Java 为什么我输入的每个输入都会忽略我的 While 循环？答案

【问题标题】：Java Why is my While loop being ignored for every input I type in?Java 为什么我输入的每个输入都会忽略我的 While 循环？
【发布时间】：2020-02-16 13:57:44
【问题描述】：

我试图弄清楚为什么我的 main 方法中的 while 循环被忽略了，即使我没有输入“退出”。该程序应该接受用户的输入（转换为 int），让计算机生成一个随机 int（石头、纸或剪刀），比较两个 int，打印出答案，然后从头再来，直到“退出" 或任何其他无法识别的输入（不是石头、纸或剪刀）。

例如：UserInput = rock;输出：再见！！！（while 循环只是跳过，直接进入 if 循环，即使“userInput”（转换为 int 1）不等于“quit”（转换为 int 0）。试图修复它，如果UserInput =“rock”（转换为1），计算机随机生成“paper”（转换为2），输出将是“paper”获胜。

我已经尝试解决这个问题好几个小时了，感谢任何帮助，谢谢。

package rockPaperScissors;
import java.util.*

public class RockPaperScissors {
    public static final int quit = 0;
    public static final int rock = 1;
    public static final int paper = 2;
    public static final int scissors = 3;
    static Scanner console = new Scanner(System.in);

public static void main(String [] args) {
    //gets userHand from user as int
    int userHand = promptUserForHand();
    while(userHand != quit) {
        //gets computerHand from the computer(random) as int
        int computerHand = generateRandomHand();
        //compares userHand to computerHand, determines the winner
        String winner = determineWinner(userHand, computerHand);
        //prints out the winner
        System.out.println("The winner is the: " + winner);
        //starts the next round
        userHand = promptUserForHand();
    }
    //if userHand equals quit, stop program and say goodbye
    if(userHand == quit) {
        System.out.println("Goodbye!!!");
        console.close();        
    }
}

public static int promptUserForHand() {
    //gets userInput from user
    System.out.println("Please input either rock, paper, scissors (or enter quit to stop)");
    String userInput = console.next(); 
    //converts String into int, so userHand and computerHand can be compared
    int userHand = 0;
    if(userInput == "rock" || userInput == "Rock" || userInput == "r") {
        userHand  = rock;
    }
    else if(userInput == "paper" || userInput == "Paper" || userInput == "p") {
        userHand = paper;
    }
    else if(userInput == "scissors" || userInput == "Scissors" || userInput == "s"){
        userHand = scissors;
    }
    else {
        userHand = quit;
    }
    return userHand;
}

//generates computerHand from computer(randomly chooses either rock(1), paper(2), or scissors(3))
public static int generateRandomHand() {
    Random r = new Random();
    int computerHand = r.nextInt(4) + 1;
    return computerHand;
}

//compares userHand to computerHand to determine the winner
public static String determineWinner(int userHand, int computerHand) {
    String winner = " ";
    if(userHand == 1 && computerHand == 2) {
        winner = "Computer!!!";
    }
    else if(userHand == 1 && computerHand == 3) {
        winner = "User!!!";
    }
    else if(userHand == 2 && computerHand == 1) {
        winner = "User!!!";
    }
    else if(userHand == 2 && computerHand == 3) {
        winner = "Computer!!!";
    }
    else if(userHand == 3 && computerHand == 1) {
        winner = "Computer!!!";
    }
    else if(userHand == 3 && computerHand == 2) {
        winner = "User!!!";
    }
    else {
        winner = "Tie!!!";
    }       
    return winner;
}

}

【问题讨论】：

标签： java while-loop

【解决方案1】：

你不应该在java中使用==比较字符串。而是使用：equals() 或 equalsIgnoreCase() 方法。

例如：

代替：

 if(userInput == "rock" || userInput == "Rock" || userInput == "r")

使用：

if(userInput.equalsIgnoreCase("rock") || userInput.equalsIgnoreCase("r"))

为什么：检查这个答案：Why would you use String.Equals over ==?

【讨论】：