梳理15--流

详细 百度和文档

https://www.cnblogs.com/shitouer/archive/2012/12/19/2823641.html

1. 

2.

3.

is = new FileInputStream("D://a/a/a.txt");
            os = new FileOutputStream("D://a/b/a.txt");

            //装东西的小桶
            byte[] buffer = new byte[1024];
           //byte[] buffer = new byte[1024*20];

int len; while((len = is.read(buffer)) != -1){ //从buffer的0开始，到len结束 os.write(buffer,0,len); }

   /**
     * 拷贝文件
     */
    @Test
    public void copyFile() throws IOException {
        InputStream is = null;
        OutputStream os = null;
        try {
// 1
            is = new FileInputStream("D://a/a/a.txt");
            os = new FileOutputStream("D://a/b/a.txt");

            //装东西的小桶
            byte[] buffer = new byte[1024];
            int len;
            while((len = is.read(buffer)) != -1){
                //从buffer的0开始，到len结束
                os.write(buffer,0,len);
            }

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } finally {
// 2
            if (is != null) {
                try {
                    is.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
//3
            if (os != null) {
                try {
                    os.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

 File file = new File("D://a/a/a.txt");
            long length = file.length();
            //一次20k
            int per = 1024*20;
            //已经拷贝完成的大小
            long completed = 0L;
            long currentProgress = 0L;

            is = new FileInputStream("D://a/a/a.txt");
            os = new FileOutputStream("D://a/b/a.txt");

            //装东西的小桶
            byte[] buffer = new byte[per];
            int len;
            while((len = is.read(buffer)) != -1){
                //从buffer的0开始，到len结束
                os.write(buffer,0,len);
                completed += per;

                //显示进度
                double percent = (((double)completed/(double) length)*100);
                long progress = Math.round(percent);
                if (progress != currentProgress){
                    System.out.println("已经拷贝了："+ progress + "%");
                }
                currentProgress = progress;
            }

4. 读文件

//放一个管道到文件上

//整一个缓冲

//写出去

 /**
     * 读文件
     * @throws Exception
     */
    @Test
    public void readFile() throws Exception {
        InputStream is = new FileInputStream("D://a.txt");
        byte[] buffer = new byte[1024];
        int len;
        while((len = is.read(buffer)) != -1){
            String s = new String(buffer, 0,len);
            System.out.println(s);
        }

        is.close();
    }

    /**
     * 读文件
     * @throws Exception
     */
    @Test
    public void readFile() throws Exception {
        Reader reader = new FileReader("D://a.txt");
        char[] buffer = new char[1024];
        int len;
        while((len = reader.read(buffer)) != -1){
            String s = new String(buffer, 0,len);
            System.out.println(s);
        }

        reader.close();
    }

字节流可以处理任何字符流的东西。

    /**
     * 读文件
     * @throws Exception
     */
    @Test
    public void readFile() throws Exception {
        Reader reader = new FileReader("D://a.txt");
        BufferedReader bf = new BufferedReader(reader);
        String str;
        while ((str = bf.readLine()) != null){
            System.out.println(str);
        }
        reader.close();
    }

处理流 一行一行的读

5. 写文件

 @Test
    public void writeFile() throws Exception{
        //放一个管道到文件上
        FileOutputStream fo = new FileOutputStream("D://a.txt");
        String str = "hello World";

        //写出去
        fo.write(str.getBytes(StandardCharsets.UTF_8));

        fo.flush();
        fo.close();
    }

@Test
    public void writeFile() throws Exception{
        //放一个管道到文件上
        FileWriter fw = new FileWriter("D://a.txt");
        String str = "hello World";

        //写出去
        fw.write(str);

        fw.flush();
        fw.close();
    }

fw.append("aa").append("bb");