我的Java代码应让用户输入一个数字,然后计算该数字的阶乘,因此我需要使用“ for循环”。当我输入数字5时,它告诉我阶乘为6,应为120。尝试观看带分解循环的教程,但它们无法正常工作,我认为这是因为我有“ do”命令,该命令从调用中获取值
代码如下:
static Scanner kboard = new Scanner(System.in); //variable to read in values
public static void main(String[] args) {
int choice = 0;
String dummy = "";
String forename = "";
String surname = "";
int number = 0;
do {
System.out.println("1. display the user name, 2. calculate factorial, 3. exit");
choice = kboard.nextInt();
dummy = kboard.nextLine(); //strips out the return
if (choice == 1) {
forename = getforename();
surname = getsurname();
displaydetails(forename, surname);
}
if (choice == 2) {
number = getnumber();
calcfactorial(number);
}
if (choice == 3) {
System.out.println("bye");
}
} while (choice != 3);
}
public static String getforename() {
String newforename = "";
System.out.println("Please enter your forename ?");
newforename = kboard.next();
return (newforename);
} // end getforename
public static String getsurname() {
/*
Code to prompt the user to enter a surname
*/
String newsurname = "";
System.out.println("Please enter your surname ?");
newsurname = kboard.next();
return (newsurname);
} // end getsurname
public static void displaydetails(String displayforename, String displaysurname) {
/*
Code will carry out prescribed changes and display the result
*/
char displayinitial;
String displayusername = "";
displaysurname = displaysurname.toUpperCase();
displayinitial = displayforename.charAt(0);
displayusername = displayinitial + displaysurname;
System.out.println("Your username is " + displayusername);
}
public static int getnumber() {
System.out.println("What numbers factorial do you want to know?");
int newnumber = kboard.nextInt();
return newnumber;
}
public static void calcfactorial(int newnumber) {
int count = 0;
int factorial = 1;
if (newnumber > 0) {
for (count = 1; count <= newnumber; count++); {
factorial = factorial * count;
System.out.println("Factorial of " + newnumber + " is: " + factorial);
}
} else {
System.out.println("Number must be positive");
}
}
答案 0 :(得分:6)
如果您使用过调试器,那么您可以说它只在calcfactorial
方法中执行乘法,并且此时count
已经是6
。原因:
首先,在for
条件循环的末尾删除分号。它充当for
循环的主体。这使count
等于newnumber + 1
或6
。
第二,将打印语句移动到for
循环结束之后,但仍在if
块内。否则,您将获得newnumber
行打印输出。
答案 1 :(得分:-1)
我不会完全放弃答案...用户azurefrog发布了有关调试代码的有用链接。
但是,您的for循环正在执行您不想要的事情:
public static void calcfactorial(int newnumber)
{
int count = 0;
int factorial = 1;
if (newnumber > 0)
{
for (count=1;count<=newnumber;count++);
{
factorial = factorial * count; System.out.println("Factorial of "+newnumber+" is: "+factorial);
}
}
else
{
System.out.println("Number must be positive");
}
}
通读此行,factorial = factorial * count;
行将针对输入的任何要进行阶乘计算的内容执行1 * 1、1 * 2、1 * 3、1 * 4、1 * 5等。 。这不是正确的逻辑。
我建议仔细考虑for
循环的逻辑。您应该在该循环中的某处使用输入的数字(例如,给出的示例为5)。