The AutoCloseable interface is a functional interface introduced in Java 7 that defines a single method called close(). This interface is used to ensure that resources are closed automatically when they are no longer needed, without the need for manual intervention.

In Java, when working with resources such as files, database connections, network sockets, or other system resources, it's important to make sure that these resources are properly closed after they are no longer needed. Failing to close resources can lead to memory leaks and other issues.

The AutoCloseable interface is designed to simplify this process. Any class that implements the AutoCloseable interface can be used with a try-with-resources statement, which automatically calls the close() method when the statement completes, even if an exception is thrown.

Here's an example of how to use the AutoCloseable interface with a try-with-resources statement to ensure that a file is properly closed:

try (FileInputStream fis = new FileInputStream("myfile.txt")) {
    // code to read from the file
} catch (IOException e) {
    // exception handling
}

In this example, the FileInputStream class implements the AutoCloseable interface, so it can be used in a try-with-resources statement. The close() method of the FileInputStream class will be called automatically when the try block completes, whether or not an exception is thrown.

Here's an example implementation of the AutoCloseable interface:

public class MyResource implements AutoCloseable {

    public MyResource() {
        // code to initialize the resource
    }

    public void doSomething() throws Exception {
        // code to use the resource
    }

    @Override
    public void close() throws Exception {
        // code to release the resource
    }
}

In this example, MyResource is a class that implements the AutoCloseable interface. It has a constructor that initializes the resource, a method doSomething() that uses the resource, and a close() method that releases the resource.

To use this class with a try-with-resources statement, you would do something like this:

try (MyResource resource = new MyResource()) {
    resource.doSomething();
} catch (Exception e) {
    // exception handling
}

In this example, the MyResource object is created within the try block and automatically closed at the end of the block, regardless of whether an exception is thrown or not. The doSomething() method can use the resource without worrying about closing it explicitly, because the close() method will be called automatically when the try block completes.