输入输出流的抽象基类

字节输入流-InputStream

字节输出流-OutputStream

适用场景: 字节流适用读入或者写出二进制文件,如图片,视频,音频等

字符输入流-Reader

字符输出流-Writer

适用场景: 字符流适用读入或者写出文本文件,如txt等

字节输入流

常用的实现类

FileInputStream

BufferedInputStream

ObjectInputStream

字节输出流

常见的实现类

FileOutputStream

BufferedOutputStream

ObjectOutputStream

FileInputStream和FileOutputStream使用示例：

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package pers.xiaotian.ioproject.io;

import java.io.*;

public class StreamTest {

    public static void main(String[] args) {
        InputStream is = null;
        OutputStream os = null;

        try {
            os = new FileOutputStream("byte1.txt");

            int ascii = 65;
            System.out.println((char) ascii);
            os.write(ascii);

            String str = "\n中文";
            os.write(str.getBytes());

            is = new FileInputStream("byte1.txt");
            FileInputStream fis = new FileInputStream("1");
            fis.getChannel();
            System.out.println(is.read());
            System.out.println(is.read());
            System.out.println(is.read());
            System.out.println(is.read());
        } catch (IOException e) {
            throw new RuntimeException(e);
        }finally {
            try {
                is.close();
                os.close();
            } catch (IOException e) {
                throw new RuntimeException(e);
            }

        }
    }
}

ObjectInputStream和ObjectOutputStream使用示例：

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package pers.xiaotian.ioproject.io;

import pers.xiaotian.ioproject.object.Data;

import java.io.*;

public class StreamTest2 {

    public static void main(String[] args) {
        OutputStream os = null;
        InputStream is = null;
        ObjectOutputStream oos = null;
        ObjectInputStream ois = null;
        try {
            os = new FileOutputStream("byte2.txt");
            oos = new ObjectOutputStream(os);

            Data data = new Data();
            data.setDesc("描述信息");
            data.setName("张三");

            Data data1 =new Data();
            data1.setDesc("描述信息1");
            data1.setName("李四");

            oos.writeObject(data);
            oos.writeObject(data1);
            oos.flush();

            FileInputStream is1 = new FileInputStream("byte2.txt");
            ObjectInputStream ois1 = new ObjectInputStream(is1);
            byte[] datas = new byte[2048];
            int len = 0;
            while((len =ois1.read(datas))!=-1){
                System.out.println(new String(datas, 0, len));
            }

            is = new FileInputStream("byte2.txt");
            ois = new ObjectInputStream(is);

            System.out.println(ois.readObject());

        } catch (FileNotFoundException e) {
            throw new RuntimeException(e);
        } catch (IOException e) {
            throw new RuntimeException(e);
        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e);
        }finally {
            try {
                is.close();
                os.close();
                oos.close();
                ois.close();
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
    }
}


BufferedInputStream和BufferedOutputStream使用示例：

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package pers.xiaotian.ioproject.io;

import java.io.*;

public class StreamTest3 {

    public static void main(String[] args) {
        InputStream is = null;
        OutputStream os = null;
        BufferedOutputStream bos = null;
        BufferedInputStream bis = null;

        try {
            os = new FileOutputStream("byte3.txt");
            is = new FileInputStream("byte3.txt");

            //将数据写入到缓冲区管道，提升输入输出IO流的性能
            bos = new BufferedOutputStream(os);
            String str = "asfuashdfha阿花复读啊好烦的安抚爱上发送到插上发爱上对方爱上发";
            bos.write(str.getBytes());
            bos.flush();
            byte[] ins = new byte[1024];
            bis = new BufferedInputStream(is);
            int len = 0;
            while ((len = bis.read(ins)) != -1){
                System.out.println(new String(ins,0, len));
            }
        } catch (FileNotFoundException e) {
            throw new RuntimeException(e);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }finally {
            try {
                is.close();
                os.close();
                bos.close();
                bis.close();
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
    }
}


字符输入流

InputStreamReader

FileReader

BufferedReader

字符输出流

OutputStreamWriter

FileWriter

BufferedWriter

FileReader和FileWriter使用示例：

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package pers.xiaotian.ioproject.io;

import java.io.*;

public class ReadWriteTest {

    public static void main(String[] args) {
        Writer writer = null;
        Reader reader = null;

        try {
            writer = new FileWriter("char1.txt");
            reader = new FileReader("char1.txt");
            String str = "字符写出";
            writer.write(str);
            writer.flush();

            char[] chars = new char[1024];
            int len;
            while((len = reader.read(chars))!=-1){
                System.out.println(new String(chars,0, len));
            }

        } catch (IOException e) {
            throw new RuntimeException(e);
        }finally {
            try {
                writer.close();
                reader.close();
            } catch (IOException e) {
                throw new RuntimeException(e);
            }

        }

    }
}


InputStreamReader和OutputStreamWriter使用示例：

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package pers.xiaotian.ioproject.io;

import java.io.*;

public class ReadWriteTest2 {

    public static void main(String[] args) {
        Reader reader = null;
        Writer writer = null;
        InputStream is = null;
        OutputStream os = null;

        try {
            os = new FileOutputStream("char2.txt");
            writer = new OutputStreamWriter(os);
            writer.write("写入字符串3");
            writer.flush();
            is = new FileInputStream("char2.txt");
            reader = new InputStreamReader(is);
            char[] chars = new char["写入字符串3".length()];
            int len;
            while((len = reader.read(chars))!= -1){
                System.out.println(new String(chars, 0, len));
            }
        } catch (FileNotFoundException e) {
            throw new RuntimeException(e);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }finally {
            try {
                reader.close();
                writer.close();
                is.close();
                os.close();
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }

    }
}



BufferedReader和BufferedWriter使用示例：

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package pers.xiaotian.ioproject.io;

import java.io.*;

public class ReadWriteTest3 {
    public static void main(String[] args) {
        Reader reader = null;
        Writer writer = null;

        //缓冲区的字符输入输出流，传输性能较高
        BufferedWriter bw = null;
        BufferedReader br = null;

        try {
            writer = new FileWriter("char3.txt");
            bw = new BufferedWriter(writer);
            bw.write("字符串写入缓冲区");
            bw.flush();

            reader = new FileReader("char3.txt");
            br = new BufferedReader(reader);
            System.out.println(br.readLine());


        } catch (IOException e) {
            throw new RuntimeException(e);
        }finally {
            try {
                reader.close();
                writer.close();
                bw.close();
                br.close();
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }

    }
}




spring项目,需要获取resoutce目录下的文件可以使用以下方法获取:

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InputStream file = this.getClass().getClassLoader().getResourceAsStream("testData.xlsx");

将输入的文件流转换成MultipartFile可以使用下面方法

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MultipartFile multipartFile = new MockMultipartFile("test.xlsx",
        "test.xlsx", null, file);

参考博客:

https://www.upstudy.top/index.php/archives/23/