java - 我该如何正确表达呢？使用 && 和 ||首次

Question

我从来没有用过&&或||在我之前的课上，我完全不知道如何正确使用它们。在我看来，我在想像下面这样的东西会起作用，但它没有。

public class ScoreDice {
    // TODO - write your code below this comment.
    // You will need to write one method: scoreWithNumbers.
    // scoreWithNumbers returns a score based on the values
    // of its inputs, as such:
    //
    // - If both inputs are 1 or if both inputs are 6, then
    //   the returned score is 10
    // - If both inputs are the same (but not 1 or 6), then
    //   the returned score is 8
    // - If the inputs are different, the score is whatever the
    //   smaller value is (e.g., if given 3 and 4, it returns 3).
    //
    public static String scoreWithNumbers(int num1, int num2) {
        if ((num1==6 && num2==6) || (num2==1 && num1==1)) {
            return "10";
        } else if ((1 < num1 || num1 < 6) && num2==num1) {
            return "8";
        }
    } 

    public static int scoreWithSeed(long seed) {
        Random random = new Random(seed);
        int num1 = rollD6(random);
        int num2 = rollD6(random);
        return scoreWithNumbers(num1, num2);
    }

    public static int rollD6(Random random) {
        // random.nextInt(6) returns a number between
        // 0 and 5, inclusive.  We want to simulate rolling
        // a D6 (6-sided die) so we add one to this result.
        return random.nextInt(6) + 1;
    }

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.print("Enter seed: ");
        long seed = input.nextLong();
        System.out.println("Score: " + scoreWithSeed(seed));
    }
}

Answer 1

尝试使用下面的代码，注释解释 if 语句的每一步发生的事情:

基本上我改变的是我确保你返回 int's 因为 TODO 没有说 scoreWithNumbers 应该返回字符串，同样我添加了获取两个不同数字的代码并将类型从 long 到 int 因为 int 更适合你程序的 scoreWithNumbers() 部分的相关测试。

import java.util.Scanner;

public class ScoreDice {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter first input number: ");
        int firstInputInt = scanner.nextInt();
        System.out.print("Enter second input number: ");
        int secondInputInt = scanner.nextInt();
        System.out.println("Returned score from the method scoreWithNumbers: " + scoreWithNumbers(firstInputInt, secondInputInt));
    }

    public static int scoreWithNumbers(int num1, int num2) {
        // If both inputs are 1 or if both inputs are 6, then the returned score is 10
        if ((num1==1 && num2==1) || (num1==6 && num2==6)) {
            return 10;
        // If both inputs are the same (but not 1 or 6 [we checked that above]), then the returned score is 8
        } else if (num1 == num2) {
            return 8;
        // If the inputs are different (i.e if (num1 != num2)), the score is whatever the smaller value is (e.g., if given 3 and 4, it returns 3).  
        } else {
            return Math.min(num1, num2);
        }
    } 
}

示例用法(案例 1:两个输入均为 1 或者两个输入均为 6)

Enter first input number:  1
Enter second input number:  1
Returned score from the method scoreWithNumbers: 10

Enter first input number:  6
Enter second input number:  6
Returned score from the method scoreWithNumbers: 10

示例用法(案例 2:两个输入相同但不是 1 或 6)

Enter first input number:  4
Enter second input number:  4
Returned score from the method scoreWithNumbers: 8

示例用法(案例 3:两个输入不同)

Enter first input number:  3
Enter second input number:  5
Returned score from the method scoreWithNumbers: 3

N.B. 最后的 else 可以删除，您可以只使用 return Math.min(num1, num2) 因为那部分只有在 if 和 else if block 都没有事先评估的情况下，才会到达代码。