Question

Looking at a question I got wrong on a midterm test, this has me wondering:

public double[] readInputFile(String fielane) throws IOException
{
  File inputFile = new File(filename);
  Scanner in = new Scanner(inputFile);
  try
  {
    readData(in);
    return data;
  }
  finally
  {
    inputFile.close();
  }
}

Will this pass all exceptions back up the chain, or will it only pass the checked IOException?

Answer 1

The finally block will be executed, and then originally-thrown exception (that is, the first exception that was thrown as a result of readData(in)) will percolate up.

I suppose that the caveat in this question is about the type of exception that will be percolated up. That could either be an IOException, or any sort of unchecked exception (that is, subclasses of java.lang.RuntimeException or java.lang.Error).

EDITED as per @zapl’s comment: if the finally block throws an IOException (as a result of inputFile.close()), that exception will be percolated to the caller, regardless of whether the try block threw an exception or not.