<div class="s1 swiper-container swiper-container3">
        #set($datas = $dataTool.list("t1,t2", "a1,a2",1))
        #foreach($data in ${datas.datas})

        #set($dataValue = $data.value)
        #set($dataPreValue = $data.preValue)
        #set($Double = 0.00)
        #set($diff = $Double.valueOf($dataValue) - $Double.valueOf($dataPreValue))
    <div class="swiper-wrapper">
        <div class="inner swiper-slide">
            <a href="">
                <h3>${data.name}</h3>
                <div class="c1 value">${data.value}</div>
                <div class="c2">
                        <span id="aaa" class="l fn-diff">$diff</span>
                        <span class="r">${data.raise1}</span>
                </div>
            </a>
        </div>
    </div>
    #end
</div>

上面的例子运行后大概是这样；
diff = value - prevalue
diff = 1 - 0
结果弄出来这样 0.99999999999999999
明显不对，要么怎样让结果变成正确？要么怎样小数点截取到2位；