截取字符串中所有的数字字符

   /**
     * 截取字符串中的数字
     * @param s
     * @return
     */
      public static String trimToNumber(String s) {  
          int n = s.length();  
          char[] a = new char[n];  
          int len = 0;  
          for (int i = 0; i < n; i++) {  
              char ch = s.charAt(i);  
              if (Character.isDigit(ch)) {  
                  a[len++] = ch;  
              }  
          }  
          return new String(new String(a, 0, len));  
      }