AutoClosable in Java

AutoCloseable makes it possible to use the try-with-resources idiom:
```
import java.lang.Exception;
import java.io.IOException;

public class Main implements AutoCloseable {
    void open() {
        System.out.println("Open");
    }
    String read() throws IOException {
        throw new IOException();
    }
    public void close() throws Exception {
        System.out.println("Close");
    }
    public static void main(String[] args) {
        try(Main m = new Main()) {
            m.open();
            m.read();
            m.close();
        } catch(Exception e) {
            System.out.println("Exception");
        }
    }
}
```
Now you can say:
```
        try(Main m = new Main()) {
            m.open();
            m.read();
            m.close();
        }
```
and JVM will call close() automatically for you.
Closeable is an older interface. To preserve backward compatibility, language designers decided to create a separate one. This allows not only all Closeable classes (like streams throwing IOException) to be used in try-with-resources, but also allows throwing more general checked exceptions from close().
When in doubt, use AutoCloseable, users of your class will be grateful.
Home