Java io 文件操作

1、io分类图

 

2、java io基本操作：

    /**
     * 以字节为单位读取文件，常用于读二进制文件，如图片、声音、影像等文件。
     * 一次读一个字节
     * @param fileName
     */
    public static void readFileByBytes(String fileName) {
        try {
            File file = new File(fileName);
            InputStream inputStream = new FileInputStream(file);
            int readByte = 0;
            while ((readByte = inputStream.
                    read()) != -1) {
                System.out.write(readByte);
            }
            inputStream.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

 

/**
     * 以字节为单位读取文件，常用于读二进制文件，如图片、声音、影像等文件。
     * 一次读多个字节
     * @param fileName
     */
    public static void readFileByMoreBytes(String fileName) {
        File file = new File(fileName);
        try {
            InputStream inputStream = new FileInputStream(file);
            byte[] reads = new byte[100];
            int byteread = 0;

            while ((byteread = inputStream.read(reads)) != -1) {
                System.out.write(reads,0,byteread);
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

/**
     * 以字符为单位读取文件，常用于读文本，数字等类型的文件
     * 一次读一字节
     * @param fileName
     */
    public static void readFileByChars(String fileName) {
        File file = new File(fileName);
        try {
            InputStream inputStream = new FileInputStream(file);
            InputStreamReader reader = new InputStreamReader(inputStream);
            int temp = 0;
            while ((temp = reader.read()) != -1) {
//                if ((char)temp != '\r') {
                    System.out.print((char) temp);
//                }
            }
            reader.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

 

/**
     * 以字符为单位读取文件，常用于读文本，数字等类型的文件
     * 一次读多个字节
     * @param fileName
     */
    public static void readFileByMoreChars(String fileName) {
        File file = new File(fileName);
        try {
            InputStreamReader reader = new InputStreamReader(new FileInputStream(file));
            char[] chars = new char[100];
            int temp = 0;
            while ((temp = reader.read(chars)) != -1) {
                if ((temp == chars.length) && (chars[chars.length - 1] != '\r')) {
                    System.out.print(temp);
                } else {
                    for (int i = 0; i < temp; i++) {
                        if (chars[i] != '\r') {
                            System.out.print(chars[i]);
                        } else {
                            continue;
                        }
                    }
                }
            }
            reader.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

 

/**
     * 以行为单位读取文件，常用于读面向行的格式化文件
     * @param fileName
     */
    public static void readFileByLine(String fileName) {
        File file = new File(fileName);
        try {
            BufferedReader bufferedReader = new BufferedReader(new FileReader(file));
            String temp = null;
            int line =1;
            while ((temp = bufferedReader.readLine()) != null) {
                System.out.println("line : " + line + " : " + temp);
                line++;
            }
            bufferedReader.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

 

   /**
     * 随机读取文件内容
     * @param fileName
     */
    public static void readFileByRandomAccess(String fileName) {
        try {
            RandomAccessFile accessFile = new RandomAccessFile(fileName,"r");
            long fileLength =  accessFile.length();
            int beginIndex = fileLength > 10 ? 10 : 0;
            accessFile.seek(beginIndex);
            byte[] bytes = new byte[10];
            int temp = 0;
            while ((temp = accessFile.read(bytes)) != -1) {
                System.out.write(bytes,0,temp);
            }

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

/**
     * 对文件进行追加
     * @param fileName
     * @param content
     */
    public static void appendMethodA(String fileName,String content) {
        try {
            RandomAccessFile accessFile = new RandomAccessFile(fileName,"rw");
            long length = accessFile.length();
            accessFile.seek(length);
            accessFile.write(content.getBytes());
            accessFile.close();

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

    public static void appendMethodB(String fileName,String content) {
        try {
            FileWriter writer = new FileWriter(fileName,true);
            writer.write(content);
            writer.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }