docs: public static boolean isNumber(String str) {
  		if (StrUtil.isBlank(str)) {
  			return false;
  		}
  		char[] chars = str.toCharArray();
  		int sz = chars.length;
  		boolean hasExp = false;
  		boolean hasDecPoint = false;
  		boolean allowSigns = false;
  		boolean foundDigit = false;
  		// deal with any possible sign up front
  		int start = (chars[0] == '-') ? 1 : 0;
  		if (sz > start + 1) {
  			if (chars[start] == '0' && chars[start + 1] == 'x') {
  				int i = start + 2;
  				if (i == sz) {
  					return false; // str == "0x"
  				}
  				// checking hex (it can't be anything else)
  				for (; i < chars.length; i++) {
  					if ((chars[i] < '0' || chars[i] > '9') && (chars[i] < 'a' || chars[i] > 'f') && (chars[i] < 'A' || chars[i] > 'F')) {
  						return false;
  					}
  				}
  				return true;
  			}
  		}
  		sz--; // don't want to loop to the last char, check it afterwords
  				// for type qualifiers
  		int i = start;
  		// loop to the next to last char or to the last char if we need another digit to
  		// make a valid number (e.g. chars[0..5] = "1234E")
  		while (i < sz || (i < sz + 1 && allowSigns && !foundDigit)) {
  			if (chars[i] >= '0' && chars[i] <= '9') {
  				foundDigit = true;
  				allowSigns = false;
  
  			} else if (chars[i] == '.') {
  				if (hasDecPoint || hasExp) {
  					// two decimal points or dec in exponent
  					return false;
  				}
  				hasDecPoint = true;
  			} else if (chars[i] == 'e' || chars[i] == 'E') {
  				// we've already taken care of hex.
  				if (hasExp) {
  					// two E's
  					return false;
  				}
  				if (!foundDigit) {
  					return false;
  				}
  				hasExp = true;
  				allowSigns = true;
  			} else if (chars[i] == '+' || chars[i] == '-') {
  				if (!allowSigns) {
  					return false;
  				}
  				allowSigns = false;
  				foundDigit = false; // we need a digit after the E
  			} else {
  				return false;
  			}
  			i++;
  		}
  		if (i < chars.length) {
  			if (chars[i] >= '0' && chars[i] <= '9') {
  				// no type qualifier, OK
  				return true;
  			}
  			if (chars[i] == 'e' || chars[i] == 'E') {
  				// can't have an E at the last byte
  				return false;
  			}
  			if (chars[i] == '.') {
  				if (hasDecPoint || hasExp) {
  					// two decimal points or dec in exponent
  					return false;
  				}
  				// single trailing decimal point after non-exponent is ok
  				return foundDigit;
  			}
  			if (!allowSigns && (chars[i] == 'd' || chars[i] == 'D' || chars[i] == 'f' || chars[i] == 'F')) {
  				return foundDigit;
  			}
  			if (chars[i] == 'l' || chars[i] == 'L') {
  				// not allowing L with an exponent
  				return foundDigit && !hasExp;
  			}
  			// last character is illegal
  			return false;
  		}
  		// allowSigns is true iff the val ends in 'E'
  		// found digit it to make sure weird stuff like '.' and '1E-' doesn't pass
  		return !allowSigns && foundDigit;
  	}