线程“main”java.util.NoSuChelementException中出现异常

Question

每当我运行这个函数时，chooseCave()函数与.nextint()中的都能很好地工作。当我选择洞穴时，消息以2秒的间隔弹出，然后当它超过这个部分时，它给了我错误：

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

我尝试了hasNextLine()和hasnextint()，当我在main方法中使用while hasNextLine()时，我会得到大量错误。当我在ChooseCave()方法中使用While hasNextInt()时，它不接受我的输入。

我已经看过了错误报告和类似问题的Java-docs和堆栈溢出。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();

}

}




Answer 1

您关闭了第二个扫描程序，它关闭了基础的InputStream，因此第一个扫描程序不能再读取相同的InputStream和NoSuchelementException结果。

解决方案：对于控制台应用程序，使用单个扫描器读取系统。在中。

旁白：如前所述，请注意scanner#nextint不使用换行符。通过使用scanner#newline()再次尝试调用nextline之前，请确保已使用这些代码。

请参见：不要在单个InputStream上创建多个缓冲包装