java读写文件

大家好，又见面了，我是你们的朋友全栈君。

1、一次性读取整个文件内容

/** * 一次性读取全部文件数据 * @param strFile */
    public static void readFile(String strFile){ 
   
        try{ 
   
            InputStream is = new FileInputStream(strFile);
            int iAvail = is.available();
            byte[] bytes = new byte[iAvail];
            is.read(bytes);
            logger.info("文件内容:\n" + new String(bytes));
            is.close();
        }catch(Exception e){ 
   
            e.printStackTrace();
        }
    }

2、字符流按行读取文件

/** * 按行读取文件 * @param strFile */
    public static void readFileByLine(String strFile){ 
   
        try { 
   
            File file = new File(strFile);
            BufferedReader bufferedReader = new BufferedReader(new FileReader(file));
            String strLine = null;
            int lineCount = 1;
            while(null != (strLine = bufferedReader.readLine())){ 
   
                logger.info("第[" + lineCount + "]行数据:[" + strLine + "]");
                lineCount++;
            }
        }catch(Exception e){ 
   
            e.printStackTrace();
        }
    }

3、字节流按行读取文件

 /**
     * 按行读取全部文件数据
     *
     * @param strFile
     */
    public static StringBuffer readFile(String strFile) throws IOException { 
   
        StringBuffer strSb = new StringBuffer();
        InputStreamReader inStrR = new InputStreamReader(new FileInputStream(strFile), "UTF-8");
        // character streams
        BufferedReader br = new BufferedReader(inStrR);
        String line = br.readLine();
        while (line != null) { 
   
            strSb.append(line).append("\r\n");
            line = br.readLine();
        }
        return strSb;
    }

4、写文件

  /**
     * 写入文件
     * @param fileName
     * @param s
     * @throws IOException
     */
    public static void writeToFile(String fileName,String s) throws IOException { 
   
        File f1 = new File(fileName);
        OutputStream out = null;
        BufferedWriter bw = null;
        if (f1.exists()) { 
   
            out = new FileOutputStream(f1);
            bw = new BufferedWriter(new OutputStreamWriter(out, "utf-8"));
            bw.write(s);
            bw.flush();
            bw.close();
        } else { 
   
            System.out.println("文件不存在");
        }
    }

5、写文件，追加内容

/**
     * 追加文件
     */
    public static void writeToFileAppend(String fileName, String text) { 
   
        FileWriter fw = null;
        try { 
   
            //如果文件存在，则追加内容；如果文件不存在，则创建文件
            File f = new File(fileName);
            fw = new FileWriter(f, true);
        } catch (IOException e) { 
   
            e.printStackTrace();
        }
        PrintWriter pw = new PrintWriter(fw);
        pw.println(text);
        pw.flush();
        try { 
   
            fw.flush();
            pw.close();
            fw.close();
        } catch (IOException e) { 
   
            e.printStackTrace();
        }
    }