How to create and update Excel files through Java using JXL library?

Question

Everything I have seen on this issue has been in a main method, however, I am working on a larger system and require a class that can create an Excel workbook, sheets and then write into a cell by the given sheet, row, column and dataToWrite. When the createWorkbook() function runs, however, it creates an empty text document. I suspect it has something to do with the workbook.write() use, however, the documentation is limited and kind of confusing.

//Constructor
public ExcelWriter(String outputFile) {
    this.outputFile=outputFile;
    try {
        workbook=Workbook.createWorkbook(new File(outputFile));
        workbook.write();
    }
    catch(IOException e) {
        System.err.print(e.getMessage());
    }
    sheets=new ArrayList<WritableSheet>();
    sheetCount=0;   
}

public void createSheet(String name) {
    WritableSheet toAdd=workbook.createSheet(name, sheetCount);
    sheets.add(toAdd);
    try {
        workbook.write();
    }
    catch(IOException e) {
        System.err.print(e.getMessage());
    }
    sheetCount++;
}

public void write(int sheet, int row, int col, String data) {
    WritableSheet currentSheet=sheets.get(sheet);
    Label label = new Label(row, col, data);
    try {
        currentSheet.addCell(label);
        workbook.write(); 
    }
    catch(WriteException | IOException e) {
        System.err.print(e.getMessage());
    }
}