每次循环继续时，创建的2d数组会覆盖先前创建的2d数组，如何创建单独的2d数组并按下面列出的方式访问/更改它。
我目前是一名高中学生，参加在线计算机科学课程，并希望通过编码提高我的效率，并获得一些关于我的坏习惯的提示。这是我的计划：
import java.util.Arrays;
import java.util.Scanner;
public class FundRaising
{
public static void main(String[] args)
{
Scanner scanner = new Scanner(System.in);
System.out.println("Would you like to input donation information regarding the selected schools?\n0 - Yes\n1 - No"); //runs the program or ends the program
Integer loop = scanner.nextInt();
while (loop == 0) //while the user would like to run the program, the code will look
{
if (loop == 0) //continues if the user would like to continue
{
System.out.println("Which school is fundraising?\n0 - Central\n1 - Holy Cross\n2 - John Paul II\n3 - Teresa\n4 - Regina\n5 - Joeseph\n6 - Mary\n7 - Thomas Aquinas");
Integer school = scanner.nextInt(); //asks which school information will be input for
System.out.println("Amount donated?\n0 - 25 cents\n1 - 50 cents\n2 - 1 dollar\n3 - 2 dollars");
Integer donation = scanner.nextInt(); //asks the amount donated
System.out.println("School population?");
Integer population = scanner.nextInt(); //asks the population of the school
if (donation == 0) //if the first donation amount is selected then this selection will be used
{
double schoolTotal = 0.25*population; //the donation amount times the population gives the total for the school selected
System.out.println(" Cen Cross Paul Trsa Rgna Joes Mary Tom Amnt Total"); //prints out headers for the 2d array
int rows = 4; //set the initial size of the 2d array according to schools and donations
int columns = 10;
double totals [][] = new double [rows][columns]; //initialize the 2d array
totals[0][8] = 0.25;
totals[1][8] = 0.5; //set various positions on the 2d array to equal the donation amounts
totals[2][8] = 1.00;
totals[3][8] = 2.00;
totals[donation][school] = schoolTotal; //set the positions corredsponding to the input school and donation in order to create a "total" column on the 2d array
totals[donation][9] = totals[0][0]+totals[0][1]+totals[0][2]+totals[0][3]+totals[0][4]+totals[0][5]+totals[0][6]+totals[0][7]; //the sums of everything in the row is used to find a value for the total column
double finalDonations = totals[0][9]+totals[1][9]+totals[2][9]+totals[3][9]; //adds the total for each school in the total column to create a final total for donations
System.out.print(Arrays.deepToString(totals).replace("], ", "]\n ")); //prints out the 2d array with slight modifications for easier viewing
System.out.println("\nTotals donations:" + finalDonations +""); //prints the total amount of donations to the user
}
if (donation == 1) //each subsequence if statement is used if the donation amount differs (4 different donations amounts, 25 cents, 50 cents, 1 dollar and 2 dollars
{ //remainder of code is drycut paste with small modifications to adjust for differing donation amount
double schoolTotal = 0.50*population;
System.out.println(" Cen Cross Paul Trsa Rgna Joes Mary Tom Amnt Total");
int rows = 4;
int columns = 10;
double totals [][] = new double [rows][columns];
totals[0][8] = 0.25;
totals[1][8] = 0.5;
totals[2][8] = 1.00;
totals[3][8] = 2.00;
totals[donation][school] = schoolTotal;
totals[donation][9] = totals[1][0]+totals[1][1]+totals[1][2]+totals[1][3]+totals[1][4]+totals[1][5]+totals[1][6]+totals[1][7];
double finalDonations = totals[0][9]+totals[1][9]+totals[2][9]+totals[3][9];
System.out.print(Arrays.deepToString(totals).replace("], ", "]\n "));
System.out.println("\nTotals donations:" + finalDonations +"");
}
if (donation == 2)
{
double schoolTotal = 1.00*population;
System.out.println(" Cen Cross Paul Trsa Rgna Joes Mary Tom Amnt Total");
int rows = 4;
int columns = 10;
double totals [][] = new double [rows][columns];
totals[0][8] = 0.25;
totals[1][8] = 0.5;
totals[2][8] = 1.00;
totals[3][8] = 2.00;
totals[donation][school] = schoolTotal;
totals[donation][9] = totals[2][0]+totals[2][1]+totals[2][2]+totals[2][3]+totals[2][4]+totals[2][5]+totals[2][6]+totals[2][7];
double finalDonations = totals[0][9]+totals[1][9]+totals[2][9]+totals[3][9];
System.out.print(Arrays.deepToString(totals).replace("], ", "]\n "));
System.out.println("\nTotals donations:" + finalDonations +"");
}
if (donation == 3)
{
double schoolTotal = 2.00*population;
System.out.println(" Cen Cross Paul Trsa Rgna Joes Mary Tom Amnt Total");
int rows = 4;
int columns = 10;
double totals [][] = new double [rows][columns];
totals[0][8] = 0.25;
totals[1][8] = 0.5;
totals[2][8] = 1.00;
totals[3][8] = 2.00;
totals[donation][school] = schoolTotal;
totals[donation][9] = totals[3][0]+totals[3][1]+totals[3][2]+totals[3][3]+totals[3][4]+totals[3][5]+totals[3][6]+totals[3][7];
double finalDonations = totals[0][9]+totals[1][9]+totals[2][9]+totals[3][9];
System.out.print(Arrays.deepToString(totals).replace("], ", "]\n "));
System.out.println("\nTotals donations:" + finalDonations +"");
}
}
else //if the user did not chose to run the program this message is displayed
{
System.out.println("You did not not choose to input information");
}
}
}
}
答案 0 :(得分：1)
实际上，每次循环迭代都会创建新数组。
移动这部分
int rows = 4; //set the initial size of the 2d array according to schools and donations
int columns = 10;
double totals [][] = new double [rows][columns]; //initialize the 2d array
到主方法，就在Scanner scanner = new Scanner(System.in);之后，并从循环内部删除它，所以下次学校的捐赠值不会被覆盖。
然后，如果你想要捐款增加的总和，你应该改变
totals[donation][school] = schoolTotal;到
totals[donation][school] = totals[donation][school] + schoolTotal;
或者保持原样。
答案 1 :(得分：0)
我真的不明白你的问题是什么，但我建议你开始使用for循环而不是代码重复。
这样的行：
totals[donation][9] = totals[0][0]+totals[0][1]+totals[0][2]+totals[0][3]+totals[0][4]+totals[0][5]+totals[0][6]+totals[0][7];
应替换为：
for(int i=0; i<8; i++) (or i<totals[0].length if you want to run on all the cells)
totals[donation][9]+=totals[0][i];
答案 2 :(得分：0)
考虑使用Collections代替数组来操作这样的数据。例如。 Map<String, Integer>用于处理不同的捐赠来源和价值