提问人：Andreas Larsen 提问时间：10/21/2022 更新时间：10/21/2022 访问量：32
需要程序每五次输出字符串，而循环已在开关盒中运行
Need program to output string every fifth time while loop has ran withing a switch case
问：
各位程序员大家好。
我有以下代码： public void 命令（） {
boolean runSystem = true;
while (runSystem) {
Scanner sc = new Scanner(System.in);
//int userInput = sc.nextInt();
System.out.println("""
1. Division.
2. Multiplication.
3. Substraction.
4. Addition.
9. Exit program.
Enter command:
""");
try {
switch (sc.nextInt()) {
case 1:
System.out.println("""
You have selected division.
Please enter the first number you wish to divide, then press enter.
Please use comma (,) to seperate periods
""");
double argOneDivision = sc.nextDouble();
System.out.println("Please enter the second number");
double argTwoDivision = sc.nextDouble();
controller.divisionCalc(argOneDivision, argTwoDivision);
System.out.println("We are now dividing " + argOneDivision + " / " + argTwoDivision + " which equeals: ");
System.out.format("%.2f", (controller.divisionCalc(argOneDivision, argTwoDivision)));
System.out.println(" ");
break;
case 2:
System.out.println("""
You have selected multiplciation.
Please enter the first number you wish to divide, then press enter.
Please use comma (,) to seperate periods
""");
double argOneMultiplication = sc.nextDouble();
System.out.println("Please enter the second number");
double argTwoMultiplication = sc.nextDouble();
controller.multiplicationCalc(argOneMultiplication, argTwoMultiplication);
System.out.println("We are now multiplying " + argOneMultiplication + " * " + argTwoMultiplication + " which equeals: ");
System.out.format("%.2f", (controller.multiplicationCalc(argOneMultiplication, argTwoMultiplication)));
System.out.println(" ");
break;
case 3:
System.out.println("""
You have selected substraction.
Please enter the first number you wish to divide, then press enter.
Please use comma (,) to seperate periods.
To indicate it is a minus number, use - at the start of the number.
""");
double argOneSubstraction = sc.nextDouble();
System.out.println("Please enter the second number");
double argTwoSubstraction = sc.nextDouble();
controller.substractionCalc(argOneSubstraction, argTwoSubstraction);
System.out.println("We are now substracting " + argOneSubstraction + " - " + argTwoSubstraction + " which equeals: ");
System.out.format("%.2f", (controller.substractionCalc(argOneSubstraction, argTwoSubstraction)));
System.out.println(" ");
break;
case 4:
System.out.println("""
You have selected addition.
Please enter the first number you wish to divide, then press enter.
Please use comma (,) to seperate periods.
To indicate it is a minus number, use - at the start of the number.
""");
double argOneAddition = sc.nextDouble();
System.out.println("Please enter the second number");
double argTwoAddition = sc.nextDouble();
controller.additionCalc(argOneAddition, argTwoAddition);
System.out.println("We are now substracting " + argOneAddition + " + " + argTwoAddition + " which equeals: ");
System.out.format("%.2f", (controller.additionCalc(argOneAddition, argTwoAddition)));
System.out.println(" ");
break;
case 9:
System.out.println("Closing program");
runSystem = false;
break;
default:
System.out.println("Not a valid option");
controller.checkIfInt();
break;
}
} catch (InputMismatchException e) {
System.out.println("Invalid input. Please read instrucctions clearly.");
}
}
}
}
我希望它每五次输出一个字符串，用户通过终端输入命令。如果能在我的“计算器”课上制作，那就太好了，因为我想确保我遵循 GRASP 原则。
但是，如果它很麻烦，我可以忍受它在“UI”类中，这也是这段代码的来源。
我尝试了一些不同的循环，但出于愤怒而将它们全部删除了._。
希望有人能帮忙。
答：
-1赞
Mushroomator
10/21/2022
#1
既然你关心原理，我就解释一下，什么基本的数学运算能解决每n次做某事的问题。
您希望使用模运算，该运算返回除法的（有符号）余数。Java （和许多其他编程语言）中的模运算符是 .%
例如，如果你计算模数 5：
1 % 5 = 1 6 % 5 = 1
2 % 5 = 2 7 % 5 = 2
3 % 5 = 3 8 % 5 = 3
4 % 5 = 4 9 % 5 = 4
5 % 5 = 0 10 % 5 = 0 <== Every 5-th time modulo returns 0
因此，在您的 Java 程序中，如果您想每 5 次执行一次操作，只需检查模 5 运算是否返回零。
public class Application {
public static void main(String[] args) {
for (var i = 1; i <= 17; i++) {
if(i % 5 == 0) System.out.println("I am a 5-th iteration");
System.out.println(i);
}
}
}
这将打印以下内容：
1
2
3
4
I am a 5-th iteration
5
6
7
8
9
I am a 5-th iteration
10
11
12
13
14
I am a 5-th iteration
15
16
17
使用这个想法，实现你想要的东西应该不难。
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