问题
I've searched up and down for the fix to my issue, but none seem to work. One particular reference-- this and this, and especially this. However, no matter how I implement them, I receive an OutOfBoundsError, which I can't understand.
The program is extra credit for a class. In truth, it is very simple--
Program Description: Use a two dimensional array to solve the following problem. A company has four sales persons (1 to 4) who sell five different products (1 to 5). Once a day, each salesperson passes in a slip for each different type of product sold. Each slip contains:
The sales persons number
The product number
The total dollar value of that product sold that dayThus, each salesperson passes in between 0 and 5 sales slips per day. Assume that the information from all of the slips for last month is available. Each data line contains 3 numbers (the sales person number, product number, sales).
Write a program that will read all this information for last month’s sales, and summarize the total sales by salesperson by product.
The data provided:
1 2 121.77
1 4 253.66
1 5 184.22
1 1 97.55
2 1 152.44
2 2 104.53
2 4 189.97
2 5 247.88
3 5 235.87
3 4 301.33
3 3 122.15
3 2 301.00
3 1 97.55
4 1 125.66
4 2 315.88
4 4 200.10
4 3 231.45
The error only comes when it tries to calculate the columns. My rows work; no matter how I change the for-loop or any of the indeces in the row or column of the array, it doesn't work. I at first had my rows calculated separately, then my column sums, and it didn't work either. There is something that I'm missing that I'm clearly overlooking.
Here is my code:
import java.io.File;
import java.io.FileNotFoundException;
import java.text.DecimalFormat;
import java.util.Scanner;
public class prog480u {
static Scanner inFile = null;
public static void main(String[] args) {
try {
// create scanner to read file
inFile = new Scanner(new File ("prog480u.dat"));
} catch (FileNotFoundException e) {
System.out.println("File not found!");
System.exit(0);
}
// make the array
int x = 0;
int y = 0;
double[][] profits = new double[4][5];
while (inFile.hasNext()) {
x = inFile.nextInt(); // use sales numbers as coordinates
y = inFile.nextInt();
profits[x - 1][y - 1] = inFile.nextDouble();
}
// check if it's okay
System.out.println("");
double[][] columnProfits = sums(profits);
for (int a = 0; a < columnProfits.length; a++) {
System.out.print((a+1) + "\t");
for (int b = 0; b < columnProfits[a].length; b++) {
System.out.print(columnProfits[a][b] + "\t");
}
System.out.println("");
}
double[] bottomRow = columnSums(columnProfits);
for (int a = 0; a < bottomRow.length; a++) {
System.out.print("Total:" + bottomRow + "\t");
}
}
public static double[][] sums (double[][] q) {
double[][] array = new double[5][6];
array = q;
double sum = 0;
for (int a = 0; a < array.length; a++) {
for (int b = 0; b < array[0].length; b ++) {
sum += array[a][b]; // add everything in the row
}
array[a][4] = sum; // set that row to the last column
sum = 0; // reset sum to 0
}
return array;
}
public static double[] columnSums (double[][]q) {
double[][] array = new double[5][6];
array = q;
double sum2 = 0;
double[] columns = new double [5];
for (int a = 0; a < array.length; a++) {
for (int b = 0; b < array[0].length; b ++) {
sum2 += array[b][a];
columns[b] = sum2;
}
sum2 = 0; // reset sum to 0
}
return columns;
}
}
Thank you very much for your time. I have a feeling my program is close to working, but this small mistake is pushing me over the edge.
回答1:
Here's the working code (I cleaned it up a bit):
You were very close, you just needed to swap your max indicies in the for loops. That's why you were getting a java.lang.ArrayIndexOutOfBoundsException
public static double[] columnSums(double[][] q)
{
double[][] array = q;
double[] columns = new double[5];
for (int a = 0; a < array[0].length; a++)
{
for (int b = 0; b < array.length; b++)
{
columns[a] += array[b][a];
}
}
return columns;
}
回答2:
Just for fun, I wrote the object oriented version for that. Easier to handle once the system requires additional functionalities:
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map.Entry;
class Sale {
static public ArrayList<Sale> readSales(final String pSalesFileName) throws FileNotFoundException, IOException {
final ArrayList<Sale> ret = new ArrayList<>();
try (final BufferedReader br = new BufferedReader(new FileReader(pSalesFileName))) {
int lineIndex = 0;
while (true) {
++lineIndex;
final String line = br.readLine();
if (line == null) {
System.out.println("Line #" + lineIndex + " is empty, skipping...");
break;
}
try {
final String[] values = line.split("\\s");
final int salesPersonId = Integer.parseInt(values[0]);
final int productId = Integer.parseInt(values[1]);
final float sales = Float.parseFloat(values[2]);
final Sale sale = new Sale(salesPersonId, productId, sales);
ret.add(sale);
} catch (final ArrayIndexOutOfBoundsException e) {
System.err.println("Parse error in line #" + lineIndex + ": '" + line + "'");
}
}
}
return ret;
}
private final int mSalesPersonId;
private final int mProductId;
private final float mSales;
public Sale(final int pSalesPersonId, final int pProductId, final float pSales) {
mSalesPersonId = pSalesPersonId;
mProductId = pProductId;
mSales = pSales;
}
public Integer getSalesPersonId_R() {
return Integer.valueOf(mSalesPersonId);
}
public Integer getProductId_R() {
return Integer.valueOf(mProductId);
}
public float getSales() {
return mSales;
}
}
class SalesPerson {
private final HashMap<Integer, ArrayList<Sale>> mSalesMap = new HashMap<>();
private final int mId;
public SalesPerson(final int pId) {
mId = pId;
}
@Override public boolean equals(final Object pObj) {
if (!(pObj instanceof SalesPerson)) return false;
return ((SalesPerson) pObj).mId == mId;
}
@Override public int hashCode() {
return mId;
}
public void addSale(final Sale pSale) {
final Integer productId = pSale.getProductId_R();
ArrayList<Sale> salesList = mSalesMap.get(productId);
if (salesList == null) {
salesList = new ArrayList<>();
mSalesMap.put(productId, salesList);
}
salesList.add(pSale);
}
public Integer getId_R() {
return Integer.valueOf(mId);
}
public HashMap<Integer, ArrayList<Sale>> getSalesMap() {
return mSalesMap;
}
public float getSalesTotalByProductId(final Integer pProductId) {
final ArrayList<Sale> sales = mSalesMap.get(pProductId);
float accumulator = 0;
for (final Sale sale : sales) {
accumulator += sale.getSales();
}
return accumulator;
}
}
public class SalesFun {
public static void main(final String[] args) throws FileNotFoundException, IOException {
final ArrayList<Sale> sales = Sale.readSales("test/sales.txt");
final HashMap<Integer, SalesPerson> personMap = new HashMap<>();
for (final Sale sale : sales) {
// find right salesperson or create new, then add sale to it
final Integer salesPersonId = sale.getSalesPersonId_R();
SalesPerson person = personMap.get(salesPersonId);
if (person == null) {
person = new SalesPerson(salesPersonId.intValue());
personMap.put(salesPersonId, person);
}
person.addSale(sale);
}
printSales(personMap);
}
static private void printSales(final HashMap<Integer, SalesPerson> pPersonMap) {
for (final SalesPerson person : pPersonMap.values()) {
System.out.println("SalesMan ID: " + person.getId_R());
for (final Entry<Integer, ArrayList<Sale>> entry : person.getSalesMap().entrySet()) {
final Integer productId = entry.getKey();
final float sales = person.getSalesTotalByProductId(productId);
System.out.println("\tProduct ID: " + entry.getKey() + "\tSales: " + sales);
}
}
}
}
来源：https://stackoverflow.com/questions/36877667/sum-of-columns-and-rows-of-2d-array