java - 为什么这个数组初始值设定项会抛出 NullPointerException？

Question

我目前正在学习 Java，我想知道为什么这段代码会在下面指示的行处抛出 NullPointerException。 Question对象是一个用户定义的类，在初始化该对象时采用两个字符串作为参数。

public class QuizTime
{
    public static void main (String[] args)
    {
            Quiz qz = new Quiz();

            // Throws a NullPointerException
            qz.add (new Question ("How may US states are there?", "50"));
    }
}

下面是支持类。 NullPointerException 还表明“quiz[count] = q;”行存在问题

import java.util.Scanner;

public class Quiz
{   
    private Question[] quiz;
    private int count;
    private final int MAX_QUESTIONS = 25;

    public void Quiz ()
    {
            quiz = new Question[MAX_QUESTIONS];
            count = 0;
    }

    public void add (Question q)
    {
            if (count < MAX_QUESTIONS)
            {
                    // Throws a NullPointerException
                    quiz[count] = q;
                    count++;
            }
    }

Answer 1

public void Quiz ()

应该是

public Quiz() 

为了被视为构造函数并正确初始化您的对象。否则，它是您尚未调用的方法。