Throw exception inside catch clause

Question

I have two snippet of code :

class PreciseRethrow {
public static void main(String[] str) {
    try {
        foo();
    } catch (NumberFormatException ife)          


        

Answer 1

The difference is that the compiler can see that the only checked exception that can be rethrown in the first example is a NumberFormatException. (You are not creating any new exceptions.) Therefore it is happy with the throws NumberFormatException { declaration in the header.

In the second example however, you are explicitly throwing a checked exception that is not declared in the header, so predictably you get a compiler error.