为什么我的浮点变量保存的是整数？
我已经浏览这段代码有一段时间了，我似乎无法弄清楚可能简单的错误是什么......简而言之，我在Java中有一个浮点变量，它似乎只存储整数内容（整数）实际应有的值。之前，当我将所有内容都塞进一个函数中时，这段代码可以正常工作，但是在我重构代码以使用更多函数后，出现了此错误。这是我到目前为止所得到的：
Java 代码
public class ModifyTimeController extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) {
PopulateTimeIntervals(request.getWriter());
}
protected void PopulateTimeIntervals(PrintWriter writer) {
NumberFormat numberFormat = NumberFormat.getNumberInstance();
numberFormat.setMinimumFractionDigits(2);
numberFormat.setMaximumFractionDigits(2);
float workHours = (float)0.00;
...
/* Code that queries a database for TimeIntervals */
...
while(resultSet.next()) {
// I was told that this type of conversion is
// possible since Timestamp is an extension of Date
Date dtStart = resultSet.getTimestamp("dtStart");
Date dtEnd = resultSet.getTimestamp("dtEnd");
// Accumulates the hours worked in each time interval
workHours += CalculateWorkHours(dtStart, dtEnd);
}
// Should print out something like: 54.27
writer.println(numberFormat.format(workHours).toString());
}
protected float CalculateWorkHours(Date dtStart, Date dtEnd) {
// Divides the difference of the start and end times
// (in miliseconds) by 3600000 to convert to hours
return (dtEnd.getTime() - dtStart.getTime()) / 3600000;
}
}
这已经是漫长的一天了，所以我可能只是错过了一些东西......但是我没有打印出诸如 54.27 小时之类的东西，而是得到了一个固定 54 小时。之前数字格式工作得很好......所以我不知道发生了什么。
I've been glancing at this code for a while now, and I can't seem to figure out what the probably simple error is... In short, I have a float variable in Java that seems to only be storing the integer content (whole number) of what the value is actually supposed to be. I had this bit of code working before when I had everything crammed into one function, but after I re-factored the code to use more functions, this error occurred. Here's what I've got thus far:
Java Code
public class ModifyTimeController extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) {
PopulateTimeIntervals(request.getWriter());
}
protected void PopulateTimeIntervals(PrintWriter writer) {
NumberFormat numberFormat = NumberFormat.getNumberInstance();
numberFormat.setMinimumFractionDigits(2);
numberFormat.setMaximumFractionDigits(2);
float workHours = (float)0.00;
...
/* Code that queries a database for TimeIntervals */
...
while(resultSet.next()) {
// I was told that this type of conversion is
// possible since Timestamp is an extension of Date
Date dtStart = resultSet.getTimestamp("dtStart");
Date dtEnd = resultSet.getTimestamp("dtEnd");
// Accumulates the hours worked in each time interval
workHours += CalculateWorkHours(dtStart, dtEnd);
}
// Should print out something like: 54.27
writer.println(numberFormat.format(workHours).toString());
}
protected float CalculateWorkHours(Date dtStart, Date dtEnd) {
// Divides the difference of the start and end times
// (in miliseconds) by 3600000 to convert to hours
return (dtEnd.getTime() - dtStart.getTime()) / 3600000;
}
}
It's been a long day, so I'm probably just missing something... But rather than printing out something like 54.27 hours, I'm getting a flat 54 hours. The number formatting worked just fine, before... So I don't know what's up.
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在
return (dtEnd.getTime() - dtStart.getTime()) / 3600000;处，您除以一个整数，并使结果成为一个整数。将其更改为3600000.0（或3600000f），您应该会很满意。At
return (dtEnd.getTime() - dtStart.getTime()) / 3600000;you're dividing by an integer, and making the answer an integer. Change it to3600000.0(or3600000f) and you should be golden.这是 long 和 int 的除法，因此结果本身将是 long，然后转换为 float，然后仅保存计算出的 long 值。要获得浮点结果，请先将其中一个操作数强制转换为浮点，或使用浮点文字（如 3600000f）代替。
This is a division of a long and int so the result itself will be a long and then be casted to float which then only holds the computed long value. To get a float result cast one of the operands to float first or use float literal like 3600000f instead.