Day09字符流&缓冲流&序列化流&IO框架

字符流

FileReader（文件字符输入流）

 使用文件字符输入流，有啥好处？

               读取中文不会出现乱码问题 

FileWriter(文件字符输出流) 

 

利用字符流将一个文本文件复制到E:盘下，例如：D:/1.txt复制到E:/2.txt

请使用字符流：FileReader和FileWriter实现

public class Test {

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


        try ( FileReader fr = new FileReader("D:/1.txt");
              FileWriter fw = new FileWriter("E:/2.txt")){
            char[] chars = new char[3];
            int len;
            while ((len = fr.read(chars)) != -1){

                fw.write(chars);
            }
        }catch (Exception e){
            System.out.println("哈哈哈");
        }


    }
}

字节流、字符流的使用场景小结： 

 1.字节流适合做一切文件数据的拷贝（音视频，文本）；字节流不适合读取中文内容输出。

 2.字符流适合做文本文件的操作（读，写）。

缓冲流 

 字节缓冲流的作用

1.提高字节流读写数据的性能

2.字节缓冲输入流自带了8KB缓冲池；字节缓冲输出流也自带了8KB缓冲池。 

 

public class Demo1 {
    public static void main(String[] args) throws IOException {

        BufferedInputStream bi = new BufferedInputStream(
                new FileInputStream("E:\\QQmusic\\MV\\赵雷-少年锦时 (2015湘江音乐节)(高清).mp4"));

        BufferedOutputStream bo = new BufferedOutputStream(
                new FileOutputStream("E:\\QQmusic\\haha\\赵雷-少年锦时 (2015湘江音乐节)(高清).mp4"));

        byte[] a = new byte[1024 * 1024];

        int len;

        while ((len  = bi.read(a)) != -1){

            bo.write(a,0,len);
        }

        bi.close();
        bo.close();
    }
}

 字符缓冲流

 

public class Demo3 {
    public static void main(String[] args) throws IOException {


        BufferedReader br = new BufferedReader( new FileReader("E:/Code191Day/day09/b-3.txt"));

        BufferedWriter bw = new BufferedWriter(new FileWriter("E:/Code191Day/day09/b-4.txt"));

        String a;

        while ((a = br.readLine()) != null){

            bw.write(a);
            bw.newLine();
        }

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

 转换流

为了解决不同编码读取出现乱码问题 

 打印流

打印流可以实现更方便、更高效的打印数据出去，能实现打印啥出去就是啥出去。 

数据流

允许把数据和其类型一并写出去。 

序列化流 

ObjectOutputStream(对象字节输出流) 

 

public class Demo1 {
    public static void main(String[] args) throws IOException, ClassNotFoundException {
        //0. 准备一个Student对象
        Student student = new Student("张三", 18);

        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("E:/Code191Day/day09/c-5.txt"));

        oos.writeObject(student);

        oos.close();

        ObjectInputStream ois = new ObjectInputStream(new FileInputStream("E:/Code191Day/day09/c-5.txt"));

        Student student1 = (Student)ois.readObject();
        System.out.println(student1.getAge());

        ois.close();
    }
}

//学生类
class Student implements Serializable {
    private String name;
    private Integer age;

    public Student() {
    }

    public Student(String name, Integer age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    @Override
    public String
    toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

 如果一次要序列化多个对象咋整?

 

public class Demo2 {
    public static void main(String[] args) throws IOException, ClassNotFoundException {
        //0. 准备一个Student对象的集合
        List students = new ArrayList<>();
        students.add(new Student("张三", 18));
        students.add(new Student("李四", 19));
        students.add(new Student("王五", 20));

        //1. 序列化(f-1.txt)
        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("E:/Code191Day/day09/c-6.txt"));

        oos.writeObject(students);

        oos.close();

        //2. 反序列化(f-1.txt)

        ObjectInputStream ois = new ObjectInputStream(new FileInputStream("E:/Code191Day/day09/c-6.txt"));

        List objects = (ArrayList)ois.readObject();

        objects.stream().forEach(System.out::println);


        ois.close();
    }
}

IO框架