Question

我是编程新手，我一直在尝试创建一个简单的Rock Paper Scissors游戏。基本上，它使用while循环并询问用户是否要播放（或继续）。一旦他们不再想要，该计划必须打印出游戏总数，获胜次数，损失次数和获胜百分比。我已经完成了整个计划，除非它总是说胜利的百分比是0.0％，即使它没有。我已经使用了if语句来避免任何除零错误。我没有得到任何运行时或编译器错误，所以我要么丢失了一些东西，要么就是我找不到的逻辑错误。我想继续使用扫描仪。

import java.util.Scanner; 

public class RockPaperScissors {

/*
 * Program allows user to play Rock, Paper and Scissors as many times as desired by entering Y until they enter N.
 * Program will print amount of games played, amount lost, amount won and percentage won. 
 * User must enter "Y", "N", "Rock", "Paper" or "Scissors" with correct capitalization and spelling. 
 */ 

public static void main(String[] args) {

    Scanner input = new Scanner(System.in);

    int playerWins = 0;
    int compWins = 0;
    int gamesPlayed = 0;

    while (true) {
        System.out.println("Do you want to play Rock Paper Scissors (Y/N): ");
        String play = input.nextLine();

        // user terminates game and program prints number of wins, losses and percentage of wins.
        if (play.equals("N")) {

            System.out.println("You played a total of " + gamesPlayed + " matches against the computer");
            System.out.println("The computer won " + compWins + " matches");
            System.out.println("You won " + playerWins + " matches");

            // 0% wins when no games are played.
            if (gamesPlayed == 0) { 
                System.out.println("You won 0% of the time!");
                break;

            } else if (gamesPlayed > 0) {
                double totalWins = (int)(playerWins / gamesPlayed) * 100;
                System.out.println("You won " + totalWins + "% of the time!");
                break;
            }

        } else if ((!play.equals("N")) && (!play.equals("Y"))) {
            System.out.println("Invalid entry");
        } else {

            System.out.println("Welcome to Rock, Paper and Scissors!");
            System.out.print("Select \"Paper\", \"Rock\" or \"Scissors\": ");
            String decision = input.nextLine();
            System.out.println("Your selection: " + decision);

            // random number generator producing integer values between 1 to 3 for computer's choices.
            // 1 is for Rock, 2 is for Paper and 3 is for Scissors.
            int num = (int)(Math.random() *  (3-0) + 1);

            switch (num) {

                // Computer picks Rock
                case 1:
                    if (decision.equals("Rock")) {
                    System.out.println("Tie, you and the computer selected rock");
                    gamesPlayed++;
                } else if (decision.equals("Paper")) {
                    System.out.println("You win, paper beats rock!");
                    gamesPlayed++;
                    playerWins++;
                } else if (decision.equals("Scissors")) {
                    System.out.println("Computer wins, rock beats scissors!");
                    gamesPlayed++;
                    compWins++;
                } else {
                    System.out.println(decision + " is not a valid input");
                }
                break;
                case 2:
                    // computer picks Paper
                    if (decision.equals("Rock")) {
                    System.out.println("Computer wins, rock beats paper!");
                    gamesPlayed++;
                    compWins++;
                } else if (decision.equals("Paper")) {
                    System.out.println("Tie, you and the computer selected paper");
                    gamesPlayed++;
                } else if (decision.equals("Scissors")) {
                    System.out.println("You win, scissors beats paper");
                    gamesPlayed++;
                    playerWins++;
                } else {
                    System.out.println(decision + " is not a valid input");
                }
                break;
                case 3:
                    // computer picks Scissors
                    if (decision.equals("Rock")) {
                    System.out.println("You win, rock beats scissors");
                    gamesPlayed++;
                    playerWins++;
                } else if (decision.equals("Paper")) {
                    System.out.println("Computer wins, scissors beats paper");
                    gamesPlayed++;
                    compWins++;
                } else if (decision.equals("Scissors")) {
                    System.out.println("Tie, you and the computer selected scissors");
                    gamesPlayed++;
                } else {
                    System.out.println(decision + " is not a valid input");
                }
                break;

            } 
        }

    }

}

}

Answer 1

问题发生在double totalWins = (int)(playerWins / gamesPlayed) * 100;。由于playerWins和gamesPlayed都是整数类型（特别是int类型），因此Java正在执行'整数除法'，它返回除法的商作为结果并忽略余数。因此，为了防止它这样做，您最好将该行更改为：

double totalWins = (playerWins * 100.0) / gamesPlayed;
//                 /------------------\
// This converts the `playerWins` to a `double` and does the division as you expect

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