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为课堂做一个项目，我试图用与教授最终做的不同的方式去做。编译时我得到： 

RPSLS.java:65: error: incompatible types: Object cannot be converted to int
  switch (userChoice){
     ^
1 error
错误指向 switch 语句的开头。

import javax.swing.JOptionPane;
import java.util.Random;
public class RPSLS {
  public static void main(String[] args) {

    //Setting choices and compChoice (for the number the computer chooses)
    int compChoice;
    final int Rock = 0;
    final int Paper = 0;
    final int Scissors = 0;
    final int Lizard = 0;
    final int Spock = 0;

    //Comp Choice
    Random generator = new Random();
    compChoice = generator.nextInt(5) + 1;

    //User Choice
    Object[] possibleValues = {
      "Rock", "Paper", "Scissors", "Lizard", "Spock"
    };

    Object userChoice = JOptionPane.showInputDialog(null,
      "Choose one", "Input",
      JOptionPane.INFORMATION_MESSAGE, null,
      possibleValues, possibleValues[0]); //Set the default option (AFIAK it doesn't matter for this kind of thing)

    System.out.println("The computer chose: " + compChoice);
    System.out.println("The computer chose: " + userChoice);

    //Set the userChoice equal to a number based on what was picked in userChoice question after both have entered choices and the choices are printed
    //Values are to be set as follows:
    //Rock 0
    //Paper 1
    //Scissors 2
    //Lizards 3
    //Spock 4
    if (userChoice == "Rock") {
      userChoice = String.valueOf(Rock);
    } else if (userChoice == "Paper") {
      userChoice = String.valueOf(Paper);
    } else if (userChoice == "Scissors") {
      userChoice = String.valueOf(Scissors);
    } else if (userChoice == "Lizard") {
      userChoice = String.valueOf(Lizard);
    } else if (userChoice == "Spock") {
      userChoice = String.valueOf(Spock);
    }





    //Determine who wins
    switch (userChoice) {
      case 0: //User chooses Rock
        if (compChoice == 0) //Rock
        {
          System.out.println("Tie, try again.");
        } else if (compChoice == 1) //Paper
        {
          System.out.println("Computer Win");
        } else if (compChoice == 2) //Scissors
        {
          System.out.println("Player Win");
        } else if (compChoice == 3) //Lizard
        {
          System.out.println("Player Win");
        } else if (compChoice == 4) //Spock
        {
          System.out.println("Computer Win");
        }
        break;


      case 1: //User chooses paper
        if (compChoice == 0) //Rock
        {
          System.out.println("Player Win");
        } else if (compChoice == 1) //Paper
        {
          System.out.println("Tie, try again.");
        } else if (compChoice == 2) //Scissors
        {
          System.out.println("Computer Win");
        } else if (compChoice == 3) //Lizard
        {
          System.out.println("Computer Win");
        } else if (compChoice == 4) //Spock
        {
          System.out.println("Player Win");
        }
        break;


      case 2: //User chooses scissors
        if (compChoice == 0) //Rock
        {
          System.out.println("Computer Win");
        } else if (compChoice == 1) //Paper
        {
          System.out.println("Player Win");
        } else if (compChoice == 2) //Scissors
        {
          System.out.println("Tie, try again.");
        } else if (compChoice == 3) //Lizard
        {
          System.out.println("Player Win");
        } else if (compChoice == 4) //Spock
        {
          System.out.println("Computer Win");
        }
        break;


      case 3: //User chooses lizard
        if (compChoice == 0) //Rock
        {
          System.out.println("Computer Win");
        } else if (compChoice == 1) //Paper
        {
          System.out.println("Player Win");
        } else if (compChoice == 2) //Scissors
        {
          System.out.println("Computer Win");
        } else if (compChoice == 3) //Lizard
        {
          System.out.println("Tie, try again.");
        } else if (compChoice == 4) //Spock
        {
          System.out.println("Player Win");
        }
        break;


      case 4: //User chooses spock
        if (compChoice == 0) //Rock
        {
          System.out.println("Player Win");
        } else if (compChoice == 1) //Paper
        {
          System.out.println("Computer Win");
        } else if (compChoice == 2) //Scissors
        {
          System.out.println("Player Win");
        } else if (compChoice == 3) //Lizard
        {
          System.out.println("Computer Win");
        } else if (compChoice == 4) //Spock
        {
          System.out.println("Tie, try again.");
        }
        break;


      default:
        System.out.println("There was an error. Please try again.");
        break;
    }
  }
}

最初我认为我可以根据所选择的选项将字符串设置为一个值。看来我不能，而且我不确定它希望我如何将开关设置为 int。我认为我可能能够做的是，在我最初的 if 语句中，我没有将字符串设置为等于一个值，而是根据用户在 joption 部分中的选择将其设置为一个值。任何帮助或建议将不胜感激。

4

2 回答 2

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Java 是一种强类型的编程语言，这意味着你不能int仅仅因为你想就隐式地转换任何东西。您必须适当地转换它，无论是通过(int)userChoice或类似new Integer(userChoice)或什至userChoice.toInt()（如果提供）。因此...

switch((int)userChoice) { // Or whatever is the correct way for your objects to be converted to integers

...

}

有望解决您的问题。无论如何，您没有向我们提供足够的信息来找出对给定对象进行转换的正确和简洁的方法。

于 2015-10-08T23:04:44.547 回答
-1

首先，您不能Object在 switch 语句中使用 an。正如它告诉你的那样，你需要一个int. 在这里给出这些不同的值（像这样，并使用小写）：

final int rock = 0;
final int paper = 1;
final int scissors = 2;
final int lizard = 3;
final int spock = 4;

因此，创建另一个名为类似的变量userChoiceNumber，并更改此位（看起来像这样，我还建议将用户输入转换为小写，因为这是一个赋值，我会让你弄清楚）：

int userChoiceNumber = -1; // As a default value that you can check, or change to 0 for a valid default
if (userChoice.equals("Rock")) { // Instead of using == use equals
  userChoiceNumber = rock;
} else if (userChoice.equals("Paper")) {
  userChoiceNumber = paper;
} else if (userChoice.equals("Scissors")) {
  userChoiceNumber = scissors;
} else if (userChoice.equals("Lizard")) {
  userChoiceNumber = lizard;
} else if (userChoice.equals("Spock")) {
  userChoiceNumber = spock;
}

然后对于您的switch声明，您可以切换到 using userChoiceNumber，并且可以将 0-4 替换为final ints：

//Determine who wins
switch (userChoiceNumber) {
  case rock: //User chooses Rock

编辑：从使用更改为使用==正确.equals()处理字符串比较。

于 2015-10-08T22:56:54.483 回答