线程"main“java.util.scanner异常

Question

What is the result?
10 - 7 =
3
Congratulations, you got it correct!
Exception in thread "main" What is the result?
9 + 8 =
java.util.NoSuchElementException
at java.util.Scanner.throwFor(Unknown Source)
at java.util.Scanner.next(Unknown Source)
at java.util.Scanner.nextInt(Unknown Source)
at java.util.Scanner.nextInt(Unknown Source)
at proj3.Project4App.main(Project4App.java:28)

当我运行我的代码时，我得到了我的扫描器要通过的第一个循环，但后来我遇到了一个错误。我不确定我做错了什么？我需要让循环进行，直到10个问题被正确回答，20个问题被整体回答，或者正确答案的平均值超过85%。

package proj3;
import java.util.Scanner;
import java.util.Random;

/**
 * <p> Title: Project 4: The Project4App Class </p>
 * <p> Description: Creates an math game for children </p>
 * @author Justin Abeles
 */

public class Project4App {
    /**
     * <p> Name: main method </p>
     * 
     * @param args values to be sent to the method
     */
public static void main(String args[]){

    int addCorrect = 0;
    int addWrong = 0;
    int subCorrect = 0;
    int subWrong = 0;

    while(true){
        Question quiz = new Question();
        Scanner scan = new Scanner(System.in);
        System.out.println("What is the result?\n" + quiz.toString());
        int age = scan.nextInt();
        int answer = quiz.determineAnswer();
        char operator = quiz.getOperator();
        if(age == answer && operator == '+')
            System.out.println("Congratulations, you got it correct!");
        if((age == answer) && (operator == '-'))
            System.out.println("Congratulations, you got it correct!");
        if((age != answer) && (operator == '+'))
            System.out.println("The correct answer for " + quiz.toString() + " is " + quiz.determineAnswer());
        if((age != answer) && (operator == '-'))
            System.out.println("The correct answer for " + quiz.toString() + " is " + quiz.determineAnswer());


        if(age == answer && operator == '+')
            addCorrect = addCorrect + 1;
        else if(age == answer && operator == '-')
            subCorrect = subCorrect + 1;
        else if(age != answer && operator == '+')
            addWrong = addWrong + 1;
        else
            subWrong = subWrong + 1;
        scan.close();
    }
}

}

Answer 1

把Scanner scan = new Scanner(System.in);从你的生命周期中剔除。对scan.close;执行同样的操作，在退出main函数之前将其放入正确位置。当你close你的Scanner时，它也会关闭它的源代码。这可能是你例外的原因。