java - Equals 函数在 While 循环中不起作用

Question

我有代码应该猜测用户的号码，它会根据用户输入缩小搜索范围。唯一的问题是，在 while 循环中，条件语句不适用于 .equals。相反，即使我输入“小于”，它也会跳到其他。这是我的代码，我是java新手，所以我可能犯了一个错误。

package reversedHiLo;
//Import utility
import java.util.*;

public class ReversedHiLo 
{

public static void main(String[] args) 
    {
        //create scanner class
        Scanner sc = new Scanner(System.in);
        System.out.println("Welcome to reverse number guessing game, pick a number between 1 and 100 and type it below:");
        int answer = sc.nextInt();
        //Create the first guess
        int guess = 1 + (int)(100*Math.random());
        //Create an array that stores the range of the player's number
        int[] range = new int[] {1,100};
        //While loop that guesses the number
        while(guess != answer)
        {
            System.out.println("Is your number greater than or less than " + guess + "?" + Arrays.toString(range));
            String response = sc.next();
            sc.nextLine();
            //Conditionals to set the range of the guess
            if(response.equals("less than"))
            {
                range[1] = guess;
            }
            else
            {
                range[0] = guess;
            }
            //Guess a new number based on the range
            guess = range[0] + (int)((range[1] - range[0]) * Math.random());            
        }

        //Final print
        System.out.println("Your number was " + answer + ".\nThe computer's guess was: " + guess);
        //Close scanner
        sc.close();
    }

}

Answer 1

有两个地方有问题:

• 第一个 sc.nextInt() 方法 - 仅读取 int value by 将当前读取缓冲区保持在同一行。所以为了 忽略/跳过输入行中 int 之后的所有内容(即 可能是\n 或\r\n 如果你只输入数字)你必须 使用sc.nextLine()。
• 第二个是 sc.next() 方法 - 其中 只读取行中的第一个标记(或简单的单词)。那是 可能为什么你只得到分配给响应的“更少”值 并且永远不会.等于到“小于”。所以你会 必须将 sc.next() 替换为 sc.nextLine() 并删除 下一行中不必要的 sc.nextLine() 。

希望现在应该清楚了，并且您可以更好地理解调用这些函数时会发生什么。如果没有，那么我强烈建议您查看 Scanner 类，请阅读 JavaDocs围绕它编写多个测试，以更好地了解正在发生的事情。

如果我的解释仍然不清楚，请查看下面我为您修改的代码:

public static void main(String[] args)
{
    //create scanner class
    Scanner sc = new Scanner(System.in);
    System.out.println("Welcome to reverse number guessing game, pick a number between 1 and 100 and type it below:");
    int answer = sc.nextInt();
    sc.nextLine();   // This one is necessary to ignore everything on the same line as your number was typed in
    //Create the first guess
    int guess = 1 + (int)(100*Math.random());
    //Create an array that stores the range of the player's number
    int[] range = new int[] {1,100};
    //While loop that guesses the number
    while(guess != answer)
    {

        System.out.println("Is your number greater than or less than " + guess + "?" + Arrays.toString(range));
        String response = sc.nextLine();  // This reads the whole input line

        //Conditionals to set the range of the guess
        if(response.equals("less than"))
        {
            range[1] = guess;
        }
        else
        {
            range[0] = guess;
        }
        //Guess a new number based on the range
        guess = range[0] + (int)((range[1] - range[0]) * Math.random());
    }

    //Final print
    System.out.println("Your number was " + answer + ".\nThe computer's guess was: " + guess);
    //Close scanner
    sc.close();
}