How does try-with-resources prevent resource leaks in Java?

Explains deterministic cleanup through AutoCloseable, reverse close order, suppressed exceptions, and clear ownership.

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A try-with-resources statement owns one or more objects that implement AutoCloseable. Java closes those resources automatically when control leaves the block, whether the body succeeds or throws. Multiple resources are closed in reverse order of declaration. This prevents cleanup from being skipped on an early return or exception. It is different from garbage collection: a resource may hold a file descriptor, socket, or pooled database connection that must be released promptly even though its Java object is still reachable or has not been collected.

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Resource lifetime, close ordering, failure preservation, and the distinction between memory collection and external-resource cleanup.

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Overview
Garbage collection manages memory reachability; try-with-resources manages deterministic release of resources such as files, sockets, and database handles.
A try-with-resources statement owns one or more objects that implement AutoCloseable. Java closes those resources automatically when control leaves the block, whether the body succeeds or throws. Multiple resources are closed in reverse order of declaration. This prevents cleanup from being skipped on an early return or exception. It is different from garbage collection: a resource may hold a file descriptor, socket, or pooled database connection that must be released promptly even though its Java object is still reachable or has not been collected.
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If the body throws and close also throws, the body exception remains the primary failure and the close failure is attached as a suppressed exception. That preserves both pieces of diagnostic information. Ownership should still be explicit: the code that opens the resource normally closes it, while a borrowed framework-managed connection or stream follows the framework's contract. Returning a lazy stream backed by a closed file or result set is a common lifetime bug.

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Relying on garbage collection to close files or connections.
Closing resources in the wrong ownership layer.
Returning lazy data that depends on a resource already closed.
Ignoring suppressed exceptions during diagnosis.

How does try-with-resources prevent resource leaks in Java?

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