JuniorTheoryCommon

What happens when this program is compiled and run?

JAVA

public class Main {
    public static void main(String[] args) {
        Integer x = null;
        System.out.println(x);
        int y = x;
        System.out.println(y);
    }
}

Prints null, then a NullPointerException is thrown

Expecting 0 after null: unboxing is a hidden x.intValue() call, so a null wrapper throws NullPointerException instead of turning into zero.
Expecting the error at println(x): printing a null reference is fine and prints null; only the unboxing line fails.

What is the default value of a static Integer field?
How do you get an int safely from an Integer that may be null?

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

public class Main {
    public static void main(String[] args) {
        Integer x = null;
        System.out.println(x);
        int y = x;
        System.out.println(y);
    }
}

Prints null, then a NullPointerException is thrown

Expecting 0 after null: unboxing is a hidden x.intValue() call, so a null wrapper throws NullPointerException instead of turning into zero.
Expecting the error at println(x): printing a null reference is fine and prints null; only the unboxing line fails.

What is the default value of a static Integer field?
How do you get an int safely from an Integer that may be null?

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