使用FileInputStream读取文件

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;

public class Main {
    public static void main(String[] args) {
        File dir = new File("/tmp/Temp/temp");
        File file = new File("/tmp/Temp/temp/test.txt");
        if (!dir.exists()) {
            dir.mkdir();//新建目录
        }
        if (!file.exists()) {
            try {
                file.createNewFile();//新建文件
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        //读取文件
        try {
            FileInputStream fileInputStream = new FileInputStream(file);
            int num = fileInputStream.read();//一次读取一个字节
            System.out.println(num);
            int contentLength;
            byte[] bytes= new byte[1024];
            String content=null;
            //超过1kb
            while ((contentLength = fileInputStream.read(bytes))!=-1){
                content=new String(bytes,0,contentLength);//转化成字符串
            }
            System.out.println(content);
            fileInputStream.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

 使用FileOutputStream写文件

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.charset.StandardCharsets;

public class FileWriteDemo {
    public static void main(String[] args) {
        try {
            FileOutputStream fileOutputStream = new FileOutputStream("/tmp/Temp/temp/good.txt");
            String msg="weekend";
            byte[] bytes=msg.getBytes(StandardCharsets.UTF_8);
            fileOutputStream.write(bytes,0,bytes.length);//写文件
            fileOutputStream.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

使用BufferedReader和FileReader读取文件

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;

public class BufferReaderDemo {
    public static void main(String[] args) {
        try {
            BufferedReader bufferedReader = new BufferedReader(new FileReader("/tmp/Temp/temp/test.txt"));
//            int read = bufferedReader.read();//再次读取有可能丢失首字母
//            System.out.println(read);
            //按行读取
//            String readLine = null;
//            while ((readLine = bufferedReader.readLine()) != null) {
//                System.out.println(readLine);
//            }
            //读取十个字符
//            char[] chars = new char[10];
//            int length = bufferedReader.read(chars, 0, chars.length);
//            System.out.println(length);
//            System.out.println(new String(chars,0,length));
            //超过十个字符
//            char[] chars = new char[10];
//            int length=0;
//            while ((length=bufferedReader.read(chars,0,chars.length))!=-1){
//                System.out.println(new String(chars,0,length));
//            }

            bufferedReader.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

使用BufferedWriter和FileWriter写文件

import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;

public class BufferWriterDemo {
    public static void main(String[] args) {
        try {
            BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter("/tmp/Temp/temp/new.txt"));
            bufferedWriter.write("first line");
            bufferedWriter.newLine();//换行
            bufferedWriter.write("second line");
            bufferedWriter.newLine();
            bufferedWriter.flush();//清楚空余
            bufferedWriter.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

使用ObjectOutStream序列化和ObjectInputSstream反序列化

import java.io.*;

public class ObjectDemo {
    public static void main(String[] args) {
//        Student student = new Student("jack",20);
        try {
            //对象的序列化
//            FileOutputStream fileOutputStream = new FileOutputStream("/tmp/Temp/temp/student.bin");
//            ObjectOutputStream objectOutputStream = new ObjectOutputStream(fileOutputStream);
//
//            objectOutputStream.writeObject(student);
//            objectOutputStream.close();
//            fileOutputStream.close();

            //反序列化

            FileInputStream fileInputStream = new FileInputStream("/tmp/Temp/temp/student.bin");
            ObjectInputStream objectInputStream = new ObjectInputStream(fileInputStream);
            Student student = (Student) objectInputStream.readObject();
            System.out.println(student);
            fileInputStream.close();

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