Question

对于我的编程类，我必须通过使用main方法来处理输入/输出，制作一个计算组合函数C（n，k）= n！/（k！*（nk）！）的程序，计算阶乘的方法，以及计算组合函数的方法。这是我的代码：

import java.util.Scanner;
public class Combinations {

    public static void factorials (int set, int objects) {
        Scanner keyboard = new Scanner(System.in);
        int n = set;
        int k = objects;
        int c = (n-k);
        int factorial1 = 1;
        int factorial2 = 1;
        int factorial3 = 1;
        while (n > 0) {
            factorial1 = factorial1 + s;
            n = n++;
        }//while loop
        while (k > 0) {
            factorial2 = factorial2 + o;
            k = k++;
        }//while loop
        while (c > 0) {
            factorial3 = factorial3 + c;
            c = c++;
        }//while loop
        System.out.println(Combinations(factorial1,factorial2,factorial3));
    }//method factorials
    public static int Combinations (int set, int objects, int x){
        int n = set;
        int k = objects;
        int c = x;
        int combination;
        combination = n/(k*c);
        return combination;
    }//method Combinations
    public static void main(String[] args) {
        Scanner keyboard = new Scanner(System.in);
        System.out.println("Enter the number of integers in a set: ");
        int n = keyboard.nextInt();
        System.out.println("Enter the number of objects to be chosen from the set: ");
        int k = keyboard.nextInt();
        System.out.println(factorials(n,k));
    }//method main

}//class

我的问题是我收到System.out.println(factorials(s,o));的错误消息 - “PrintStream类型中的方法println（boolean）不适用于参数（void）”。我不知道为什么会说这个。救命？

Answer 1

在您的代码中，

public static void factorials(int set, int objects)
{
}

返回void。你不能使用void方法 System.out.println(factorials(s, o));

尝试将代码改为

public static int factorials(int set, int objects)
{
}

计算没有方法调用的组合的另一种方法，

        int index, numberOfItems, itemsToBeSelected, combinations;
        int factorial, temp, result;

        Scanner scanner = new Scanner(System.in);
        System.out.println("Number Of Items (n) : ");
        numberOfItems = scanner.nextInt();

        System.out.println("Items to be selected (r): ");
        itemsToBeSelected = scanner.nextInt();


        for (index = 1, factorial = 1; index <= numberOfItems; index++)    /* Calculate (numberOfItems) -> n! */
        {
            factorial = factorial * index;
        }

        for (index = 1, temp = 1; index <= itemsToBeSelected; index++)         /* Calculate (itemsToBeSelected) -> r! */
        {
            temp = temp * index;
        }

        for (index = 1, result = 1; index <= (numberOfItems - itemsToBeSelected); index++) /* Calculate (numberOfItems - itemsToBeSelected) -> (n-r)!*/
        {
            result = result * index;
        }

        combinations = factorial / (temp * result);
        System.out.println("Combinations : " + numberOfItems + "C" + itemsToBeSelected + " : " + combinations);

<强>输出：

Number Of Items (n) : 
8
Items to be selected (r): 
3
Combinations : 8C3 : 56

Answer 2

基本上，您正在将参数传递给println(Object)方法。但是factorials(s,o)会返回一个空格。你可以调用println()或者如果你想使用println(Object)，那么factorials(s,o)应该返回java.lang.Object的后代。

有关进一步理解，请参阅规格：

PrintStream

Java程序计算组合函数

2 个答案: