Question

As I know if method throws an exception Java compiler forces the caller of that method to catch that exception.

I see that parseInt throws NumberFormatException :

public static int parseInt(String s) throws NumberFormatException {
    return parseInt(s,10);

So why I can call it wthout catching the exception :

String str = "5";
int n = Integer.parseInt(str);

Answer 1

Because NumberFormatException extends RuntimeException – Runtime Exceptions are considered to be ‘unchecked’, See the Javadoc of RuntimeException:

RuntimeException is the superclass of
those exceptions that can be thrown
during the normal operation of the
Java Virtual Machine.

A method is not required to declare in
its throws clause any subclasses of
RuntimeException that might be thrown
during the execution of the method but
not caught.

Here is an article from the Java tutorial explaining how this feature is meant and why it exists