为什么我的JAVA代码中出现此错误？

Question

生日悖论说，一个房间中的两个人有相同的生日的概率是该房间中的人数（n）的一半以上，即大于23。此属性并不是真正的悖论，而是许多人发现这令人惊讶。 设计一个C ++程序，该程序可以通过在随机生成的生日上进行一系列实验来测试该悖论，该实验针对n = 5、10、15、20，...测试该悖论。 。 。 ，即100。您应该为n的每个值至少运行10个实验，并且应该为每个n输出该n的实验数量，以使该测试中的两个人有相同的生日。

package birth;
import java.util.Random;

/* Question: 
The birthday paradox says that the probability that two people in a room
will have the same birthday is more than half as long as the number of
people in the room (n), is more than 23. This property is not really a paradox,
but many people find it surprising. Design a C++ program that can
test this paradox by a series of experiments on randomly generated birthdays,
which test this paradox for n =5, 10, 15, 20, . . . , 100. You should run
at least 10 experiments for each value of n and it should output, for each
n, the number of experiments for that n, such that two people in that test
have the same birthday.
*/

public class birth {

public static final int YEAR = 365;

public static void main(String[] args)
{

    int numOfPeople = 5;
    int people = 5;

    //DOB array
    int[] birthday = new int[YEAR];



    //Creates an array that represents 365 days
    for (int i = 0; i < birthday.length; i++)
        birthday[i] = i + 1;

    //Random Number generator
    Random randNum = new Random();

    int iteration = 1;

    //iterates around peopleBirthday array
    while (numOfPeople <= 100)
    {
        System.out.println("Iteration: " + iteration);
        System.out.println();
        //Creates array to holds peoples birthday
        int[] peopleBirthday = new int[numOfPeople];


        //Assigns people DOB to people in the room
        for (int i = 0; i < peopleBirthday.length; i++)
        {
            int day = randNum.nextInt(YEAR + 1);
            peopleBirthday[i] = birthday[day];


        }
        for (int i = 0; i < peopleBirthday.length; i++)
        {   


            //stores value for element before and after
            int person1 = peopleBirthday[i];
            int person2 = i + 1;

            //Checks if people have same birthday
            for (int j = person2; j < peopleBirthday.length; j++)
            {


                //Prints matching Birthday days
                if (person1 == peopleBirthday[j])
                {
                    System.out.println("P1: " + person1 + " P2: " + peopleBirthday[j]);
                    System.out.println("Match!!! \n");

                }
            }
        }


        //Increments the number of people in the room
        numOfPeople += 5;
        iteration++;
    }

    }
}

我收到一个错误： java.lang.ArrayIndexOutOfBoundsException: 365我无法弄清楚我的代码出了什么问题

Answer 1

如果您提供了引发异常的确切行号（信息在您得到的错误堆栈跟踪中），那将是很好的选择，但是很有可能在这里发生问题：

int day = randNum.nextInt(YEAR + 1); // 365 + 1 = 366
peopleBirthday[i] = birthday[day];

Random.nextInt的文档说：

返回：下一个伪随机数，此随机数生成器的序列在0（含）和有界（不含）之间均匀分布的int值。

在这种情况下，您将调用366 （ 365 + 1 ）值的Random.nextInt ，这意味着您正在有效地读取0到365之间的某个随机数。 如果您确实得到365 ，则将使birthday[day]超出范围，因为数组的最大索引为364而不是365 。

您可能打算用这种方式读取随机值：

int day = randNum.nextInt(YEAR); // 365 (exclusive)

Answer 2

Java中的数组从零开始。 如果您创建的birthday长度为365 ，则索引的范围为0到364 。

您需要从以下更改此行：

int[] birthday = new int[YEAR];

对此：

int[] birthday = new int[YEAR+1];