try-with-resources in Java

Try-with-resources allows us to declare resources to be used in a try block with the assurance that the resources will be closed when after the execution of that block. Up until Java 8, the try-with-resources statement could only close resources declared inside the statement itself. As of Java 9, this statement can also close predefine resource, provided those resources are reference with parentheses immediately after the try keyword.
Let's compare the following code samples – first is a typical try-catch-finally block, then the new approach, using an equivalent try-with-resources block:
```
Scanner scanner = null;
try {
    scanner = new Scanner(new File("test.txt"));
    while (scanner.hasNext()) {
        System.out.println(scanner.nextLine());
    }
} catch (FileNotFoundException e) {
    e.printStackTrace();
} finally {
    if (scanner != null) {
        scanner.close();
    }
}
//////////////////////////
try (Scanner scanner = new Scanner(new File("test.txt"))) {
    while (scanner.hasNext()) {
        System.out.println(scanner.nextLine());
    }
} catch (FileNotFoundException fnfe) {
    fnfe.printStackTrace();
}
```
Multiple resources can be declared just fine in a try-with-resources block by separating them with a semicolon.
To construct a custom resource that will be correctly handled by a try-with-resources block, the class should implement the Closeable or AutoCloseable interfaces, and override the close method.
Resources are closed in the reverse order from which they were created. That is, resources that were defined/acquired first will be closed last.
Resources are closed after the try clause ends and before any catch/finally clauses.
A try-with-resources block can still have the catch and finally blocks – which will work in the same way as with a traditional try block.
If an exception is thrown from the try block and one or more exceptions are thrown from the try-with-resources statement, then those exceptions thrown from the try-with-resources statement are suppressed
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