Does Java have a using statement?

Question

Java 7 introduced Automatic Resource Block Management which brings this feature to the Java platform. Prior versions of Java didn't have anything resembling using.

As an example, you can use any variable implementing java.lang.AutoCloseable in the following way:

try(ClassImplementingAutoCloseable obj = new ClassImplementingAutoCloseable())
{
    ...
}

Java's java.io.Closeable interface, implemented by streams, automagically extends AutoCloseable, so you can already use streams in a try block the same way you would use them in a C# using block. This is equivalent to C#'s using.

As of version 5.0, Hibernate Sessions implement AutoCloseable and can be auto-closed in ARM blocks. In previous versions of Hibernate Session did not implement AutoCloseable. So you'll need to be on Hibernate >= 5.0 in order to use this feature.

Before Java 7, there was no such feature in Java (for Java 7 and up see Asaph's answer regarding ARM).

You needed to do it manually and it was a pain:

AwesomeClass hooray = null;
try {
  hooray = new AwesomeClass();
  // Great code
} finally {
  if (hooray!=null) {
    hooray.close();
  }
}

And that's just the code when neither // Great code nor hooray.close() can throw any exceptions.

If you really only want to limit the scope of a variable, then a simple code block does the job:

{
  AwesomeClass hooray = new AwesomeClass();
  // Great code
}

But that's probably not what you meant.

Since Java 7 it does: http://blogs.oracle.com/darcy/entry/project_coin_updated_arm_spec

The syntax for the code in the question would be:

try (Session session = new Session())
{
  // do stuff
}

Note that Session needs to implement AutoClosable or one of its (many) sub-interfaces.

Technically:

DisposableObject d = null;
try {
    d = new DisposableObject(); 
}
finally {
    if (d != null) {
        d.Dispose();
    }
}

The closest java equivalent is

AwesomeClass hooray = new AwesomeClass();
try{
    // Great code
} finally {
    hooray.dispose(); // or .close(), etc.
}