在执行“longProperty1.divide（longProperty2）”时如何不丢小数位？

I have two LongProperty (there are no decimal places in a long) variables (longProperty1 and longProperty2). I need to divide them and I need to keep the division result in a DoubleProperty (there are decimal places in a double) variable (result) without losing decimal places.

我有两个LongProperty(长整数中没有小数位)变量(longProperty1和longProperty2)。我需要划分它们,我需要将除法结果保存在DoubleProperty(在double中有小数位)变量(result)而不会丢失小数位。

final DoubleProperty result = new SimpleDoubleProperty(0.0);
final LongProperty longProperty1 = new SimpleLongProperty(45);
final LongProperty longProperty2 = new SimpleLongProperty(7);
result.bind(longProperty1.divide(longProperty2));
System.out.println(result.get()); //print: "6.0" instead of "6.428571428571429" (lost decimal places)

longProperty1 and longProperty2 are of type LongProperty because they receive very large numbers, so I can't cast them to DoubleProperties.

longProperty1和longProperty2属于LongProperty类型,因为它们接收的数字非常大,所以我无法将它们转换为DoubleProperties。

On the other hand, the result will receive a value from 0.0 to 1.0 (for example: 0.0, 0.2975, 0.5378, 0.9853, 1.0), because in my real problem longProperty1 <= longProperty2(for example: 500/600=0.8333, 1/2=0.5, 1897/5975=0.3174, ...).

另一方面,结果将从0.0到1.0接收一个值(例如:0.0,0.2975,0.5378,0.9853,1.0),因为在我的实际问题中longProperty1 <= longProperty2(例如:500/600 = 0.8333,1 /2=0.5,1897/5975 = 0.3174,......)。

How to do this?

这该怎么做?

2 个解决方案

#1

The methods provided LongProperty (and by other NumberExpressions) such as divide are convenience methods. You can create a custom binding that does whatever you want:

LongProperty(和其他NumberExpressions)提供的方法如divide是方便的方法。您可以创建一个可以执行任何操作的自定义绑定:

final DoubleProperty result = new SimpleDoubleProperty(0.0);
final LongProperty longProperty1 = new SimpleLongProperty(812323534);
final LongProperty longProperty2 = new SimpleLongProperty(956745323);
result.bind(Bindings.createDoubleBinding(() -> longProperty1.longValue() / (double) longProperty2.longValue(),
    longProperty1, longProperty2));
System.out.println(result.get());
longProperty1.set(612323534);
System.out.println(result.get());

Bindings is a utility class for creating bindings. Here I created a custom binding that returns a double by casting the division of longs to double. You will lose precision here.

Bindings是一个用于创建绑定的实用程序类。在这里,我创建了一个自定义绑定,通过将long的除法转换为double来返回double。你在这里会失去精确度。

The output of the above is:

以上的输出是:

0.8490488685670847
0.6400068223798362

#2

You should use BigDecimal for your calculations.
LongProperty is just a wrapper for usual long value, so no decimal points.

您应该使用BigDecimal进行计算。 LongProperty只是通常长值的包装器,因此没有小数点。

You can try doing longProperty1.divide(longProperty2.doubleValue()) as well, which would call DoubleBinding divide(final double other), but I think this would remove the point of using LongProperty.

您也可以尝试使用longProperty1.divide(longProperty2.doubleValue()),这将调用DoubleBinding除法(最后双倍),但我认为这将删除使用LongProperty的点。

#1