Aspose.Cells FOSS
Java
How to Work with Cells Core in Java

How to Work with Cells Core in Java

Aspose.Cells FOSS for Java builds Excel .xlsx workbooks in pure Java through three core classes: Workbook (the file), Worksheet (a sheet inside it), and Cells/Cell (the grid of values and their styling). This guide walks through the complete core workflow — create a workbook, name a worksheet, write values into cells, read them back, apply basic styling, and save the result.

Step-by-Step Guide

Step 1: Install the Package 

<dependency>
  <groupId>org.aspose</groupId>
  <artifactId>aspose-cells-foss</artifactId>
  <version>26.7.0</version>
</dependency>

Step 2: Import Required Classes 

import org.aspose.cells_foss.Cell;
import org.aspose.cells_foss.Style;
import org.aspose.cells_foss.Workbook;
import org.aspose.cells_foss.Worksheet;

Step 3: Create a Workbook and Name a Worksheet

Workbook implements the standard Java auto-closeable resource contract, so a try-with-resources block releases its internal buffers once the sheet is saved. Workbook.getWorksheets() returns the sheet collection; a brand-new workbook already contains one sheet at index 0, reached with WorksheetCollection.get(0):

try (Workbook workbook = new Workbook()) {
    Worksheet sheet = workbook.getWorksheets().get(0);
    sheet.setName("Report");
}

Step 4: Write Values into Cells

Worksheet.getCells() returns the Cells collection for the sheet. Cells.get(cellName) resolves an A1-style reference to a Cell, and Cell.putValue(value) accepts a text string, number, or boolean:

sheet.getCells().get("A1").putValue("Revenue");
sheet.getCells().get("B1").putValue(12500.75);

Step 5: Read Values Back

Cell.getValue() returns the raw stored value; Cell.getStringValue() and Cell.getDisplayStringValue() return formatted text representations:

Cell revenueCell = sheet.getCells().get("B1");
System.out.println(revenueCell.getStringValue());

Step 6: Apply Basic Cell Styling

Cell.getStyle() returns a copy of the cell’s current Style; modify it through Style.getFont() and Style.setCustom(formatCode), then write it back with Cell.setStyle(style):

Cell total = sheet.getCells().get("B1");
Style style = total.getStyle();
style.getFont().setBold(true);
style.setCustom("#,##0.00");
total.setStyle(style);

sheet.getCells().getRows().get(0).setHeight(22.0);
sheet.getCells().getColumns().get(1).setWidth(14.5);

Step 7: Save the Workbook

Workbook.save(fileName) writes the current content to an .xlsx file:

workbook.save("report.xlsx");

Common Issues and Fixes

Styling changes do not appear after calling setStyle(). Cell.getStyle() returns a detached copy of the style, not a live reference. Always call Cell.setStyle(style) again after modifying the returned object, as shown in Step 6 — mutating the copy alone has no effect on the cell.

putValue() stores the wrong type. Cell.putValue(value) has several overloads; passing a boxed number where a String was intended (or vice versa) changes how Excel renders the cell. Check Cell.getType() after loading a workbook if a value looks different than expected.

Row or column index is out of range. RowCollection.get(index) and ColumnCollection.get(index) create the row/column metadata entry at that index if it does not exist yet (rows and columns are sparse); passing a negative index throws an exception. Confirm the index is zero-based and non-negative.

Workbook.save() throws an exception mentioning “at least one worksheet”. WorksheetCollection.removeAt(...) can remove the last remaining sheet. A workbook must retain at least one worksheet before Workbook.save(...) is called.

Changes are lost after the try-with-resources block exits. Call Workbook.save(fileName) (or one of its stream overloads) before the try-with-resources block closes — Workbook.close() releases internal state and does not implicitly save.

Frequently Asked Questions

Does a new Workbook() start with any worksheets?

Yes. new Workbook() creates a workbook with one worksheet already present at index 0 — there is no need to call WorksheetCollection.add() before writing to the first sheet.

How do I add more worksheets?

Call WorksheetCollection.add() (adds a sheet with a default name) or WorksheetCollection.add(sheetName) to choose the name directly; both return the new sheet’s index.

How do I reference a cell by row/column numbers instead of an A1 string?

Cells.get(row, column) accepts zero-based row and column integers and returns the same Cell as Cells.get(cellName).

What is the difference between getValue() and getStringValue()?

Cell.getValue() returns the underlying typed value as a plain Java object (a number, text, or boolean). Cell.getStringValue() returns the raw text form, while Cell.getDisplayStringValue() applies the cell’s number format before returning text — use it when the formatted on-screen representation matters.

See Also