如果直接输入变量(即(5.00, 20.00),它会完美地计算变化,但如果我用购买和金额替换这些值,它不会计算变化?
public static void makeChange()
{
double purchase;
double tendered;
Scanner scan = new Scanner (System.in);
System.out.println ("How much was the Purchase?");
purchase = scan.nextDouble();
System.out.println ("Amount Tendered");
tendered = scan.nextDouble();
System.out.println("Processing Transaction");
int ch[] = cd.makeChange(purchase, tendered); // does not calculate change correctly
...continued
最佳答案
您正在使用 double
进行算术和比较,一旦任何中间值是无法由 double
精确表示的数字,就会产生不可预测的结果。例如,考虑这个看似无辜的循环:
double value = 1.0;
double dime = 0.1;
while (value > 0) {
value -= dime;
System.out.println(value);
}
打印:
0.9
0.8
0.7000000000000001
0.6000000000000001
0.5000000000000001
0.40000000000000013
0.30000000000000016
0.20000000000000015
0.10000000000000014
1.3877787807814457E-16
-0.09999999999999987
有关为什么会出现这种情况的进一步阅读可以在这里找到:What Every Computer Scientist Should Know About Floating-Point Arithmetic .
正如您在上一个问题中所建议的,将您的 double
变量更改为 BigDecimal
,我认为您的问题将会消失。
关于Java 替换变量,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/11626531/