Initialization And Default Values

I have a question related to q44 of Examlab.

public static void main(String... args) {
String i;
// String i = null; that would compile
if (i == null) {// this line does not compile as i was not initialized
System.out.print("A");
} else {
System.out.print("B");
i = "A";
main("A", "B");
}
}

Why does the above code not compile although the statement String i should lead to an initialisation of i to the value of null which is the default value for Strings.