While messing around with the custom formatting options in Eclipse, in one of the sample pieces of code, I saw code as follows:
/**
* 'try-with-resources'
*/
class Example {
void foo() {
try (FileReader reader1 = new FileReader("file1"); FileReader reader2 = new FileReader("file2")) {
}
}
}
I've never seen try used like this and I've been coding in Java for 9 years! Does any one know why you would do this? What is a possible use-case / benefit of doing this?
An other pieces of code I saw, I thought was a very useful shorthand so I'm sharing it here as well, it's pretty obvious what it does:
/**
* 'multi-catch'
*/
class Example {
void foo() {
try {
} catch (IllegalArgumentException | NullPointerException | ClassCastException e) {
e.printStackTrace();
}
}
}
Source: Tips4all, CCNA FINAL EXAM
It was added in Java 7. It's called the try-with-resources statement.
ReplyDelete/edit
Might as well throw this in here too. You can use the try-with-resources statement to manage Locks if you use a wrapper class like this:
public class CloseableLock implements Closeable {
private final Lock lock;
private CloseableLock(Lock l) {
lock = l;
}
public void close() {
lock.unlock();
}
public static CloseableLock lock(Lock l) {
l.lock();
return new CloseableLock(l);
}
}
try(CloseableLock l = CloseableLock.lock(lock)) { // acquire the lock
// do something
} // release the lock
However, since you have to declare a variable for every resource, the advantage of this is debatable.
This is Java 7's new try-with-resources statement: http://download.oracle.com/javase/7/docs/technotes/guides/language/try-with-resources.html
ReplyDeleteThose are changes introduced in JDK7.
ReplyDeleteFirst statement is a try-with-resources. I don't know exactly why they exist but exceptions are often caused by inputstreams etc, I guess it just improves readability. Edit: thanks to the other answerers, I read the javadoc and I now know that it will close all i/o streams that implement AutoCloseable, omitting the need for a finally block in a lot of situations
Second is a multi-catch, which is really handy when you have different exceptions that you handle in exactly the same way.
It's called try-with-resource. It's a way so as to not have to clean after yourself as the language will do it for you.
ReplyDeleteThat is called with a try with resources. in a try with resources, any kind of closable stream declared in the resources section will be closed after the try statement is done. So it pretty much is a
ReplyDeletetry{
InputStream is;
//Stuff
}finally{
is.close()
}