Question

eWhile catching exceptions is this necessary to check if the error message is not null to avoid null pointer exception? Another words, is the if (e!=null) part needed? or e is always not null?

 try {
     ...

  } catch(Exception e) {
     if (e != null) {
        System.err.println("Error: " + e.getMessage());
     }

  }

Answer 1

Anything that gets thrown must be a subclass of Throwable, and your catch will only catch things that are a subclass of Exception. Therefore you can neither throw nor catch null, therefore checking for nullality is not necessary. If you use throw null or throw a variable that contains null then it will throw a NullPointerException.