Read data from excel file

Question

I have searched through StackOverflow, but didn't find a clear answer to my question.

I have a simple 2 columns and 24 rows xlsx (excel) file (later on this file will have more columns and rows , and also eventually it will have different sheets).

First row is header row: year=x and population=y, and for each header I want to read the rows below. Later on I want to be able to use this information to create a dynamic plot (x,y),

So I think I need to save the x and y information in variables. Below is my pseudo code.

//Sheet Pop

final String POP = "Pop";   
int startRowHeader = 1,      
    startRowNumeric = 2,     
    startColNumeric = 1, 
    nrOfCols = 0,
    nrOfRows  = 0;

int nrOfSheets = excelFile.getWorkbook().getNumberOfSheets(); 
org.apache.poi.ss.usermodel.Sheet sheet1 = excelFile.getWorkbook().getSheetAt(0);  
String[] sheets = {POP};
boolean sheetExists;
String activeSheet = "";   

nrOfCols = sheet1.getRow(0).getLastCellNum();
 nrOfRows = excelFile.getLastRowNum(POP);

try {

    for (String sheet : sheets) {
        sheetExists = false;
        for (int sheetIndex = 0; sheetIndex < nrOfSheets; sheetIndex++) {
        if (sheet.equalsIgnoreCase( excelFile.getWorkbook().getSheetName(sheetIndex))) { 
                SheetExists = true; 
            }
        }
        if (!sheetExists) {
            throw new Exception("Sheet " + sheet + " is missing!");
        }
    } 


    //Take off!

    // Sheet Pop
    activeSheet = sheets[0];

    for(int j=0; j < nrOfCols; j++) {
        for(int i=0; i<nrofRows; i++) {
            column[i] = (int)excelFile.getCellNumericValue(POP, startRowNumeric, startColNumeric);  
        }
    } 

}  catch (Exception e) {
    traceln(" ..... ");
    traceln("Error in sheet: " + activeSheet);
    traceln("Message: " + e.getMessage());  //Write out in console
} 

Answer 1

create a new class:

public class Point {
        int x;
        int y;

}

in your main function create a

List<Point> allPoints = new List<Point>();

then add the points you read from excel to this List

do this in a loop

Point p = new Point();
p.x = xCoordinateFromExcel;
p.y = yCoordinateFromExcel;

allPoints.add(p);

also consider adding constructor and getter/setters to your Point class.

also you might want to use the Point class available in java.awt directly. http://docs.oracle.com/javase/7/docs/api/java/awt/Point.html

EDIT: regarding fetching values from excel this is what i understand from your question you have 24 rows with 2 columns first column has x, second column has y value

so you can just do something like this in a loop

for(int i=0;i<24;i++){
    Row row = sheet.getRow(i);    
    Cell cellX = row.getCell(1);
    Cell cellY = row.getCell(2);

//assign to point class
...
}

dont forget to parse it to int, or use getNumericCellValue() http://poi.apache.org/apidocs/org/apache/poi/ss/usermodel/Cell.html#getNumericCellValue()

Answer 2

You can use a java.util.ArrayList of java.awt.geom.Point2D.Double

Declare the list:

ArrayList<Point2D.Double> points = new ArrayList<>();

Then for each row:

// Read x
// Read y
Point2D.Double p = new Point2D.Double(x, y);
/// And add to the list: 
points.add(p);