public int id;

    Test(int id) {
        this.id = id;
    }

    public int getId() {
        return id;
    }

    @Override
    public String toString() {
        return String.valueOf(getId());
    }
}

Upvotes: 1

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