在 JDK 7 之前，资源需要手动关闭。
Charset charset = Charset.forName("US-ASCII");
String s = ...;
BufferedWriter writer = null;
try {
writer = Files.newBufferedWriter(file, charset);
writer.write(s, 0, s.length());
} catch (IOException x) {
System.err.format("IOException: %s%n", x);
} finally {
if (writer != null) writer.close();
}
JDK7中，大大化简了这步操作，可以使用如下代码
public class Demo {
public static void main(String[] args) {
try(Resource res = new Resource()) {
res.doSome();
} catch(Exception ex) {
ex.printStackTrace();
}
}
}
class Resource implements AutoCloseable {
void doSome() {
System.out.println("do something");
}
@Override
public void close() throws Exception {
System.out.println("resource is closed");
}
}
JDK9中，又有新的提升
// New and improved try-with-resources statement in JDK 9
try (resource1;
resource2) {
// Use of resource1 and resource 2.
}
不过使用面较小，就不细致讨论了。
