title: Reading XLS file using Apache POI into 2D array in Java
body: <p>My assignment is to read an Excel file which looks like this
  <a href="http://postimg.org/image/jxgc6ng51/" rel="nofollow">http://postimg.org/image/jxgc6ng51/</a>
  and then sum the units of matching product ID and print them out in similar column/row format. Sorry if this is a sloppy way of doing it, I'm new to java and my knowledge of java API is very limited currently... Here is my code:</p>
  
  <pre><code>import java.io.FileInputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.util.*;
  
  import org.apache.poi.hssf.usermodel.HSSFCell;
  import org.apache.poi.hssf.usermodel.HSSFRow;
  import org.apache.poi.hssf.usermodel.HSSFSheet;
  import org.apache.poi.hssf.usermodel.HSSFWorkbook;
  
  public class Read {
  
              public static void readXLSFile() throws IOException{
          InputStream ExcelFile = new FileInputStream("C:/Sales Data.xls");
          HSSFWorkbook wb = new HSSFWorkbook(ExcelFile);
                  HSSFSheet sheet=wb.getSheetAt(0);
                  int numRows=sheet.getPhysicalNumberOfRows();
                  int[][]idSale=new int[numRows][2];
  
                  for(int i=1;i&lt;numRows;i++){
                      HSSFCell proId = sheet.getRow(i).getCell(1);
                      HSSFCell sales = sheet.getRow(i).getCell(2);
                      idSale[i][0]=(int)proId.getNumericCellValue();
                      idSale[i][1]=(int)sales.getNumericCellValue();
                      //the data from the excel sheet is copied into the 2D array at this point
                  }
  
                  /*for loop to attempt to compare id number of array to the rest of the array
                  problem is there are duplicate ID's and it is re-comparing and adding
                  the sales total into the duplicate as well. 
                  How to make it so it ignores all duplicate ID's or make it so it 
                  only prints out the element the first time the ID pops up and doesn't print the other elements with the same ID?*/
                  for(int j=1;j&lt;numRows;j++){
                      for(int jj=j+1;jj&lt;numRows;jj++)
                      if(idSale[j][0]==idSale[jj][0]){
                          idSale[j][1]+=idSale[jj][1];
                      }
                  }
              }
  
  
  
              public static void main(String[] args) throws IOException {
          readXLSFile();
              }
  }
  </code></pre>