How to Read and Write Excel Files in Java Using Apache POI?

Reading and Writing Excel Files with Java

Question:

How can you read and write data from an Excel file with Java, printing a string in each cell?

Answer:

To work with Excel files in Java, you can leverage the Apache POI library, specifically its HSSF module. Here's an example of how to read data from an Excel file:

try {
    POIFSFileSystem fs = new POIFSFileSystem(new FileInputStream(file));
    HSSFWorkbook wb = new HSSFWorkbook(fs);
    HSSFSheet sheet = wb.getSheetAt(0);
    HSSFRow row;
    HSSFCell cell;

    int rows; // Number of rows
    rows = sheet.getPhysicalNumberOfRows();

    int cols = 0; // Number of columns
    int tmp = 0;

    // Determine the number of columns
    for (int i = 0; i < 10 || i < rows; i++) {
        row = sheet.getRow(i);
        if (row != null) {
            tmp = sheet.getRow(i).getPhysicalNumberOfCells();
            if (tmp > cols) cols = tmp;
        }
    }

    // Iterate over rows and columns
    for (int r = 0; r < rows; r++) {
        row = sheet.getRow(r);
        if (row != null) {
            for (int c = 0; c < cols; c++) {
                cell = row.getCell((short) c);
                if (cell != null) {
                    // Your code to process the cell value
                }
            }
        }
    }
} catch (Exception ioe) {
    ioe.printStackTrace();
}

The documentation for the Apache POI project also provides examples of how to write data to Excel files.

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