mysql double 转string类型转换_java中double类型转换成字符串自动格式化成科学计数法...

/**

* Returns the string representation of the double argument.

*

* The representation is exactly the one returned by the

* Double.toString method of one argument.

*

* @param d a double.

* @return a string representation of the double argument.

* @see java.lang.Double#toString(double)

*/

public static String valueOf(double d) {

return Double.toString(d);

}

而Double自身的toString方法使用FloatingDecimal来对数字进行格式化，代码如下：

public static String toString(double d) {

return new FloatingDecimal(d).toJavaFormatString();

}

该方法注释中写到：

*

If m is less than 10 ^-3 or greater than or

* equal to 10⁷, then it is represented in so-called

* "computerized scientific notation." Let n be the unique

* integer such that 10ⁿ <= m <

* 10ⁿ⁺¹; then let a be the

* mathematically exact quotient of m and

* 10ⁿ so that 1 <= a < 10. The

* magnitude is then represented as the integer part of a,

* as a single decimal digit, followed by '.'

* ('\u002E'), followed by decimal digits

* representing the fractional part of a, followed by the

* letter 'E' ('\u0045'), followed

* by a representation of n as a decimal integer, as

* produced by the method {@link Integer#toString(int)}.

可以很明确的看到，如果数字大于10的7次方或者小于10的-3次方，就会使用科学计数法。这个在很多时候很适用，同时在很多地方也让很多人很头疼。想要避免这个问题，就要自己使用格式化类去重新格式化。最简单的使用DecimalFormat类去格式化，用这个可以很容易的得到不转换成科学计数法的字符串。

DecimalFormat df = new DecimalFormat("###0.0#");//最多保留几位小数，就用几个#，最少位就用0来确定

String s=df.format(d);

这样就可以了~

分享到：

2011-11-23 17:27

浏览 15810

评论