AutoCloseable

AutoCloseable is an interface in java.lang introduced in Java 7 to standardize resource management. It declares a single method close() throws Exception. Implementing classes represent resources that must be released when no longer needed.

AutoCloseable is the superinterface of Closeable; Closeable is a subinterface whose close() method declares IOException. Thus, all Closeable resources are AutoCloseable, but not all AutoCloseable resources are Closeable. The interface enables the try-with-resources statement.

With try-with-resources, resources declared in the try parentheses are automatically closed at the end of the block. They are closed in reverse order of creation. If an exception is thrown within the try block, and a second exception is thrown during close, the latter is added as a suppressed exception to the primary one.

Best practices: resources should be final or effectively final to use in the try-with-resources statement. The close method may throw a checked exception, hence the declaration. In practice, many standard resources implement Closeable.

Example: try (AutoCloseableResource r = new AutoCloseableResource()) { r.doWork(); } // r.close() executes automatically.