What is Round brackets / parentheses () in try catch in Java

Question

As per as my knowledge we use try catch as follows:

try {    //Some code that may generate exception } catch(Exception ex) { }    //handle exception finally {    //close any open resources etc. } 

But in a code I found following

try(     ByteArrayOutputStream byteArrayStreamResponse  = new ByteArrayOutputStream();                        HSLFSlideShow   pptSlideShow = new HSLFSlideShow(                                       new HSLFSlideShowImpl(  Thread.currentThread().getContextClassLoader()        .getResourceAsStream(Constants.PPT_TEMPLATE_FILE_NAME)                                      ));  ){ } catch (Exception ex) {        //handel exception } finally {       //close any open resource } 

I am not able to understand why this parentheses () just after try.

What is the usage of it? Is it new in Java 1.7? What kind of syntax I can write there?

Please also refer me some API documents.

Answer 1

It is try with Resources syntax which is new in java 1.7. It is used to declare all resources which can be closed. Here is the link to official documentation. https://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html

static String readFirstLineFromFile(String path) throws IOException { try (BufferedReader br =                new BufferedReader(new FileReader(path))) {     return br.readLine(); } } 

In this example, the resource declared in the try-with-resources statement is a BufferedReader. The declaration statement appears within parentheses immediately after the try keyword. The class BufferedReader, in Java SE 7 and later, implements the interface java.lang.AutoCloseable. Because the BufferedReader instance is declared in a try-with-resource statement, it will be closed regardless of whether the try statement completes normally or abruptly (as a result of the method BufferedReader.readLine throwing an IOException).