java学习小工具常量标签

超、凢脫俗 2022-03-18 14:27 165阅读 0赞

###  前言 ###

java开发中使用的一些小工具常量标签：

数据类型转换，时间格式化修改，数组集合转换逗号分隔，高效计数器，排序算法等。

下面贴代码开箱即用：

/**
    	 * 数组变成sql语句中in的数据，例如：'1','2','3'
    	 * 
    	 * @param arr
    	 * @return
    	 */
    	public static String arrToSqlStr(String[] arr) {
    		String result = "";
    		if (arr != null) {
    			for (int i = 0, len = arr.length; i < len; i++) {
    				result += "'" + arr[i] + "',";
    			}
    			if (result.length() > 0) {
    				result = result.substring(0, result.length() - 1);
    			}
    		}
    		return result;
    	}
    
        /**
    	 * 获取百分比
    	 * 
    	 * @param numerator
    	 *            分子
    	 * @param denominator
    	 *            分母
    	 * @return
    	 * @author chenxin
    	 */
    	public static String getPercent(Number numerator, Number denominator) {
    		DecimalFormat df = new DecimalFormat("0.00");
    		if (denominator.doubleValue() == 0) {
    			return df.format(0) + "%";
    		}
    		double percent = numerator.doubleValue() / denominator.doubleValue()
    				* 100;
    		return df.format(percent) + "%";
    	}
    
        /**
         * 类型转换
         * @param num
         * @return
         */
    	public static Number formatInteger(Number num) {
    		if (Math.round(num.doubleValue()) == num.doubleValue()) {
    			return num.intValue();
    		}
    		return num;
    	}
    	/**
    	 * 
    	 * @param num
    	 * @return
    	 */
    	public static Number formatLong(Number num) {
    		if (Math.round(num.doubleValue()) == num.doubleValue()) {
    			return num.longValue();
    		}
    		return num;
    	}
    	/**
    	 * double类型转字符串
    	 * 
    	 * @param num
    	 * @return
    	 */
    	public static String doubleToStr(double num) {
    		DecimalFormat decimalFormat = new DecimalFormat(
    				"###################.###########");
    		return decimalFormat.format(num);
    	}
    
        /**
    	 * 逗号分隔list
    	 * @param fieldList
    	 * @return
    	 */
    	public static String getFieldToSqlstr(List<String> fieldList) {
    		String queryField = "";
    		if (fieldList != null && fieldList.size() > 0) {
    			for (int i = 0, size = fieldList.size(); i < size; i++) {
    				queryField += fieldList.get(i) + ",";
    			}
    			queryField = queryField.substring(0, queryField.length() - 1);
    		}
    		return queryField;
    	}
    
    	/**
    	 * 逗号分隔arr
    	 * @param pointArr
    	 * @return
    	 */
    	public static String arrToSqlStr(int[] pointArr) {
    		String temp = "";
    		if (pointArr != null) {
    			for (int i = 0, size = pointArr.length; i < size; i++) {
    				temp += pointArr[i] + ",";
    			}
    			// 不要最后一个,号字符
    			if (temp.length() > 0) {
    				temp = temp.substring(0, temp.length() - 1);
    			}
    		}
    		return temp;
    	}
    
        /**
    	 * 把list数据变成数组
    	 * 
    	 * @param str
    	 * @return
    	 */
    	public static String[] listToStr(List<String> list) {
    		String[] result = null;
    		if (list != null && list.size() > 0) {
    			result = new String[list.size()];
    			for (int i = 0; i < list.size(); i++) {
    				result[i] = list.get(i);
    			}
    		}
    		return result;
    	}
        
        /**
    	 * 判断是否为整数
    	 * 
    	 * @param str
    	 * @return
    	 */
    	public static boolean checkNumber(String str) {
    		if (str == null) {
    			return false;
    		}
    		Pattern pattern = Pattern.compile("[0-9]*");
    		Matcher matcher = pattern.matcher(str);
    		if (matcher.matches()) {
    			return true;
    		}
    		return false;
    	}
    
        /**
    	 * 判断是否为小数
    	 * 
    	 * @param str
    	 * @return
    	 */
    	public static boolean checkDouble(String str) {
    		if (str == null) {
    			return false;
    		}
    		Pattern pattern = Pattern.compile("[0-9]*(\\.?)[0-9]*");
    		Matcher matcher = pattern.matcher(str);
    		if (matcher.matches()) {
    			return true;
    		}
    		return false;
    	}
    
    	/**
    	 * 冒泡排序 int arr[]={3,30 ,40,10}; 排序后结果 40 30 10 3
    	 * 
    	 * @param arr
    	 * @return
    	 */
    	public static double[] bubbleSort(double[] arr) {
    		double[] result = arr;
    		if (result != null) {
    			int len = result.length;
    			double temp = 0;
    			for (int i = 0; i < len - 1; i++) {
    				for (int j = 0; j < len - i - 1; j++) {
    					if (result[j] < result[j + 1]) {
    						temp = result[j + 1];
    						result[j + 1] = result[j];
    						result[j] = temp;
    					}
    				}
    			}
    		}
    		return result;
    	}
    
    	/**
    	 * 高效计数器
    	 * 
    	 * @param resultList
    	 * @return
    	 */
    	public static HashMap<String, MutableInteger> getMapCount(
    			List<QueryResultBean> resultList) {
    		HashMap<String, MutableInteger> tempMap = new HashMap<String, MutableInteger>();
    		if (resultList != null) {
    			for (int i = 0, size = resultList.size(); i < size; i++) {
    				QueryResultBean tempBean = resultList.get(i);
    				String key = tempBean.getDivId();
    				MutableInteger initValue = new MutableInteger(1);
    				// 利用 HashMap 的put方法弹出旧值的特性
    				MutableInteger oldValue = tempMap.put(key, initValue);
    				if (oldValue != null) {
    					initValue.set(oldValue.get() + 1);
    				}
    			}
    		}
    		return tempMap;
    	}
    
        /**
    	 * 得到网格pts数据
    	 * 
    	 * @param left
    	 * @param right
    	 * @return
    	 */
    	public static Object[] getGridPtsArr(Point2D left, Point2D right) {
    		Object[] pts = null;
    		if (left != null && right != null) {
    			pts = new Object[] { new Object[] {
    					new double[] { left.getY(), left.getX() },
    					new double[] { right.getX(), left.getX() },
    					new double[] { right.getX(), right.getY() },
    					new double[] { left.getY(), right.getY() },
    					new double[] { left.getY(), left.getX() } } };
    		}
    		return pts;
    	}
    
    
        /**
    	 * 得到指定范围的随机数
    	 * 
    	 * @return
    	 */
    	public static double getRandomData() {
    		int max = 1000;
    		int min = 200;
    		float rand = (float) (min + Math.random() * (max - min + 1));
    		return rand / 1000;
    	}
    
        /**
    	 * 格式化给定时间
    	 * @param date
    	 * @param pattern
    	 * @return
    	 */
    	public static String getFormatDate(Date date, String pattern){
    		SimpleDateFormat sdf = new SimpleDateFormat(pattern);
    		return sdf.format(date);
    	}
    
        /**
    	 * 给定时间按指定维度增加后的时间
    	 * @param field	时间维度
    	 * @param date	原始时间
    	 * @param time	变化的时间
    	 * @return
    	 */
    	public static Date getOldDate(int field, Date date, int time){
    		Calendar cal = Calendar.getInstance();
    		cal.setTime(date);
    		cal.add(field, time);
    		return cal.getTime();
    	}
    	
    	/**
    	 * 将 数字的星期几转换成中文的星期几
    	 * @param week
    	 * @return
    	 */
    	public static String getWeekIntToChinese(String sendweek){
    		String week="";
    		try { 
    			if (sendweek != null) {
    				switch (sendweek.toString()) {
    				case "1":
    					week = "一";
    					break;
    				case "2":
    					week = "二";
    					break;
    				case "3":
    					week = "三";
    					break;
    				case "4":
    					week = "四";
    					break;
    				case "5":
    					week = "五";
    					break;
    				case "6":
    					week = "六";
    					break;
    				case "7":
    					week = "日";
    					break;
    				}
    			}
    		} catch (Exception e) {
    			logger.error(e, e);
    		}
    		return week;
    	}
    
         /**
    	  * 判断图片能否打开2
    	  * @return
    	  */
    	 private static BufferedImage read404File(){
    		 String filePath=GatherConstantUtils.imgDirPath+File.separator
    				 +"404.jpg";
    		  File   file = new File( filePath);   
    	      BufferedImage result =null;
    	      try{
    	      result = ImageIO.read(file);
    	      }catch(Exception ex){
    	    	  logger.error(ex,ex);
    	      }
    	      return result;
    	 }
    	 /**
    	   * 判断图片能否打开1
    	   * @param inputFileName
    	   * @return
    	   */
    	  public static BufferedImage readFile(String inputFileName){
    		  BufferedImage result=null; 
    		  try{
    			  if(StringUtils.isEmpty(inputFileName)==true){ 
    				  result=read404File();
    		          return result;   
    			  }
    			  File   file = new File( inputFileName);   
    		      if (!file.exists()) {   
    				  result=read404File();
    		          return result;   
    		      }   
    		      BufferedImage img = ImageIO.read(file); 
    		      if(img==null){
    				  result=read404File();
    		     	 return result;
    		      }
    		      int oldWidth=img.getWidth(null);
    		      // 判断图片格式是否正确   
    		      if (oldWidth== -1) {  
    		          return result;   
    		      } else {   
    		          int newWidth=img.getWidth(null); int newHeight=img.getHeight(null);
    		          if(newWidth>0&&newHeight>0){
    		        	  result=img;
    		          }
    		      }
    		  }catch(Exception ex){
                  logger.error(ex,ex); 
    		  }
    		  return result;
    	  }