Java 石头剪刀布

Question

我知道这个 java 任务已经一次又一次地被问到这里，但是我不想复制其他方法（因为似乎有很多方法可以编写这种代码），我宁愿在地雷上得到帮助我可以更容易地理解这些概念。还有，教授应该很容易就能查到我有没有作弊，哈哈。

这段代码没有错误，但它不能像预期的那样工作。输出真的是……随机的。

我觉得我错过了整个代码部分，但我一遍又一遍地阅读我的教科书，似乎无法发现错误的根源。 :|请帮忙！

编辑：我用固定的更改更新了我的帖子。

import java.util.Scanner;

public class RockPaperScissors
{
   public static void main(String[] args)
     {  
      String playerTwo = "";\\to be honest I'm not sure what this is even for

      Scanner keyboard = new Scanner(System.in);
      System.out.println("Lets play rock-paper-scissors! Please enter your move:");

      int Choice = (int) (Math.random()*2);
         if (Choice == 0)
            playerTwo = "ROCK";\\rock = 0
         else if (Choice == 1)
            playerTwo = "PAPER";\\paper = 1
         else if (Choice == 2)
            playerTwo = "SCISSORS";\\scissors = 2

  String playerOne = keyboard.nextLine();     
     playerOne = playerOne.toUpperCase();
        if (playerOne.equals(playerTwo)){
              System.out.println("It's a tie, so nobody wins!");
              }

        if (playerOne.equals("ROCK")){
              if (playerTwo.equals("PAPER")){
                 System.out.println("Your rock got covered by my paper. You lose!");
                 }
              if (playerTwo.equals("SCISSORS")){
                 System.out.println("Your rock smashes my scissors. You win!");
                 }
              }

        if (playerOne.equals("PAPER")){
              if (playerTwo.equals("ROCK")){
                 System.out.println("Your paper covers my rock. You win!");
                 }
              if (playerTwo.equals("SCISSORS")){
                 System.out.println("Your paper got cut by my scissors. You lose!");
                 }
              }

        else if (playerOne.equals("SCISSORS")){
              if (playerTwo.equals("ROCK")){
                 System.out.println("Your scissors got smashed by my rock. You lose!");
                 }
              if (playerTwo.equals("PAPER")){
                 System.out.println("Your scissors cut my paper. You win!");
                 }
              }

            else
                  System.out.println("Error. Please restart and enter either: \"rock\", \"paper\", or \"scissors\".");
   }
}

Answer 1

在我弄清楚你的代码有什么问题之前，这里有一些建议：

Math.round() 不是必需的。如果您要转换为int，那么它会自动四舍五入到最接近的整数。

您应该声明一个具有三种结果的 Enum。然后您可以通过名称而不是数字或字符串来引用它们：

public enum Outcome { ROCK, PAPER, SCISSOR };

现在您可以分配变量并使用 switch 语句：

Outcome player1 = Outcome.ROCK;
// switch statement example
switch (player1) {
    case ROCK:
        // do something
    case PAPER:
        // do something
    case SCISSOR:
        // do something

此外，cmets 使用两个 FORWARD 斜杠，而不是 BACK 斜杠

现在是代码中的 WTF 时刻。这是什么鬼：

if (playerOne.equals("ROCK")){}
              else if (playerTwo.equals("PAPER")){
                 System.out.println("Your rock got covered by my paper. You lose!");
                 }
              else if (playerTwo.equals("SCISSORS")){
                 System.out.println("Your scissors got smashed by my rock. You win!");
                 }

基本上，您只是告诉计算机，如果 playerOne 选择摇滚，则什么也不做。 if语句的语法是这样的：

if (condition) {
     // do something 
}

如果您想在 if 语句中包含多个 if 语句，请执行以下操作：

if (condition) {
    if (condition) { // do something }
    else if (condition) { // do something else if first did not work }
    else { // do something if nothing worked }
}

在您的代码中，您输入了以下内容：

if (condition) {} // this does nothing if condition is true
else if (condition) {...} // if the first if statement is true, this will not be reached
else if (condition) {...} // neither will this!

所以要解决您的问题，您的代码 sn-p 需要如下所示：

if (playerOne.equals("ROCK")) {
              if (playerTwo.equals("PAPER")) {
                 System.out.println("Your rock got covered by my paper. You lose!");
              }
              else if (playerTwo.equals("SCISSORS")) {
                 System.out.println("Your scissors got smashed by my rock. You win!");
              }
} // terminates outer if

如果您还有其他问题，请对此答案发表评论！

Answer 2

我不会为你编写程序，而是指出你的逻辑缺陷。

if (playerOne.equals("ROCK"))**{}** //notice you aren't actually executing any logic here?
     **else** if (playerTwo.equals("PAPER")){ //this line is being called if playerOne does **not** equal rock.
     System.out.println("Your rock got covered by my paper. You lose!");
}

同样的逻辑也适用于您的其他代码块。

相反，它应该类似于

   if (playerOne.equals("ROCK")){
       if (playerTwo.equals("PAPER")){ 
         System.out.println("Your rock got covered by my paper. You lose!");
       }
    }        

Answer 3

if (playerOne.equals("ROCK")){}
              else if (playerTwo.equals("PAPER")){
                 System.out.println("Your rock got covered by my paper. You lose!");
                 }
              else if (playerTwo.equals("SCISSORS")){
                 System.out.println("Your scissors got smashed by my rock. You win!");
                 }

您的条件块没有正确写入。如果某个条件为真，则将执行以下 { } 块。在您的代码中，您正在检查 playerOne 输入的内容，但当输入与“ROCK”匹配时，您什么也没做。该块只是空白。

接下来将检查 else if 条件，（假设 playerTwo.equals("ROCK")) System.out.println("Your rock ....");将仅基于 playerOne 的输入不等于“ROCK”这一事实执行。

您可能需要查看笔记以了解 else if 语句的工作方式和时间。

相反，你想要的是检查 playerOne.equals("ROCK")，然后检查 playerTwo.equals("PAPER") 并做一些事情。

这适用于您检查 playerOne 输入的每种情况。