Java reference

AutoCloseable

The interface of a resource that can be closed by try-with-resources.

Available since: Java 7

Syntax

public interface AutoCloseable {
    void close() throws Exception;
}

Examples

Resources are closed in reverse order:

record Resource(String name) implements AutoCloseable {
    Resource {
        IO.println("open " + name);
    }
    public void close() {
        IO.println("close " + name);
    }
}
 
void main() {
    try (var a = new Resource("A"); var b = new Resource("B")) {
        IO.println("working");
    }
}

Output:

open A
open B
working
close B
close A

Notes

Implement it in your classes that hold a file, a connection or a lock. The interface declares close() with throws Exception, but your implementation may throw a narrower exception or none — then no catch is needed. Its subinterface Closeable from java.io uses throws IOException.

Related recipes

How to close resources automatically

In the tutorial

try-with-resources — Closing resources automatically in Java — try-with-resources, the AutoCloseable interface, several resources, closing order and suppressed exceptions.

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