我的条件不起作用，我是初学程序员

Question

double a = 10;// the 10 dollars to spend
double b = 0;// the cost of he food
double c;// final total
double d;// amount of sandwiches
c = a-b;
String Order;
Scanner sc = new Scanner(System.in);

这就是我想要做的，我的目标是获得三明治的数量并乘以它;当数字是2或更低时，她说一件事3或更高的另一件事。问题是它要求我将变量初始化为0，但显然d * 0仍为零。

System.out.println("That'll be 1.06 how many would you like?");
b = 1.06*d;
d = sc.nextDouble();
System.out.println(d <= 2 ?"Ok! Coming right up Sir!":"...Ok.... she     probably thinks you're a fatso now.");
System.out.println("She hands you back "+(a-b)+" as your change");
break;

Answer 1

问题在于：

System.out.println("That'll be 1.06 how many would you like?");
b = 1.06*d;
d = sc.nextDouble();

你还没有初始化d，所以当你进行乘法运算时，你没有任何乘法。在将d相乘之前，您需要将扫描仪的值加载到b。

System.out.println("That'll be 1.06 how many would you like?");
d = sc.nextDouble();
b = 1.06*d;

Answer 2

交换作业的顺序。

b = 1.06*d; // <-- what's d?
d = sc.nextDouble();

像

d = sc.nextDouble();
b = 1.06 * d;

此外，您应该选择更有意义的变量名称。