按照以下要求补全①处代码：使其能够运行：This program reads two intergers a and b from user’s input, where 0<a<=b, and finds all the prime number between [a,b) and output the sum of all these prime numbers. import java.util.stream.IntStream; import java.util.Scanner; public class Main { public static void main(String[] args) { Scanner in = new Scanner(System.in); int a = in.nextInt(); int b = in.nextInt(); if ( a<2 ) { a=2; } System.out.println( IntStream.range(a, b). filter(①). sum() ); in.close(); } }

IntStream.range(a, b)
.filter(n -> isPrime(n))
.sum()

在上述代码中，我们使用IntStream的range方法生成一个从a到b-1的整数流。然后使用filter方法来筛选出满足条件的质数，条件可以通过定义一个函数式接口来实现，该接口返回一个布尔值，表示是否为质数。在这里，我们使用isPrime函数来判断一个数是否为质数。最后，使用sum方法对满足条件的质数进行求和，并将结果输出。

相关问题

A perfect number is a number that the sum of all factors (itself excluded) equals itself. For example, 6 is a perfect number because 1+2+3 = 6. This program reads two integers a and b, where 0<a<=b and prints out all the perfect numbers between [a,b). i

以下是Java语言的实现：

import java.util.Scanner;

public class PerfectNumber {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter two integers a and b (0 < a <= b): ");
        int a = sc.nextInt();
        int b = sc.nextInt();
        sc.close();

        for (int num = a; num < b; num++) {
            int sum = 0;
            for (int i = 1; i <= num / 2; i++) {
                if (num % i == 0) {
                    sum += i;
                }
            }
            if (sum == num) {
                System.out.println(num);
            }
        }
    }
}

解释：

1. 首先，我们使用 `Scanner` 类读取用户输入的两个整数 `a` 和 `b`。

2. 接着，我们使用 `for` 循环遍历从 `a` 到 `b` 之间的所有整数。

3. 在循环中，我们定义一个变量 `sum` 来保存当前整数的因子之和，并使用一个嵌套的 `for` 循环来计算该和。具体来说，内部循环从 1 开始遍历到当前整数的一半（因为一个整数的因子最大不会超过它的一半），如果发现一个因子，就把它加到 `sum` 中。

4. 最后，我们判断 `sum` 是否等于当前整数，如果是则输出该数，即为完全数。

注意：题目要求输出所有在区间 [a,b) 内的完全数，因此在循环中使用的是小于 `<` 而不是小于等于 `<=`。

Write a program that reads an expression in a line as input and prints out the result. Only integers and operators below are allowed in the expression:

Sure, I can help you with that! Here is a Python code snippet that can evaluate simple arithmetic expressions containing only integers and the operators +, -, *, and /:

expression = input("Enter an arithmetic expression: ")
result = eval(expression)
print("Result:", result)

You can copy and paste this code into a Python IDE or a Jupyter notebook and execute it. When prompted, enter an arithmetic expression like "2+3*4" and press Enter. The program will then evaluate the expression and print out the result, which in this case should be 14.

Note that the `eval()` function is used to evaluate the expression entered by the user as a Python expression. This means that the user can potentially enter any valid Python expression, so you should be careful when using this function in a production environment.