异常谜题之关闭流

这里忽然想到，其实这个知识点当时看马士兵的视频教程的时候看到过，但是没有仔细的研究：

static void copy(String src, String dest) throws IOException {
        InputStream in = null;
        OutputStream out = null;
        try {
            in = new FileInputStream(src);
            out = new FileOutputStream(dest);
            byte[] buf = new byte[1024];
            int n;
            while ((n = in.read(buf)) > 0)
                out.write(buf, 0, n);
        } finally {
            if (in != null) in.close();
            if (out != null) out.close();
        } 
}

上面这个方法会不会出现意外？会！！问题就在close方法上面，如果in.close方法出现异常，下面的根本就没法执行了。所以改正如下：

} finally {
     if (in != null) {
          try {
              in.close();
          } catch (IOException ex) {
              // There is nothing we can do if close fails
          }
     if (out != null)
          try {
              out.close();
          } catch (IOException ex) {
              // There is nothing we can do if close fails
          }
    } 
}

或者重构一下：

} finally {
     closeIgnoringException(in);
     closeIgnoringEcception(out);
}
private static void closeIgnoringException(Closeable c) {
     if (c != null) {
           try {
             c.close();
           } catch (IOException ex) {
             // There is nothing we can do if close  fails
           }
     }
}