code: public static String toStr(Number number, String defaultValue) {
  		return (null == number) ? defaultValue : toStr(number);
  	}
docs: 数字转字符串<br>
  调用{@link Number#toString()}，并去除尾小数点儿后多余的0
  
  @param number A Number
  @param defaultValue 如果number参数为{@code null}，返回此默认值
  @return A String.
  @since 3.0.9