100个Java工具类之22：文件读取和写入工具类

本文主要讲述：文件读取和写入工具类

Java IO流共涉及40多个类，但基类只有四个：

InputStream / Reader ：所有输入流的基类，前者是字节输入流，后者是字符输 入流

OutputStream / Writer ：所有输出流的基类，前者是字节输出流，后者是字符输出 流

一、BufferedReader整行读取

public static String readFile(String filename) {
        File file = new File(filename);
        InputStream is = null;
        Reader reader = null;
        BufferedReader bufferedReader = null;
        StringBuilder result = new StringBuilder();
        try {
            is = new FileInputStream(file);
            reader = new InputStreamReader(is);
            bufferedReader = new BufferedReader(reader);
            String line;
            while ((line = bufferedReader.readLine()) != null) {
                result.append(line);
                result.append("\r\n");
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (null != bufferedReader)
                    bufferedReader.close();
                if (null != reader)
                    reader.close();
                if (null != is)
                    is.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return result.toString();
    }           

二、InputStream字节读取

public static String readFileByChar(String filename) {
        File file = new File(filename);
        InputStream is = null;
        Reader isr = null;
        StringBuilder result = new StringBuilder();
        try {
            is = new FileInputStream(file);
            isr = new InputStreamReader(is);
            int index;

            while (-1 != (index = isr.read())) {
                result.append((char) index);
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (null != is)
                    is.close();
                if (null != isr)
                    isr.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return result.toString();
    }           

三、BufferedWriter写文件

public static void writeByBuffered(String filename, String context) {
        File file = new File(filename);
        FileOutputStream fos = null;
        OutputStreamWriter osw = null;
        BufferedWriter bw = null;
        try {
            if (!file.exists()) {
                file.createNewFile();
            }
            fos = new FileOutputStream(file);
            osw = new OutputStreamWriter(fos);
            bw = new BufferedWriter(osw);
            bw.write(context);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (null != bw) {
                try {
                    bw.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (null != osw) {
                try {
                    osw.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (null != fos) {
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }           

四、OutputStreamWriter写文件

public static void write(String filename, String context) {
        File file = new File(filename);
        FileOutputStream fos = null;
        OutputStreamWriter osw = null;
        try {
            if (!file.exists()) {
                file.createNewFile();
            }
            fos = new FileOutputStream(file);
            osw = new OutputStreamWriter(fos);
            osw.write(context);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (osw != null) {
                try {
                    osw.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (null != fos) {
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }           

本文所有代码都是亲测可试，可直接拿来使用的。

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