Java将双精度转换为长异常 [英] Java cast double to long exception

问题描述

1- long xValue = someValue;

1- long xValue = someValue;

2- long yValue = someValue;

2- long yValue = someValue;

3- long otherTolalValue =（long）（xValue-yValue）;

3- long otherTolalValue = (long)(xValue - yValue);

该行代码给我以下异常：

That line of code give me the following exception:

java.lang.ClassCastException：java.lang.Double无法转换为java.lang.Long。

• 更新：

代码段：

StackedBarChart<String,Number> sbc = new StackedBarChart<String,Number>();

XYChart.Series<String, Number> series = new XYChart.Series<String, Long>();
series.getData.add(new XYChart.Data<String, Number>("X1",150));
series.getData.add(new XYChart.Data<String, Number>("X2",50));
sbc.getData.add(series);
long dif = getDif(sbc);

long getDif(XYChart barChart){
XYChart.Series series = (XYChart.Series).getData().get(0);
// X1 at zero position i dont have to use iIterator now.
XYChart.Data<String, Long> seriesX1Data = series.getData().get(0);
XYChart.Data<String, Long> seriesX2Data = series.getData().get(1);

long x1Value = seriesX1Data.getYValue();
long x2Value = seriesX1Data.getYValue();
// line - 3 - exception on the next line
// -4- long value = (x1Value) - (x2Value);
long value = (long)(x1Value) - (long)(x2Value);
return value;
}

• 在调试后我发现了。



seriesX1Data，seriesX2Data 包含双值，因为传递的图表具有数字类型但getYvalue（）返回的时间很长，这就是为什么程序在运行时因该异常而崩溃，但是当我强制转换时为什么转换不成功。我认为编译器看到的类型已经很长了！

seriesX1Data,seriesX2Data contains double values as the passed chart has Number type but getYvalue() return long that is why program crash at runtime with that exception but when i cast in line why cast not succeed. i think that compiler see that the type already long !.

推荐答案

不可能

long xValue = someValue;
long yValue = someValue;
long otherTolalValue = (long)(xValue - yValue);

3行均不能产生java.lang.ClassCastException

neither of the 3 lines can produce java.lang.ClassCastException

假设someValue是Double，

Assuming someValues is Double,

Double someValue = 0.0;

会出现编译错误：类型不匹配：无法将Double转换为long

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