Java NPE in ternary operator with autoboxing?

Question

I ran across a very weird NPE this morning, and reduced it to a simple example. Is this a JVM bug or correct behavior?

public class Test1 {
    class Item {
         


        

Answer 1

The return type below is Integer -

public Integer f() {
    Item item = new Item();
    // this works:
    //return item == null ? new Integer(1) : item.getId();

    // NPE??
    return item == null ? 1 : item.getId();
}

And the result of the following -

item == null ? 1 : item.getId()

is null in your case.

So, JVM is throwing NPE because it is trying to autobox null.

Try -

new Integer(null); // and
Integer.valueOf(null);

both will throw NPE.