JuniorTheoryCommon

What happens when this program is compiled and run?

JAVA

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

public class Main {
    public static void main(String[] args) {
        List<int> xs = new ArrayList<>();
        xs.add(5);
        System.out.println(xs);
    }
}

It does not compile

Expecting [5]: generics accept only reference types, so List<int> does not compile; a list of numbers is List<Integer>, and autoboxing turns 5 into an Integer.
Expecting an error only when the program runs: type arguments are checked by javac, so the program is rejected before it starts.

How do you declare a list of whole numbers instead?
What does autoboxing do when you call xs.add(5) on a List<Integer>?

Back to questions Open topic in roadmap →Answer it yourself — Quiz

Back to questions

JuniorTheoryCommon

What happens when this program is compiled and run?

JAVA

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

public class Main {
    public static void main(String[] args) {
        List<int> xs = new ArrayList<>();
        xs.add(5);
        System.out.println(xs);
    }
}

It does not compile

Expecting [5]: generics accept only reference types, so List<int> does not compile; a list of numbers is List<Integer>, and autoboxing turns 5 into an Integer.
Expecting an error only when the program runs: type arguments are checked by javac, so the program is rejected before it starts.

How do you declare a list of whole numbers instead?
What does autoboxing do when you call xs.add(5) on a List<Integer>?

Back to questions Open topic in roadmap →Answer it yourself — Quiz