Java IO系统字符流（Reader/Writer）字节流（InputStream/OutputStream）读写操作心得笔记

最新推荐文章于 2022-08-04 18:53:33 发布

原创最新推荐文章于 2022-08-04 18:53:33 发布 · 382 阅读

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本文深入讲解了IO系统的结构，包括字符流和字节流的读写操作，以及转换流的应用。详细介绍了各种流的使用方法，如StringReader、BufferedReader、FileReader、FileWriter、FileInputStream、BufferedInputStream、FileOutputStream和BufferedReader结合InputStreamReader的使用。

IO系统结构思维导图
在这里插入图片描述
第一部分字符流

1、字符流读String 缓存流常用 (StringReader/BufferedReader)

/**
     * 字符流读String 缓存流  常用
     */
    public static void readFileStringbuf() throws Exception{
        Reader reader = new StringReader("eddydasdsa\r\nddsadsad "); //该构造器是纯文本，如何是路径不会解析文件内容
        BufferedReader buf = new BufferedReader(reader);
        String line = null;
        StringBuilder builder = new StringBuilder("");
        while (null !=(line = buf.readLine())){
            builder.append(line);
        }
        System.out.println(builder.toString());
        buf.close();
        reader.close();
    }

2、字符流读文本文件缓存流常用 (BufferedReader)

/**
     * 字符流读文本文件 缓存流  常用
     */
    public static void readFileSFbuf() throws Exception{
        Reader reader = new FileReader("D:\\file\\text\\test.txt");
        BufferedReader buf = new BufferedReader(reader);
        String line = null;
        StringBuilder builder = new StringBuilder("");
        while (null !=(line = buf.readLine())){
            builder.append(line);
        }
        System.out.println(builder.toString());
        buf.close();
        reader.close();
    }

3、字符流读文本文件 (FileReader)

 /**
     * 字符流读文件
     */
    public static void readFileString() throws Exception{

        Reader reader = new FileReader(new File("D:\\file\\text\\test.txt"));
        char[] chars = new char[1024];
        int len = 0;
        while ((len = reader.read(chars)) != -1){
            String content = new String(chars);
            System.out.println(content);
//            System.out.println(new String(chars,0,len)); //等同
        }
        reader.close();
    }

4、字符流读String (StringReader)

/**
     * 字符流读String
     */
    public static void readFileString1() throws Exception{
        Reader reader = new StringReader("eddydasdsad"); //该构造器是纯文本，如何是路径不会解析文件内容
        char[] chars = new char[1024];
        int len = 0;
        while ((len = reader.read(chars)) != -1){
            String content = new String(chars);
            System.out.println(content);
//            System.out.println(new String(chars,0,len)); //等同
        }
        reader.close();
    }

5、字符流读文本（控制读取长度）(FileReader)

/**
     * 字符流读文本（控制读取长度）
     */
    public static void readFileStringlen() throws Exception{

        Reader reader = new FileReader(new File("D:\\file\\text\\test.txt"));
        char[] chars = new char[3]; //控制一次性读取长度

//        int aa= reader.read(); //读一位
//        System.out.println((char) aa);
        reader.read(chars); //只读前3位
        String content = new String(chars);
        System.out.println(content);
        int len = 0;
        while ((len = reader.read(chars)) != -1){ //流，前面已读的3个不会再读，从第三位重新读
            System.out.println(new String(chars));
//            System.out.println(new String(chars,0,len)); //等同
        }
        reader.close();
    }

6、单写入字符到文本文件(FileWriter)

/**
     * 单纯写内容
     * @throws Exception
     */
    public static void onlyWrite() throws Exception{
        FileWriter fileWriter = new FileWriter("D:\\file\\text\\test.txt");
        String cont = "abcdefgh";
        fileWriter.write(cont);
        fileWriter.flush();
        fileWriter.close();
    }

第二部分字节流

1、字节流读文件缓存流常用(FileInputStream/BufferedInputStream)

/**
     * 字节流读文件 缓存流  常用
     */
    public static void inFileSFbuf() throws Exception{
        InputStream in = new FileInputStream("D:\\file\\text\\test.txt");
        BufferedInputStream buf = new BufferedInputStream(in);
//        BufferedInputStream buf = new BufferedInputStream(in,4); //可指定缓存区大小
        byte[] bytes = new byte[1024]; //每次从buf缓存区读1024个字节
        int len = 0;
        while ((len = buf.read(bytes)) != -1){
            System.out.println(new String(bytes));
        }
        buf.close();
        in.close();
    }

2、字节流读文件 (FileInputStream byte[])

/**
     * 字节流读文件（文本） FileInputStream  byte[]
     */
    public static void readFile1() throws Exception{
//        File file = new File("D:\\file\\text\\test.txt");
//        InputStream in = new FileInputStream(file);
        InputStream in = new FileInputStream("D:\\file\\text\\test.txt");
        byte[] bytes = new byte[1024];
        int len = 0;
        StringBuilder builder = new StringBuilder("");
        while ((len=in.read(bytes))!=-1){
            builder.append(new String(bytes,"utf-8")); //如果通过电脑编辑gb2312
        }
        System.out.println(builder.toString());
        in.close();
    }

3、字节流写文件(FileOutputStream)

/**
     * 字节流写文件
     */
    public static void writeFile() throws Exception{
        OutputStream out = new FileOutputStream("D:\\file\\text\\test.txt");
        String cont = "abcdefgh";
        out.write(cont.getBytes());
        out.flush();
        out.close();
    }

4、字节流拷贝文件（FileInputStream/FileOutputStream）

/**
     * 字节流拷贝文件
     */
    public static void copyFile() throws Exception{
        File file = new File("D:\\file\\text\\copy.txt");
        if(null == file){
            file.createNewFile();
        }
        InputStream in = new FileInputStream("D:\\file\\text\\test.txt");
        OutputStream out = new FileOutputStream(file);
        int len = 0;
        byte[] bytes = new byte[1024];
        while ((len = in.read(bytes)) != -1){
            out.write(bytes);
        }
        out.flush();
        out.close();
        in.close();
    }

第三部分转换流

1、转换流 BufferedReader 读 InputStream 通过InputStreamReader（也是实现Reader）常用

/**
     *  转换流 BufferedReader 读 InputStream 通过InputStreamReader（也是实现Reader）  常用
     */
    public static void test() throws Exception{
        InputStream in = new FileInputStream("D:\\file\\text\\test.txt");
        BufferedReader reader = new BufferedReader(new InputStreamReader(in));
        String line = null;
        StringBuilder builder = new StringBuilder("");
        while (null !=(line = reader.readLine())){
//            System.out.println(line);
            builder.append(line);
        }
        System.out.println(builder.toString());
        reader.close();
        in.close();
    }

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