java 文件读写工具 FileUtil

代码如下：

 package com.wiscom.utils;

 import java.io.BufferedReader;
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.FileWriter;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.io.Reader;
 import java.io.UnsupportedEncodingException;

 public class FileUtil {

     /**
      *  以字节为单位读取文件，通常用于读取二进制文件，如图片
      * @param path
      * @return
      */
     public static String readByBytes(String path) {
         String content = null;

         try {
             InputStream inputStream = new FileInputStream(path);
             StringBuffer sb = new StringBuffer();
             int c = 0;
             byte[] bytes = new byte[1024];
             /*
              * InputStream.read(byte[] b)
              *
              * Reads some number of bytes from the input stream and stores them into the buffer array b. 从输入流中读取一些字节存入缓冲数组b中
              * The number of bytes actually read is returned as an integer.  返回实际读到的字节数
              * This method blocks until input data is available, end of file is detected, or an exception is thrown.
              * 该方法会一直阻塞，直到输入数据可以得到、或检测到文件结束、或抛出异常  -- 意思是得到数据就返回
              */
             while ((c = inputStream.read(bytes)) != -1) {
                 sb.append(new String(bytes, 0, c, "utf-8"));
             }

             content = sb.toString();
             inputStream.close();
         } catch (FileNotFoundException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }

         return content;
     } 

     /**
      *  以行为单位读取文件，常用于读取面向行的格式化文件
      * @param path
      * @return
      */
     public static String readByLines(String path) {
         String content = null;

         try {
             BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(new FileInputStream(path), "utf-8"));

             StringBuffer sb = new StringBuffer();
             String temp = null;
             while ((temp = bufferedReader.readLine()) != null) {
                 sb.append(temp);
             }

             content = sb.toString();
             bufferedReader.close();
         } catch (UnsupportedEncodingException  e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }

         return content;
     }

     /**
      *  以字符为单位读取文件，常用于读取文本文件
      * @param path
      * @return
      */
     public static String readByChars(String path) {
         String content = null;

         try {

             Reader reader = new InputStreamReader(new FileInputStream(path), "utf-8");
             StringBuffer sb = new StringBuffer();

             char[] tempchars = new char[1024];
             while (reader.read(tempchars) != -1) {
                 sb.append(tempchars);
             }

             content = sb.toString();
             reader.close();
         } catch (Exception e) {
             e.printStackTrace();
         }
         return content;
     }

     /**
      *  把内容content写的path文件中
      * @param content
      * @param path
      * @return
      */
     public static boolean saveAs(String content, String path) {

         FileWriter fw = null;

         //System.out.println("把内容：" + content + "， 写入文件："  + path);

         try {
             /**
              * Constructs a FileWriter object given a File object.
              * If the second argument is true, then bytes will be written to the end of the file rather than the beginning.
              * 根据给定的File对象构造一个FileWriter对象。 如果append参数为true, 则字节将被写入到文件的末尾（向文件中追加内容）
              *
              *    Parameters:
              *        file,  a File object to write to 带写入的文件对象
              *        append,  if true, then bytes will be written to the end of the file rather than the beginning
              *    Throws:
              *        IOException -
              *        if the file exists but is a directory rather than a regular file,
              *            does not exist but cannot be created,
              *            or cannot be opened for any other reason
              *      报异常的3种情况：
              *          file对象是一个存在的目录（不是一个常规文件）
              *          file对象是一个不存在的常规文件，但不能被创建
              *          file对象是一个存在的常规文件，但不能被打开
              *
              */
             fw = new FileWriter(new File(path), false);
             if (content != null) {
                 fw.write(content);
             }
         } catch (IOException e) {
             e.printStackTrace();
             return false;
         } finally {
             if (fw != null) {
                 try {
                     fw.flush();
                     fw.close();
                 } catch (IOException e) {
                     e.printStackTrace();
                 }
             }
         }
         return true;
     }
 }