从字节流到字符流之Java文件读写

前言

Java文件读写可以分为字节流和字符流，之前一直没有好好归纳以下，借此机会做一个小笔记。

目录

字节流

字节流就是一个字节一个字节的传输，最常用的就是FileInputStream和FileOutputStream，代码如下

 public static void  readByFIS(String filepath) {
        File file = new File(filepath);
        try {
            FileInputStream fis = new FileInputStream(file);
            byte [] bytes = new byte[fis.available()];
            while (fis.read(bytes, 0, bytes.length) != -1) {
                System.out.println(new String(bytes));
            }
            fis.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static void writeByFIS(String filepath) {
        File file = new File(filepath);
        if(!file.exists()) {
            try {
                file.createNewFile();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        try {
            FileOutputStream fos = new FileOutputStream(file, true);
            fos.write("从此无心爱良夜，任他明月下西楼\n".getBytes());
            fos.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

注意在读的的时候我们运用了available去获取一个和文件大小刚好的空间，这存在一个问题，如果文件过大可能会导致内存溢出。

使用BufferedInputStream 和BufferedOutputStream如下

public static void readByBIS(String filepath) {
        File file = new File(filepath);
        if(file.exists()) {
            try {
                BufferedInputStream bis = new BufferedInputStream(new FileInputStream(file));
                byte[] bytes = new byte[bis.available()];
                bis.read(bytes);
                System.out.println(new String(bytes));
                bis.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    public static void writeByBIS(String filepath) {
        File file = new File(filepath);
        if(!file.exists()) {
            try {
                file.createNewFile();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        try {
          BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(filepath));
            bos.write("从此无心爱良夜，任他明月下西楼".getBytes());
            bos.flush();
            bos.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

字符流

运用FileWriter和FileReader

public static void writeByFR(String filepath) {
        File file = new File(filepath);
        if(!file.exists()) {
            try {
                file.createNewFile();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        try {
            FileWriter writer = new FileWriter(filepath, true);
            writer.write("从此无心爱良夜，任他明月下西楼");
            writer.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static void readByFR(String filepath) {
        File file = new File(filepath);
        if(file.exists()) {
            try {
                FileReader reader = new FileReader(file);
                char[] chars = new char[100];
                reader.read(chars);
                System.out.println(chars);
                reader.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

运用BufferedWriter和BufferedReader

ublic static void readByBR(String filepath) {
        File file = new File(filepath);
        String line;
        try {
            BufferedReader reader = new BufferedReader(new FileReader(file));
            while ((line =  reader.readLine()) != null) {
                System.out.println(line);;
            }
            reader.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static void writeByBR(String filepath) {
        File file = new File(filepath);
        if(!file.exists()) {
            try {
                file.createNewFile();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        try {
            BufferedWriter writer = new BufferedWriter(new FileWriter(file, true));
            writer.write("从此无心爱良夜，任他明月下西楼");
            writer.flush();
            writer.newLine();
            writer.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

最后

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