我如何找到价格的平均值？

Question

我必须将数据存储在二维数组中，然后打印具有可用选项“否”的价格的平均值，任何人都可以帮助找到平均值。

public class Test {
    public static void main(String[] args) {
        double total = 0;
        Products[][] names = new Products[][]{
                {new Products("k7580", 6500, "yes")},
                {new Products("k8570", 7333, "no")},
                {new Products("k8580", 766, "no")},
                {new Products("k6580", 288, "yes")}
        };
        for (int i = 0; i < names.length; i++) {
            for (int j = 0; j < names[i].length; j++) {
                String available = names[i][j].getAvailable();
                if (available.equals("no")) {
                    total = total + names[i][j].getPrice();
                }
            }
            System.out.println("");
        }
        // from here I am not able to find average
        double average = total / names.length;
        System.out.println("average of price :" + average);
    }
}

Answer 1

您需要定义一个count变量，根据您的 if 条件（ available.equals("no") ）每次递增它以仅计算满足条件的元素：

double total = 0;
Products[][] names = new Products[][] { { new Products("k7580", 6500, "yes") },
        { new Products("k8570", 7333, "no") }, { new Products("k8580", 766, "no") },
        { new Products("k6580", 288, "yes") } };

int count = 0;
for (int i = 0; i < names.length; i++) {
    for (int j = 0; j < names[i].length; j++) {
        String available = names[i][j].getAvailable();
        if (available.equals("no")) {
            count++;
            total +=names[i][j].getPrice();
        }
    }
    System.out.println("");
}

// from here I am not able to find average

double average = total / count;
System.out.println("average of price :" + average);

Answer 2

如果您使用Java 8或更高版本，则可以使用它：

public static void main(String[] args) {
    Products[][] names = new Products[][]{
            {new Products("k7580", 6500, "yes")},
            {new Products("k8570", 7333, "no")},
            {new Products("k8580", 766, "no")},
            {new Products("k6580", 288, "yes")}
    };

    Arrays.stream(names)
            .flatMap(array -> Arrays.stream(array))
            .filter(products -> products.getAvailable().equals("no"))
            .mapToDouble(Products::getPrice)
            .average()
            .ifPresent(average -> System.out.println(
                    "average of price: " + average));
}

输出是：

average of price: 4049.5

如您所见，它很简洁。 我在这里使用了流。 Stream 有助于减少代码的冗长。

Answer 3

您不需要定义二维数组，只需维护一维产品数组并维护需要考虑平均的合格商品的数量（在您的情况下不可用的商品）

此代码将在单个循环中运行，无需嵌套循环。

public class Test {
    public static void main(String[] args) {
        double total = 0;
        int notAvailableItems = 0;
        Products[] names = new Products[]{
                new Products("k7580", 6500, "yes"),
                new Products("k8570", 7333, "no"),
                new Products("k8580", 766, "no"),
                new Products("k6580", 288, "yes")};
        for (int i = 0; i < names.length; i++) {
            Products product = names[i];
            if (product.getAvailable().equals("no")) {
                total = total + product.getPrice();
                notAvailableItems++;
            }
        }
        double average = total / (double) notAvailableItems;
        System.out.println("average of price: " + average);
    }
}

输出：

average of price: 4049.5