Java文件读写

Java提供文件读写操作有很多种，这里介绍几种供参考

字节流

FileInputStream读取文件

public class FileInputStreamDemo {

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

        File file = new File("d:/index.sh");
        if (!file.exists()) {
            throw new RuntimeException("文件不存在");
        }

        FileInputStream fis = new FileInputStream(file);
        int len;
        byte[] buf = new byte[1024];
        while ((len = fis.read(buf)) != -1) {
            System.out.println(new String(buf, 0, len));
        }

        fis.close();
    }

}

FileOutputStream写文件

public class FileOutputStreamDemo {
    public static void main(String[] args) throws IOException {
        File file = new File("d://1.txt");
        try {
            file.createNewFile();
        } catch (IOException e) {
            e.printStackTrace();
        }
        FileOutputStream fileOutputStream = new FileOutputStream(file);
        try (fileOutputStream) {
            String str = "hello world";
            for (int i = 0; i < str.length(); i++) {
                int b = str.charAt(i);
                fileOutputStream.write(b);
            }

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

    }
}

缓冲流使用

BufferedOutputStream

import java.io.BufferedOutputStream;
import java.io.FileOutputStream;
import java.io.IOException;

public class BufferedOutputStreamDemo {
    public static void main(String[] args) throws IOException {
        fileWriter();
    }

    public static void fileWriter() throws IOException {
        FileOutputStream fos = new FileOutputStream("d:/1.txt", true);

        BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(fos);
        try (bufferedOutputStream) {
            byte[] bytes = "hello world".getBytes();
            bufferedOutputStream.write(bytes);
            bufferedOutputStream.flush();
        } catch (Exception e) {
            e.printStackTrace();
        }


    }
}

BufferedOutputStream读取文件

import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.IOException;

public class BufferedInputStreamDemo {
    public static void main(String[] args) throws IOException {
        fileRead();
    }

    private static void fileRead() throws IOException {
        FileInputStream fis = new FileInputStream("d:/1.txt");

        BufferedInputStream bis = new BufferedInputStream(fis);
        try (bis) {
            byte[] buffer = new byte[10240];
            int flag;
            while ((flag = bis.read(buffer)) != -1) {
                System.out.println(new String(buffer, 0, flag));
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

字符缓冲输出流

BufferedWriter写文件

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

public class BufferedWriteDemo {
    public static void main(String[] args) throws IOException {
        method();
    }

    private static void method() throws IOException {
        BufferedWriter bw = new BufferedWriter(new FileWriter("d:/2.txt"));

        try (bw) {
            bw.write("hello world");
            bw.flush();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

BufferedReader读取文件

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

public class BufferedReaderDemo {
    public static void main(String[] args) throws IOException {
        method();
    }

    private static void method() throws IOException {
        BufferedReader br = new BufferedReader(new FileReader("d:/2.txt"));

        String line;
        try (br) {
            while ((line = br.readLine()) != null) {
                System.out.println(line);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

对象流

ObjectOutputStream读取文件

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.io.Serializable;

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Person implements Serializable {

    private String id;

    private String name;

    private Integer age;
}

import java.io.*;


public class ObjectOutputStreamDemo {
    public static void main(String[] args) throws IOException, ClassNotFoundException {
        String fileName3 = "d:/1.txt";
        try(ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(fileName3))) {
            oos.writeObject(new Person("11", "hello", 24));
        }

      
    }
}

ObjectInputStream写文件

import java.io.*;

public class ObjectOutputStreamDemo {
    public static void main(String[] args) throws IOException, ClassNotFoundException {
        String fileName3 = "d:/1.txt";
      

        try(ObjectInputStream ois = new ObjectInputStream(new FileInputStream(fileName3))) {
            Object res = ois.readObject();
            System.out.println(res);
            Object res2 = ois.readObject();
            System.out.println(res2);
        }
    }
}

总结

文件流的读写，看个人擅长以及读写效率，最重要的是，读写完毕之后，记得关闭文件流