Try-with-resources on an existing variable

新版本的变更 / Java 9

import java.util.Scanner;

// *** before: ***
Scanner s1 = new Scanner("one two");
try (Scanner copy = s1) {        // an extra variable only to close the resource
    System.out.println(copy.next());
}

// *** in version 9: ***
Scanner s2 = new Scanner("one two");
try (s2) {                       // an effectively final variable is enough
    System.out.println(s2.next());
}