输入输出流实现文件的拷贝

package com.ydlclass.feature;

import org.junit.Test;

import java.io.*;

public class IOTest {
    String tarPath;

    public String getTarPath() {
        return tarPath;
    }

    public void setTarPath(String tarPath) {
        this.tarPath = tarPath;
    }

    //文件流的使用步骤,例如读取a.t
    @Test
    public void testRead1() throws FileNotFoundException {
        String path = "E:\\元气壁纸缓存\\img_cache\\a.txt";
        File file = new File(path);
        FileInputStream fileInputStream = new FileInputStream(file);//使用一个文件输入流，对接到文件上面去
        int read;
        int i = 0;
        byte[] bytes = new byte[10];
        try {
            while ((read = fileInputStream.read()) != -1){
                byte b = (byte)read;
                bytes[i] = b;
                i++;
            }
            System.out.println(new String(bytes));

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

    @Test
    //第二个read方法的使用以及返回值的含义,参数中需要一个byte数组保存起来；返回值是读取的字节个数
    public void testRead2() throws IOException {
        String path = "E:\\元气壁纸缓存\\img_cache\\a.txt";
        File file = new File(path);
        InputStream inputStream = new FileInputStream(file);
        byte[] bytes = new byte[10];
        int read;
        while ((read = inputStream.read(bytes)) != -1){
            System.out.println(new String(bytes,0,bytes.length - 1));//使用这种方式避免字符串之后的为乱码
        }

        //替换掉上面的内容


        //String path1 = "E:\\元气壁纸缓存\\img_cache\\a.txt";
        //File file1 = new File(path);
        //InputStream inputStream1 = new FileInputStream(file);
        //byte[] bytes1 = new byte[10];
        //int read1;
        //StringBuilder sb = new StringBuilder();
        //while ((read1 = inputStream.read(bytes)) != -1){
        //    //每次读出多少个字节，就将多少个字节变为字符串
        //    String s = new String(bytes,0,read1);
        //    sb.append(s);
        //}
        //System.out.println(sb);
    }


    @Test
    public void testOutput() throws IOException {
        byte[] bytes = {65,66,67};
        //FileOutputStream这个构造器有重载方法，这个重载方***填入一个布尔值，
        // 不加true,则默认覆盖追加至文件的，false则会覆盖源文件内容
        OutputStream outputStream = new FileOutputStream("E:\\元气壁纸缓存" +
                "\\img_cache\\a.txt",false);


        //制定向哪个文件输出
        //outputStream.write(65);//输出的内容为byte类型的值A
        //outputStream.write("hello world!".getBytes());
        //
        outputStream.write(bytes);
    }

    @Test
    //尝试将一个mv视频文件使用io流的方式从磁盘复制到指定的磁盘目录下
    public void testCopyFile() throws IOException {
        //首先使用输入流将文件读入到内存中
        //使用此函数找出哪些是mv文件
        //String PathOfFiles = findMvFiles("E:\\CloudMusic");
        //System.out.println(PathOfFiles);
        //InputStream inputStream = new FileInputStream(new File("E:\\CloudMusic\\MV\\焦迈奇 - 我的名字.mp4"));
        //byte[] bytes = new byte[9000000];
        //inputStream.read(bytes);
        //
        ////将mv文件输出至制定的目录中
        //File tempfile = new File("E:\\CloudMusic\\skin\\temp.mp4");
        //boolean exists = tempfile.exists();
        //if(!exists){//创建一个临时mp4文件
        //    tempfile.createNewFile();
        //}
        //OutputStream outputStream = new FileOutputStream(tempfile.getAbsolutePath());
        //outputStream.write(bytes);



        //InputStream inputStream = new FileInputStream("E:\\CloudMusic\\MV\\焦迈奇 - 我的名字.mp4");
        //File file = new File("E:\\CloudMusic\\MV\\new.mp4");
        //if (!file.exists()){
        //    file.createNewFile();
        //}
        //OutputStream outputStream = new FileOutputStream("E:\\CloudMusic\\MV\\new.mp4");
        //long start = System.currentTimeMillis();
        //int b;
        //while ((b = inputStream.read()) != -1){
        //    outputStream.write(b);
        //}
        //long end = System.currentTimeMillis();
        //System.out.println("单字节搬运：+" + (end - start));



        InputStream inputStream = new FileInputStream("E:\\CloudMusic\\MV\\焦迈奇 - 我的名字.mp4");
        File file = new File("E:\\CloudMusic\\MV\\new.mp4");
        if (!file.exists()){
            file.createNewFile();
        }
        OutputStream outputStream = new FileOutputStream("E:\\CloudMusic\\MV\\new.mp4");
        long start = System.currentTimeMillis();
        byte[] bytes = new byte[1024*1024];//将每次运货箱的大小提升；这样只需要进行比较少的i/o操作就可以完成；
        // 如果还想优化新能，那么可以使用多线程；或者使用nio
        
        int len;
        while ((len = inputStream.read(bytes)) != -1){
            outputStream.write(bytes,0,len);
        }
        long end = System.currentTimeMillis();
        System.out.println("单字节搬运：" + (end - start) );
        
        //上面的io是通过一个字节一个字节的读取文件，即使是8m左右大小的文，耗时大概是60分钟，可见io的效率不高；

        //简单的优化


    }

    public String findMvFiles(String path){
        IOTest ioTest = new IOTest();
        File[] files = new File(path).listFiles(new FilenameFilter() {
            @Override
            public boolean accept(File dir, String name) {
                return new File(dir, name).isDirectory() || name.contains("焦迈奇 - 我的名字.mp4");
            }
        });
        if (files == null || files.length == 0){
            return null;
        }
        for (File file : files) {
            if (file.isDirectory()){
                findMvFiles(file.getAbsolutePath());
                //如果是文件夹，那么递归查找文件
            } else{
                System.out.println(file.getName());
                ioTest.setTarPath(file.getAbsolutePath());
            }
        }
        System.out.println(ioTest.getTarPath());
        return ioTest.getTarPath();
    }


}