Exception Handling - Absolute Java - page 566

9.3 More Programming Techniques for

Exception Handling

Only use this in exceptional circumstances.

WARREN PEACE, The Lieutenant's Tool

In this section, we present a number of the finer points about programming with
exception handling in Java.

PITFALL: Nested try-catch Blocks

You can place a try block and its following catch blocks inside a larger try block
or inside a larger catch block. On rare occasions this may be useful, but it is almost
always better to place the inner try catch blocks inside a method definition and
place an invocation of the method in the outer try or catch block (or maybe just
eliminate one or more try blocks completely).
If you place a try block and its following catch blocks inside a larger catch block,
you will need to use different names for the catch block parameters in the inner and
outer blocks. This has to do with how Java handles nested blocks of any kind. Remem-
ber, try blocks and catch blocks are blocks.
If you place a try block and its following catch blocks inside a larger try block,
and an exception is thrown in the inner try block but is not caught in the inner catch
blocks, then the exception is thrown to the outer try block for processing and might
be caught in one of its catch blocks.

■

The finally Block

The finally block contains code to be executed whether or not an exception is
thrown in a try block. The finally block, if used, is placed after a try block and its
following catch blocks. The general syntax is as follows:

★

try
{
...
}
catch (ExceptionClass1 e)
{
...
}
.
.
.