每当我运行它时，chooseCave() 函数与 in.nextInt() 一起正常工作。当我选择洞穴时，消息以 2 秒的间隔弹出，然后一旦它通过该部分，它就会给我错误:

Exception in thread "main" java.util.NoSuchElementException: No line found
    at java.util.Scanner.nextLine(Unknown Source)
    at Dragon.main(Dragon.java:81)

我已经尝试过 hasNextLine() 和 hasNextInt()，当我在 main< 中使用="">while hasNextLine() 时 方法，我得到了更多的错误。当我在 chooseCave() 方法中使用 while hasNextInt() 时，它不接受我的输入。

当我在 chooseCave() 方法中使用 if hasNextInt() 时，它不接受我对 playAgain 字符串的输入，并直接进入另一个游戏，但随后 hasNextInt() boolean 值返回 false 并且它无限地发送垃圾邮件“Which cave...”。

我已经浏览了错误报告和 Java 文档以及 Stack Overflow 的类似问题。请帮忙。

import java.util.Scanner;
public class Dragon {

public static void displayIntro() {
    System.out.println("You are in a land full of dragons. In front of you, ");
    System.out.println("You see two caves. In one cave, the dragon is friendly");
    System.out.println("and will share his treasure with you. The other dragon");
    System.out.println("is greedy and hungry, and will eat you on sight");
    System.out.println(' ');
}

public static int chooseCave() {
    Scanner in = new Scanner(System.in);
    int cave = 0;
    while (cave != 1 && cave != 2) {
        System.out.println("Which cave will you go into? (1 or 2)");

        cave = in.nextInt();

    }
    in.close();
    return cave;
} 

public static void checkCave(int chosenCave) {
    System.out.println("You approach the cave...");
    try
       {
       // Sleep at least n milliseconds.
       // 1 millisecond = 1/1000 of a second.
       Thread.sleep( 2000 );
       }
    catch ( InterruptedException e )
       {
       System.out.println( "awakened prematurely" );
       }
    System.out.println("It is dark and spooky...");
    try
       {
       // Sleep at least n milliseconds.
       // 1 millisecond = 1/1000 of a second.
       Thread.sleep( 2000 );
       }
    catch ( InterruptedException e )
       {
       System.out.println( "awakened prematurely" );
       }
    System.out.println("A large dragon jumps out in front of you! He opens his jaws and...");
    try
       {
       // Sleep at least n milliseconds.
       // 1 millisecond = 1/1000 of a second.
       Thread.sleep( 2000 );
       }
    catch ( InterruptedException e )
       {
       System.out.println( "awakened prematurely" );
       }

    double friendlyCave = Math.ceil(Math.random() * 2);

    if (chosenCave == friendlyCave) {
        System.out.println("Gives you his treasure!");
    }
    else {
        System.out.println("Gobbles you down in one bite!");
    }



}
public static void main(String[] args) {
    Scanner inner = new Scanner(System.in);
    String playAgain = "yes";
    boolean play = true;
    while (play) {
        displayIntro();
        int caveNumber = chooseCave();
        checkCave(caveNumber);
        System.out.println("Do you want to play again? (yes or no)");
        playAgain = inner.nextLine();
        if (playAgain == "yes") {
            play = true;
        }
        else {
            play = false;
        }
    }
    inner.close();

}

}

最佳答案

您关闭了第二个 Scanner，它关闭了底层 InputStream，因此第一个 Scanner 无法再从同一个 InputStream 中读取 和 NoSuchElementException 结果。

解决方案:对于控制台应用程序，使用单个 Scanner 从 System.in 中读取。

旁白:如前所述，请注意 Scanner#nextInt 不使用换行符。确保在尝试使用 Scanner#newLine() 再次调用 nextLine 之前消耗这些内容。

参见:Do not create multiple buffered wrappers on a single InputStream

关于java - 线程 "main"java.util.NoSuchElementException 中的异常，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/15398703/