Java Handling Exceptions.

Java Catching and Handling Exceptions

• You use the try, catch, and finally blocks — to write an exception handler.
  try, catch, and finally blocks example:

  ...
    public void writeList() {
      PrintWriter out = null;
      try {
        System.out.println("Entering >try statement");
        out = new PrintWriter(new FileWriter("OutFile.txt"));
        for (int i = 0; i < SIZE; i++) {
          out.println("Value at: " + i + " = " + vector.elementAt(i));
        }
      } catch (ArrayIndexOutOfBoundsException e) {
        System.err.println("Caught " +
                "ArrayIndexOutOfBoundsException: " + e.getMessage());
      } catch (IOException e) {
        System.err.println("Caught IOException: " + e.getMessage());
      } finally {
        if (out != null) {
          System.out.println("Closing PrintWriter");
          out.close();
        } else {
          System.out.println("PrintWriter not open");
        }
      }
    }
  ...

• Specifying the Exceptions Thrown by a Method (in this case an IOException):

  ...
    public void writeList() throws IOException {
      Vector vector = new Vector();
      PrintWriter out = new PrintWriter(new FileWriter("OutFile.txt"));
      for (int i = 0; i < 10; i++) {
        out.println("Value at: " + i + " = " + vector.elementAt(i));
      }
      out.close();
    }
  ...

• When you make the methods throws an exception a calling method should handle the exception.