我目前正在通过教科书教我自己一些基本的Java并给自己一个“作业问题”，但是在写一个方法的.txt文件时我遇到了困难。它不想超过2人。以下是该方法的简要说明：
1。）收集用户想要输入数据文件的人数
2。）以二维数组收集每个人的名字和姓氏
3。）收集用户为用户输入数组的每个（单独）人设置的一些付款。
4.）然后它计算进入另一个阵列的每个人的平均付款（因此每个人应该有自己的平均值）
5.）最后，它将数据写入名为“BusinessData.txt。”的.txt文件中。
在尝试将超过2个人写入.txt文件之前，似乎工作正常。它让我疯狂，我真的想知道如何解决这个问题，然后继续讨论下几个主题。
以下是我尝试添加超过2个人时收到的错误消息：
线程“main”中的异常java.lang.Array IndexOutofBoundsException： 3
在Business1.dataCollect（Business1.java:210）
在Business1.main（Business1.java:62）
我非常感谢任何提示。
这是实际的代码：
import java.util.*;
import java.io.*;
public class Business1
{
public static void main(String[] args) throws IOException
{
// Declare local variables
int menuChoice;
// Declare local objects
Scanner input = new Scanner(System.in);
// Display the program title
System.out.println("\n\n\n\n\t\t\t\t***************************************\n"
+ "\t\t\t\t* Average Customer Payment Calculator *\n"
+ "\t\t\t\t***************************************\n\n\n");
// Start of a do-while loop: Continues the program as long as the user doesn't choose to exit
do
{
// Start of a do-while loop: Input Validation (menuChoice must be between 1 - 4)
do
{
// Prompt user for menuChoice
System.out.print("\tPlease enter an integer in accordance to the given choices:\n\n"
+ "\t(1) Collect and Erase Old Data\n"
+ "\t(2) Read Saved Data\n"
+ "\t(3) Append Old Data\n"
+ "\t(4) Exit Program\n\n"
+"\tEnter Choice: ");
menuChoice = input.nextInt();
System.out.println("\n\n");
// If menuChoice is equal to 1: Erase old Data and Collect and Write new data
if(menuChoice == 1)
{
try
{
dataCollect();
}
catch(IOException e)
{
System.out.println("Error");
}
}
// else if menuChoice is equal to 2: Read Saved Data
else if(menuChoice == 2)
{
}
// else if menuChoice is equal to 3: Append Old Data
else if(menuChoice == 3)
{
}
// else if menuChoice is equal to 4: Exit Program
else if(menuChoice == 4)
{
System.out.println("\n\n\n\t\tGoodbye!\n\n\n");
}
// else display error message: Error. Please enter a number 1 - 4
else
{
System.out.println("\n\nERROR. Please enter a number 1 - 4\n\n");
}
// End of do-while loop: Input Validation (menuChoice must be between 1 - 4)
} while(menuChoice < 1 || menuChoice > 4);
// End of a do-while loop: Continues the program as long as the user doesn't choose to exit
} while(menuChoice != 4);
}
// Create a method named dataCollect
public static void dataCollect() throws IOException
{
// Declare local variables
int numPeople, numPayments /* array size for payments */;
double totalPayments = 0, averagePayment;
double [] paymentsArray /* different payments */, averagePaymentsArray;
String [][] namesArray /* First name, last name in array */;
// Declare objects
Scanner keyboard = new Scanner(System.in);
// Prompt user for the number of people they would like to add to the records and store in variable numPeople
System.out.print("\tHow many people would you like to add to your records?\n\n\tEnter an integer: ");
numPeople = keyboard.nextInt();
System.out.println("\n\n");
// Initialize arrays
namesArray = new String[numPeople][2];
// Create a counter for the for-loop
int count = 0;
// For-loop will prompt user for first and last name of each person
for(int i = 1; i <= numPeople; i++)
{
// Consume the remaining newline character
keyboard.nextLine();
// Prompt user for first name
System.out.print("\tPlease enter the FIRST name of person #" + i +": ");
namesArray[count][0] = keyboard.nextLine();
System.out.println("\n\n");
//Prompt user for last name
System.out.print("\tPlease enter the LAST name of person #" + i + ": ");
namesArray[count][1] = keyboard.nextLine();
System.out.println("\n\n\n");
count++;
}
// Reset counter for the next for-loop
count = 0;
int count2 = 1; // Used to keep track of which payment number the user is inputing
int count3 = 0;
int count4 = -1;
// ****************************************************************
// * Open file for input ******************************************
// ****************************************************************
PrintWriter outputFile = new PrintWriter("BusinessData.txt");
outputFile.println("\t\t\tBusiness Data\n\n");
outputFile.println("First Name\tLast Name\tP 1\t\tP 2\t\t P 3\t\tAverage Payments\n\n"
+ "------------------------------------------------------------------------------------------------------------------------------------------------------\n");
// For-loop will ask for number of payments each person made while also collecting the value of each of those payments in a nested for-loop.
for(int i = 0; i < numPeople; i++)
{
// Prompt user for first name
System.out.print("\tPlease enter the number of payments made by " + namesArray[count][0] +" " + namesArray[count][1] + "(Put in 3 for now) : ");
numPayments = keyboard.nextInt();
System.out.println("\n\n");
// Initialize array then reset it for the next person to come
paymentsArray = new double[numPayments];
for(int j = 0; j < numPayments; j++)
{
// ****************************************************************
// * Open file for input ******************************************
// ****************************************************************
System.out.print("\n\n\tPlease enter payment value of payment #" + count2 + " that " + namesArray[count][0] +" " + namesArray[count][1] + " made: $");
paymentsArray[j] = keyboard.nextDouble();
System.out.println("\n\n");
// Increment counter
count2++;
}
// ************************************************************************
// * Calculating Average Payment ******************************************
// ************************************************************************
// For loop for calculating average
for(int k = 0; k < numPayments; k++)
{
totalPayments += paymentsArray[k];
}
// Calculate the Average Payment
averagePayment = totalPayments/paymentsArray.length;
/**************************************************
********** BUG LIES IN THE WRITING **************
***************************************************/
// nested for-loop will write data now otherwise it'll just be wiped out and overwritten by the next input
for(int l = 1; l < numPeople; l++)
{
// Increment counter4
count4++;
// Output first name
outputFile.print(namesArray[count4][count3]);
// Increment counter3
count3++;
// Output last name
outputFile.print("\t\t" + namesArray[count4][count3] + "\t\t");
// Reset counter3
count3 = 0;
for (int m = 0; m < numPayments; m++)
{
outputFile.print(paymentsArray[m] + "\t\t");
}
outputFile.println(averagePayment + "\n\n");
}
// Reset total Payments for the next iteration
totalPayments = 0.0;
// Increment the counter
count++;
}
outputFile.close();
// End of dataCollect method
}
答案 0 :(得分：0)
运行代码会为3个以上的用户提供异常。 抛出
的ArrayIndexOutOfBoundsException outputFile.print(namesArray[count4][count3]);
在调试模式下运行表明namesArray [count4] [count3]指向一个不可用的值。
由于以下循环，count4增加到超出界限值。
我不知道为什么你需要这个循环
for(int l = 1; l < numPeople; l++)
{
enter code here}
如果删除它，它可以正常工作。