Re: different try-finally approach

From:

Bill McCleary <mccleary.b@folderol.cs.uhtx.edu>

Newsgroups:

comp.lang.java.programmer

Date:

Mon, 03 Aug 2009 04:35:04 -0400

Message-ID:

<h567u2$b46$1@news.eternal-september.org>

Pitch wrote:

In java it is common to check if the resource is null in finally
statement, before closing it:

public void doSomething() throws MyResourceException
{
  MyResource res = null;
  try
  {
    res = new MyResource();
    // do something
  }
  finally
  {
    if (res != null) res.close()
  }
}

But in some other languages this is the preferred way:

public void doSomething() throws MyResourceException
{
  MyResource res = new MyResource();
  try
  {
    // do something
  }
  finally
  {
    res.close()
  }
}

The first example ensures nothing more than the second one, right? If
the constructor throws an exception the "res" is null, so it can't be
closed anyways.

So, my question is - why the extra coding in java? Am I missing
something?

If there's more than one resource, the latter form to be exception safe
has to be nested several times, each one in the previous one's try
block. The former form, on the other hand, avoids all this nesting and
deep indentation becoming:

public void doSomething() throws MyResourceException
{
   MyResource foo = null;
   AnotherResource bar = null;
   Quuxulator baz = null;
   try
   {
     foo = new MyResource();
     bar = ...;
     // do something
     baz = ...;
     // do some more
   }
   finally
   {
     if (foo != null) foo.close()
     if (bar != null) bar.close()
     if (baz != null) baz.close()
   }
}