java求得字符串中的最长数字串

求得“iou123jk3ui456789kljh23678h”中连续数字串并且返回最长的数字字符串长度

 public static StringBuffer getMaxNum(String str1)
   {
	   int maxLength=0;
	   StringBuffer maxNumBuffer=null;
	   int nowLength=0;
	   StringBuffer nowNumBuffer=null;
	   for(int i=0;i=48 && str1.charAt(i)<=57)
		   {
			   //处理第一个数字字符的时候，用append(c)会报空指针异常
			   if(nowLength==0)
			   {
				   nowNumBuffer=new StringBuffer(String.valueOf(str1.charAt(i)));
				   nowLength++;
			   }
			   else
			   {
				   nowNumBuffer.append(str1.charAt(i));
				   nowLength++;
				   if(nowLength>=maxLength)
				   {
					   maxLength=nowLength;
					   maxNumBuffer=nowNumBuffer;
				   }
			   }
		   }else 
		   {
			   //用于连续数字之后非数字，清楚当前的nowNumBuffer
			  nowLength=0;
			  nowNumBuffer=null;
		   }
	   }
	   return maxNumBuffer;
   }