I/O Stream

四种复制文件方法

代码实现：

/*
数据源：D:\temp\a.mp4
目的地：D:\temp\b.mp4

比较四种复制方法
    FileInputStream一个字节一个字节复制: infinit
    FileInputStream一个字节数组一个字节数组复制: 1400ms
    BufferedInputStream一个字节一个字节复制: 9604ms
    BufferedInputStream一个字节数组一个字节数组复制: 391ms

主语事项：
    字符流不能处理非文本数据
 */
public class CopyDemo1 {
    public static void main(String[] args) {

        /*try (InputStream in = new FileInputStream("D:\\temp\\a.mp4");
             OutputStream out = new FileOutputStream("D:\\temp\\b.mp4")) {
            long start = System.currentTimeMillis();
            // copy1(in, out);
            copy2(in, out);
            long end = System.currentTimeMillis();
            System.out.println((end - start) + "ms");

        } catch (IOException e) {
            e.printStackTrace();
        }*/

        /*try (InputStream in = new BufferedInputStream(new FileInputStream("D:\\temp\\a.mp4"));
             OutputStream out = new BufferedOutputStream(new FileOutputStream("D:\\temp\\b.mp4"))) {
            long start = System.currentTimeMillis();
            // copy1(in, out);
            copy2(in, out);
            long end = System.currentTimeMillis();
            System.out.println((end - start) + "ms");
        } catch (IOException e) {
            e.printStackTrace();
        }*/

        // 用字符流复制文本数据
        /*try (Reader reader = new InputStreamReader(new FileInputStream("a.txt"));
             Writer writer = new OutputStreamWriter(new FileOutputStream("b.txt"), "GBK")) {
            // copy3(reader, writer);
            copy4(reader, writer);
        } catch (IOException e) {
            e.printStackTrace();
        }*/

        /*try (Reader reader = new FileReader("a.txt");
             Writer writer = new FileWriter("b.txt")) {
            // copy3(reader, writer);
            copy4(reader, writer);
        } catch (IOException e) {
            e.printStackTrace();
        }*/

        // 用字符流复制非文本数据
        /*try (Reader reader = new InputStreamReader(new FileInputStream("D:\\temp\\lyf.jpg"));
             Writer writer = new OutputStreamWriter(new FileOutputStream("D:\\temp\\mm.jpg"))) {
            // copy3(reader, writer);
            copy4(reader, writer);
        } catch (IOException e) {
            e.printStackTrace();
        }*/

        try (BufferedReader reader = new BufferedReader(new FileReader("a.txt"));
             BufferedWriter writer = new BufferedWriter(new FileWriter("b.txt"))) {
            copy5(reader, writer);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    // FileInputStream一个字节一个字节复制
    public static void copy1(InputStream in, OutputStream out) throws IOException {
        int data;
        while ((data = in.read()) != -1) {
            out.write(data);
        }
    }

    // FileInputStream一个字节数组一个字节数组复制
    public static void copy2(InputStream in, OutputStream out) throws IOException {
        byte[] bytes = new byte[1024];
        int len;
        while ((len = in.read(bytes)) != -1) {
            out.write(bytes, 0, len);
        }
    }

    // 一个一个字符复制数据
    public static void copy3(Reader reader, Writer writer) throws IOException {
        int data;
        while ((data = reader.read()) != -1) {
            writer.write(data);
        }
    }

    // 一个字符数组一个字符数组复制数据
    public static void copy4(Reader reader, Writer writer) throws IOException {
        char[] chars = new char[1024];
        int len;
        while ((len = reader.read(chars)) != -1) {
            writer.write(chars, 0, len);
        }
    }

    public static void copy5(BufferedReader reader, BufferedWriter writer) throws IOException {
        String s;
        while ((s = reader.readLine()) != null) {
            writer.write(s);
            writer.newLine();
            // writer.flush();
        }
    }
}

---

FileFilter

用于抽象路径名的过滤器。

boolean accept(File pathname)

代码实现：

/*
    获取 D:\\temp 以 .txt 结尾的文件。
 */
public class Test3 {
    public static List<File> search(File src) {
        // 匿名内部类
        File[] files = src.listFiles(new FileFilter() {
            @Override
            public boolean accept(File file) {
                return file.isFile() && file.getName().endsWith(".txt");
            }
        });
        return Arrays.asList(files);
    }

    public static void main(String[] args) {
        File src = new File("D:\\temp");
        List<File> list = search(src);
        for(File f : list) {
            System.out.println(f);
        }
    }
}

---

IO流

IO流：