New/strange Java "try()" syntax?

Question

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();         }     } } 

Answer 1

It was added in Java 7. It's called the try-with-resources statement.

/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.

Answer 2

This is Java 7's new try-with-resources statement: http://download.oracle.com/javase/7/docs/technotes/guides/language/try-with-resources.html