用JavaWrite a program that generates 200 random integers between 0 and 9 and displays the count for each number. (Hint: Use an array of ten integers named counts, to store the counts for the number of 0s, 1s, . . . , 9s.)

下面是一个使用Java编写的程序，生成200个在0到9之间的随机整数，并显示每个数字的计数。

import java.util.Random;

public class CountRandomIntegers {
    public static void main(String[] args) {
        int[] counts = new int[10];
        Random rand = new Random();

        for (int i = 0; i < 200; i++) {
            int randomNumber = rand.nextInt(10);
            counts[randomNumber]++;
        }

        for (int i = 0; i < counts.length; i++) {
            System.out.println("Number of " + i + "s: " + counts[i]);
        }
    }
}

这个程序使用了一个名为`counts`的整型数组来存储数字0到9的计数。我们使用`java.util.Random`类生成随机整数，并将它们加入到计数数组中。

在循环结束后，我们遍历计数数组并显示每个数字的计数。

相关问题

Write a program that generates a vector with 30 random integers between –20 and 20 and then finds the sum of all the elements that are divisible by 3.use matlab

Here's the MATLAB code to generate a vector of 30 random integers between -20 and 20, and then find the sum of all the elements that are divisible by 3:

% Generate a vector of 30 random integers between -20 and 20
vec = randi([-20, 20], [1, 30]);

% Find the sum of all the elements that are divisible by 3
divisible_by_3 = mod(vec, 3) == 0;
sum_divisible_by_3 = sum(vec(divisible_by_3));

In the first line, we use the `randi` function to generate a row vector of 30 random integers between -20 and 20. In the second line, we create a logical vector `divisible_by_3` that is true for any element of `vec` that is divisible by 3 (i.e., the remainder after division by 3 is 0). Finally, we use the `sum` function to sum up only the elements of `vec` that are divisible by 3. The result is stored in the variable `sum_divisible_by_3`.

2. (2 points) Please find the dates without any placed order between the time range. (Hint: write a recursive query to create date sequence and use the select statement in Q1 to assign user-defined variables so that you can have a neat recursive query.)

Assuming we have a table `orders` with columns `order_id`, `order_date`, and `customer_id`, we can use the following recursive query to generate a sequence of dates between a specified time range and then find the dates without any placed order:

WITH RECURSIVE dates AS (
  SELECT DATE('2021-01-01') AS date
  UNION ALL
  SELECT date + INTERVAL 1 DAY
  FROM dates
  WHERE date < DATE('2021-12-31')
), orders_count AS (
  SELECT order_date, COUNT(*) AS num_orders
  FROM orders
  WHERE order_date BETWEEN DATE('2021-01-01') AND DATE('2021-12-31')
  GROUP BY order_date
)
SELECT dates.date
FROM dates
LEFT JOIN orders_count ON dates.date = orders_count.order_date
WHERE orders_count.num_orders IS NULL;

In this query, we first define a recursive CTE called `dates` that generates a sequence of dates between `2021-01-01` and `2021-12-31`. Then, we define another CTE called `orders_count` that counts the number of orders for each date between the same time range.

Finally, we join the `dates` CTE with the `orders_count` CTE using a left join and filter for the rows where `num_orders` is null. These are the dates without any placed order.