Does Java have a using statement?

Question

Does Java have a using statement that can be used when opening a session in hibernate?

In C# it is something like:

using (var session = new Session()         


        

Answer 1

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.

Answer 2

Technically:

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

Answer 3

As of now, no.

However there is a proposal of ARM for Java 7.

Answer 4

To answer the question regarding limiting scope of a variable, instead of talking about automatically closing/disposing variables.

In Java you can define closed, anonymous scopes using curly brackets. It's extremely simple.

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

The variable hooray is only available in this scope, and not outside it.

This can be useful if you have repeating variables which are only temporary.

For example, each with index. Just like the item variable is closed over the for loop (i.e., is only available inside it), the index variable is closed over the anonymous scope.

// first loop
{
    Integer index = -1;
    for (Object item : things) {index += 1;
        // ... item, index
    }
}

// second loop
{
    Integer index = -1;
    for (Object item : stuff) {index += 1;
        // ... item, index
    }
}

I also use this sometimes if you don't have a for loop to provide variable scope, but you want to use generic variable names.

{
    User user = new User();
    user.setId(0);
    user.setName("Andy Green");
    user.setEmail("andygreen@gmail.com");
    users.add(user);
}

{
    User user = new User();
    user.setId(1);
    user.setName("Rachel Blue");
    user.setEmail("rachelblue@gmail.com");
    users.add(user);
}

Answer 5

Please see this List of Java Keywords.

1. The using keyword is unfortunately not part of the list.
2. And there is also no equivalence of the C# using keyword through any other keyword as for now in Java.

To imitate such "using" behaviour, you will have to use a try...catch...finally block, where you would dispose of the resources within finally.

Answer 6

In java 8 you can use try. Please refer to following page. http://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html