Question

当我运行它时，它会显示案例中的所有System.out.println("")语句。如何让它选择正确的if语句而不是其他内容？

如果我能在找到结果后回到起点，这也会有所帮助。

import java.util.Scanner;
import java.util.Random;

public class TEST {
private static Scanner myScanner;

public static void main(String[] args) {
    myScanner = new Scanner(System.in);
    Random myRandom = new Random();
    int randomNumber;
    char reply;
    System.out.print("Rock(R) Paper(P) or Scissors(S)?  ");
    reply = myScanner.findWithinHorizon(".", 0).charAt(0);
    randomNumber = myRandom.nextInt(3) + 1;
    switch (randomNumber) {
    case 1:
            if (reply == 'S' || reply == 's'); {
            System.out.println("Computer: Rock. You lost!");
            }
            if (reply == 'R' || reply == 'r'); {
            System.out.println("Computer: Rock. You tied!");
            }
            if (reply == 'P' || reply == 'p'); {
            System.out.println("Computer: Rock. You won!");
            break;
            }
    case 2:
            if (reply == 'P' || reply == 'p'); {
            System.out.println("Computer: Paper. You tied!");
            }
            if (reply == 'S' || reply == 's'); {
            System.out.println("Computer: Paper. You won!");
            }
            if (reply == 'R' || reply == 'r'); {
            System.out.println("Computer: Paper. You lost!");
            break;
            }   
    case 3:
            if (reply == 'R' || reply == 'r'); {
            System.out.println("Computer: Scissor. You won!");
            }
            if (reply == 'P' || reply == 'p'); {
            System.out.println("Computer: Scissor. You lost!");
            }
            if (reply == 'S' || reply == 's'); {
            System.out.println("Computer: Scissor. You tied!");
            break;
            }               
        }
    }
}

Answer 1

你有两个问题：

1）你的if语句没有运行，因为它们以分号结尾。这意味着{}中的代码形成一个块并以任何一种方式运行。

2）你的休息是在错误的地方。如果选择'R'（或'r'），第一个只会中断。如果案件运行则后者会中断。

    if (reply == 'P' || reply == 'p'); {
    System.out.println("Computer: Paper. You tied!");
    }
    if (reply == 'S' || reply == 's'); {
    System.out.println("Computer: Paper. You won!");
    }
    if (reply == 'R' || reply == 'r'); {
    System.out.println("Computer: Paper. You lost!");
    break;
    }

VS

    if (reply == 'P' || reply == 'p') {
    System.out.println("Computer: Paper. You tied!");
    }
    if (reply == 'S' || reply == 's') {
    System.out.println("Computer: Paper. You won!");
    }
    if (reply == 'R' || reply == 'r') {
    System.out.println("Computer: Paper. You lost!");
    }
    break;

另外，正如评论中所建议的那样，您可以使用循环来提示输入。例如：

while (! done) {
  System.out.print("Rock(R) Paper(P) or Scissors(S)?  (or Quit(Q) ");
  reply = myScanner.findWithinHorizon(".", 0).charAt(0);
  // more code here
}

这里你需要另一个案例，所以你可以将done设置为true并结束循环。

Answer 2

您使用额外的;

跟踪了if

if语句的语法是：

if(condition){
    Expressions;
}

分号是这样的：

if(condition)
    ; //empty line, effectively ignores the if
{
    Expressions;
}

如果陈述不起作用，Rock Paper Scissor

2 个答案: