java开发常用工具类

 package com.rui.util;

 import java.text.DateFormat;
 import java.text.DecimalFormat;
 import java.text.SimpleDateFormat;
 import java.util.Date;
 import java.util.Random;

 /**
  *
  * @ClassName: StrUtils
  * @Description: 工具类
  * @author poseidon
  * @date 2015年10月23日 下午8:13:45
  * @version V1.0.0
  */
 public class StrUtils {

     /**
      *
      * @Title: isEmpty
      * @Description: 空判断
      * @param content
      * @return boolean
      */
     public static boolean isEmpty(String content){
         return (content==null || content.equals(""))?true:false;
     }

     /**
      *
      * @Title: isNotEmpty
      * @Description: 非空判断
      * @param content
      * @return boolean
      */
     public static boolean isNotEmpty(String content){
         return !isEmpty(content);
     }

     /**
      *
      * @Title: formatDate
      * @Description: 格式化日期类
      * @param date
      * @param pattern
      * @return String
      */
     public static String formatDate(Date date,String pattern){
         if(date!=null){
             String dateString = new SimpleDateFormat(pattern).format(date);
             return dateString;
         }else{
             return "";
         }
     }

     /**
      *
      * @Title: getExt
      * @Description: 获取文件的后缀
      * @param name 文件名称
      * @param flag true有点false没点
      * @return String
      */
     public static String getExt(String name,boolean flag){
         if(isNotEmpty(name)){
             String ext  = null;
             if(flag){
                 ext = name.substring(name.lastIndexOf("."), name.length());
             }else{
                 ext = name.substring(name.lastIndexOf(".")+1, name.length());
             }
             return ext;
         }else{
             return "";
         }
     }

     /**
      *
      * @Title: generateFileName
      * @Description: 为上传文件自动分配文件名称，避免重复
      * @param fileName
      * @param randomNum
      * @param dataPattern
      * @return String
      */
     public static String generateFileName(String fileName,int randomNum,String dataPattern) {
         // 获得当前时间
         DateFormat format = new SimpleDateFormat(dataPattern);
         // 转换为字符串
         String formatDate = format.format(new Date());
         // 随机生成文件编号
         int random = new Random().nextInt(randomNum);
         // 获得文件后缀名称
         int position = fileName.lastIndexOf(".");
         String extension = fileName.substring(position);
         // 组成一个新的文件名称
         return formatDate + random + extension;
     }

     /**
      *
      * @Title: countFileSize
      * @Description: 根据File文件的长度统计文件的大小
      * @param fileSize
      * @return String
      */
     public static String countFileSize(long fileSize) {
         String fileSizeString = "";
         try {
             DecimalFormat df = new DecimalFormat("#.00");
             long fileS = fileSize;
             if (fileS == 0) {
                 fileSizeString = "0KB";
             } else if (fileS < 1024) {
                 fileSizeString = df.format((double) fileS) + "B";
             } else if (fileS < 1048576) {
                 fileSizeString = df.format((double) fileS / 1024) + "KB";
             } else if (fileS < 1073741824) {
                 fileSizeString = df
                         .format(((double) fileS / 1024 / 1024) - 0.01)
                         + "MB";
             } else {
                 fileSizeString = df.format((double) fileS / 1024 / 1024 / 1024)
                         + "G";
             }
         } catch (Exception e) {
             e.printStackTrace();
         }
         return fileSizeString;
     }

     /**
      *
      * @Title: conversionSpecialCharacters
      * @Description: 把两个反斜线转换成正斜线
      * @param string
      * @return String
      */
     public static String conversionSpecialCharacters(String string) {
         return string.replaceAll("\\\\", "/");
     }

     public static void main(String[] args) {

     }
 }