序列化与文件的输入输出

1.如果要让类能够被序列化，首先需要实现Serializable

import java.io.*;

public class Box implements Serializable {
    
    private int width;
    private int height;

    private transient int id;

    public void setId(int id) {
        this.id = id;
    }

    public void setWidth(int width) {
        this.width = width;
    }

    public void setHeight(int height) {
        this.height = height;
    }
}

2.将序列化对象写入文件

public static void main(String[] args) {
        Box myBox = new Box();
        myBox.setHeight(20);
        myBox.setWidth(50);
        myBox.setId(1);

        try {
          //1.创建存取文件的FileOutputStream对象
            FileOutputStream fs = new FileOutputStream("box.ser");
          //2.创建ObjectOutputStream
            ObjectOutputStream os = new ObjectOutputStream(fs);
          //3.写入对象
            os.writeObject(myBox);
          //4.关闭连接
            os.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
}            

3.解序列化：还原对象

    public static void main(String[] args) {
        try {
            //1.创建FileInputStream ，读取文件
            FileInputStream fileStream = new FileInputStream("box.ser");
            //2.创建ObjectInputStream ，链接FileInputStream 
            ObjectInputStream os = new ObjectInputStream(fileStream);
            //3.读取对象
            Object o = os.readObject();
            //4.转换对象类型
            Box box = (Box) o;
            System.out.println(box.toString());
            //5.关闭ObjectInputStream ，FileInputStream 自动跟着关掉
            os.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }        

 读取文本文件

    public static void main(String[] args) {
        try {
            File myFile = new File("HELP.md");
            //1.FileReader：连接到文本文件的串流
            FileReader fileReader = new FileReader(myFile);
            //2.BufferedReader：将FileReader链接到BufferedReader获取更高效率。
            //BufferedReader只会在缓冲区堵孔的时候才会去磁盘读取
            BufferedReader reader = new BufferedReader(fileReader);

            String line = null;
            while ((line=reader.readLine())!=null){
                System.out.println(line);
            }
            reader.close();
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }