福州新雅图网络科技有限公司2019面试题

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面试时间： 2019-4-19

  1. byte b = (byte) 128;
    答：b为-128
  • byte a = (byte) 127; 127
  • byte b = (byte) 128; -128
  • byte c = (byte) 129; -127
  • byte d = (byte) 130; -126

  1. 使用两种方法遍历map集合

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    public class Demo{
    public static void main(String[] args) {
            Map<Integer, Integer> map = new HashedMap<Integer, Integer>() {
                {
                    put(1, 1);
                    put(2, 2);
                    put(3, 3);
                }
            };
            for (Integer key : map.keySet()) {
                System.out.println(map.get(key));
            }
            for (Map.Entry entry : map.entrySet()) {
                System.out.println(entry.getKey()+" "+entry.getValue());
            }
        }
    }

  2. 将d:\\src下的a.txt文件复制到e:\\src下

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    public class CopyFile {
        public static void main(String[] args) {
            // 方式一
            File file = new File("E:/src/a.mp4");
            File dir = new File("D:/src/");
            if (!dir.exists()) {
                if (!dir.mkdirs()) {
                    throw new RuntimeException("文件夹创建失败");
                } else {
                    if (file.renameTo(new File("D:/src/a.mp4"))) {
                        System.out.println("移动完成！");
                    } else {
                        System.out.println("移动失败！");
                    }
                }
            }
            
            // 方式二
            Path path1 = Paths.get("D:/src/a.mp4");
            Path path2 = Paths.get("E:/src/a.mp4");
            Files.copy(path1, path2, StandardCopyOption.REPLACE_EXISTING);
            
            // 方式三
            ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
            try (FileChannel inChannel = FileChannel.open(Paths.get("D:/src/a.mp4"), StandardOpenOption.READ);
                 FileChannel outChannel = FileChannel.open(Paths.get("E:/src/a.mp4"), StandardOpenOption.CREATE, StandardOpenOption.WRITE)
            ) {
                while (inChannel.read(byteBuffer) != -1) {
                    byteBuffer.flip();
                    outChannel.write(byteBuffer);
                    byteBuffer.clear();
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }