javac not considering a function which only throws RuntimeExceptions

A DESCRIPTION OF THE PROBLEM :
I refactored single line below
throw new RuntimeException("Error");
into a function
public void throwException() throws RuntimeException {
throw new RuntimeException("Error");
}

There was a method
public String test(String msg) throws RuntimeException {
If(msg == null)
  throwException();
else
  return msg;
}

The above method is showing compilation error which is not logical.