IO流

最新推荐文章于 2022-01-15 16:53:15 发布

原创最新推荐文章于 2022-01-15 16:53:15 发布 · 206 阅读

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4 篇文章

订阅专栏

一.流分类

1.按流方向：输入流（读），输出流（写）

2.按读取方式：字节流，字符流

二.字节流

1.使用字节流实现文件的拷贝

public class Copy1 {


    public static void main(String[] args) throws IOException {


        FileInputStream fis = null;
        FileOutputStream fos = null;
        try {
            fis = new FileInputStream("E:/a.txt");
            fos = new FileOutputStream("E:/b.txt", true);
            //定义一个字节数组，减少IO次数
            byte[] buff = new byte[1024];
            //表示读取的字节数，如果未读到，返回-1
            int len = 0;
            while ((len = fis.read(buff)) != -1) {
                fos.write(buff, 0, len);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            fis.close();
            fos.close();
        }

    }
}

2.使用缓冲流包装字节流复制文件（缓冲流是一种包装流）

public class Copy1 {


    public static void main(String[] args) throws IOException {


        FileInputStream fis = null;
        FileOutputStream fos = null;

            fis = new FileInputStream("E:/a.txt");
            //使用缓冲流进行包装
            BufferedInputStream bis = new BufferedInputStream(fis, 10000);
            fos = new FileOutputStream("E:/b.txt", true);
            BufferedOutputStream bos = new BufferedOutputStream(fos, 10000);
            //定义一个字节数组，减少IO次数
            byte[] buff = new byte[1024];
            //表示读取的字节数，如果未读到，返回-1
            int len = 0;
            while ((len = bis.read(buff)) != -1) {
                bos.write(buff,0,len);
            }
            bis.close();
            fis.close();
            bos.close();
            fos.close();

    }
}

二.字符流

使用字符流完成文件拷贝

public class Copy2 {
    public static void main(String[] args) throws Exception {

        BufferedReader br = new BufferedReader(new FileReader("E:/a.txt"));
        BufferedWriter bw = new BufferedWriter(new FileWriter("E:/b.txt"));


        //临时字符数组
        char[] buff = new char[512];
        int len = 0;
        while ((len = br.read(buff))!=-1){
            bw.write(buff,0,len);
        }
        bw.flush();
        br.close();
        bw.close();

    }
}

三.转换流

1.转换流的作用：（1）将字节流转换为字符流（从而可以使用字符流的readLine等方法）

（2）设置编码

public class Trans {
    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new FileReader("E:/a.txt"));
        //只有转换流可以设置编码
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter
                        (new FileOutputStream("E:/b.txt"),"utf-8"));
        String str = null;

        while ((str = br.readLine())!=null){
            bw.write(str+"\r\n");
        }

        bw.flush();
        bw.close();
        br.close();
    }
}

四.对象流（实现序列化和可序列化）

public class ObjectStream {

    public static void main(String[] args) throws IOException, ClassNotFoundException {

        //序列化
        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("E:/obj.object"));
        oos.writeObject(new Person("王强", 18));
        oos.close();
        //反序列化
        ObjectInputStream ois = new ObjectInputStream(new FileInputStream("E:/obj.object"));
        Person p = (Person) ois.readObject();
        System.out.println(p.getName()+""+p.getAge());
    }
}

注意：使用transient修饰的变量不会被序列化