private static void customBufferStreamCopy(File source, File target) {
    InputStream fis = null;
    OutputStream fos = null;
    try {
        fis = new FileInputStream(source);
        fos = new FileOutputStream(target);
  
        byte[] buf = new byte[8192];
  
        int i;
        while ((i = fis.read(buf)) != -1) {
            fos.write(buf, 0, i);
        }
    }
    catch (Exception e) {
        e.printStackTrace();
    } finally {
        close(fis);
        close(fos);
    }
}
  
private static void close(Closeable closable) {
    if (closable != null) {
        try {
            closable.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

上述代码对于异常处理十分复杂，
对于资源的关闭也很麻烦，那么可以和下面的进行对比：
private static void customBufferStreamCopy(File source, File target) {
    try (InputStream fis = new FileInputStream(source);
        OutputStream fos = new FileOutputStream(target)){
  
        byte[] buf = new byte[8192];
  
        int i;
        while ((i = fis.read(buf)) != -1) {
            fos.write(buf, 0, i);
        }
    }
    catch (Exception e) {
        e.printStackTrace();
    }
}

用到了这种 try-with-resources 资源自动释放特性。

结束后资源也自动的关闭，释放掉了。就没有必要写出手动的关闭