IO流之字节流知识总结

IO流分为字符流和字节流。

字节流;可以读取任何文件，电脑以字节的方式储存

字符流:用来读取字符。

下面是我总结的思维导图。

相关练习代码

public class Demo {

    @Test
    public void fun() throws IOException {
        FileInputStream fis = new FileInputStream("zzz.txt");
       /* int read = fis.read();//从文件中读取一个字节
        System.out.println(read);
        int read2 = fis.read();//读取下一个
        System.out.println(read2);
        int read3 = fis.read();//读取下一个
        System.out.println(read3);//结果是-1说明文件的结束标记是-1*/

        FileOutputStream fos = new FileOutputStream("xxx.txt");//如果没有文件，会自动创建
        int b;
        while ((b = fis.read()) != -1) {
            fos.write(b);//将字节流写入文件
            System.out.println(b);//通过循环读取
        }

        fis.close();//关闭流
        fos.close();
    }

    //文件的追加
    @Test
    public void fun2() throws IOException {
        FileOutputStream fos = new FileOutputStream("zzz.txt", true);//文件的追加
        fos.write(98);
        fos.write(99);
        fos.close();
    }

    //文件的拷贝一个字节一个字节的拷贝
    @Test
    public void fun3() throws IOException {
        FileInputStream fis = new FileInputStream("592.jpg");//创建输入流
        FileOutputStream fos = new FileOutputStream("make/make/m/2.jpg", true);//输出流
        int b;
        while ((b = fis.read()) != -1) {
            fos.write(b);
        }
        fis.close();
        fos.close();
    }

    //利用字节数组拷贝
    //使用的是available方法获取文件长度
    //大文件都读取到自己数组，内存溢出
    @Test
    public void fun4() throws IOException {
        FileInputStream fis = new FileInputStream("592.jpg");
        FileOutputStream fos = new FileOutputStream("make/make/m/copy.jpg");
        byte[] bytes = new byte[fis.available()];
        fis.read(bytes);
        fos.write(bytes);
        fis.close();
        fos.close();

    }

    //标准小数组文件读取方式
    @Test
    public void fun5() throws IOException {
        FileInputStream fis = new FileInputStream("592.jpg");//输入流
        FileOutputStream fos = new FileOutputStream("make/make/m/copy2.jpg");//输出流
        byte[] bytes = new byte[1024 * 8];//小数组
        int len;
        while ((len = fis.read(bytes)) != -1) {
            fos.write(bytes, 0, len);
        }

        fis.close();
        fos.close();
    }

    //缓冲区文件读写
    @Test
    public void fun6() throws IOException {
        BufferedInputStream bis = new BufferedInputStream(new FileInputStream("592.jpg"));
        BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("make/make/m/copy3.jpg"));
        int len;
        while ((len = bis.read()) != -1) {
            System.out.println(len);
            bos.write(len);
        }

        bis.close();
        bos.close();
    }

    //close方法包含刷新功能，关闭之前先将缓冲区写到文件中
    @Test
    public void fun7() throws IOException {
        BufferedInputStream bis = new BufferedInputStream(new FileInputStream("592.jpg"));
        BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("make/make/m/copy4.jpg"));
        int len;
        while ((len = bis.read()) != -1) {
            bos.write(len);
            bos.flush();//刷新功能
        }
        bis.close();
        bos.close();
    }

    //字节流读写中文
    @Test
    public void fun8() throws IOException {
        FileOutputStream fos = new FileOutputStream("zzz.txt");
        fos.write("你好我是胡少君".getBytes());
        fos.close();
    }

    //标准的异常处理1.6及以前版本
    @Test
    public void fun9() throws IOException {
        FileInputStream fis = null;
        FileOutputStream fos = null;

        try {
            fis = new FileInputStream("xxx.txt");
            fos = new FileOutputStream("zzz.txt");
            byte[] bytes = new byte[1024 * 8];
            int len;
            while ((len = fis.read(bytes)) != -1) {
                fos.write(bytes, 0, len);
            }
        } finally {
            try {
                if (fis != null)
                    fis.close();
            } finally {
                if (fos != null)
                    fos.close();
            }
        }
    }

    //1.7及以上版本
    @Test
    public void fun10() throws IOException {
        try (
                FileInputStream fis = new FileInputStream("xxx.txt");
                FileOutputStream fos = new FileOutputStream("zzz.txt");
        ) {
            byte[] bytes = new byte[1024 * 8];
            int len;
            while ((len = fis.read(bytes)) != -1) {
                fos.write(bytes, 0, len);
            }
        }
    }

    @Test
    public void fun11() throws IOException{

        BufferedInputStream bis=new BufferedInputStream(new FileInputStream("make/make/m/jm.jpg"));
        BufferedOutputStream bos=new BufferedOutputStream(new FileOutputStream("make/make/m/encode.jpg"));
        int len;
        while ((len=bis.read())!=-1){
            bos.write(len^123);//异或两次为本身
        }
        bis.close();
        bos.close();
    }
}