java - How to read and write excel file

Question

I want to read and write an Excel file from Java with 3 columns and N rows, printing one string in each cell. Can anyone give me simple code snippet for this? Do I need to use any external lib or does Java have built-in support for it?

I want to do the following:

for(i=0; i <rows; i++)
     //read [i,col1] ,[i,col2], [i,col3]

for(i=0; i<rows; i++)
    //write [i,col1], [i,col2], [i,col3]

question from:https://stackoverflow.com/questions/65848895/how-to-compare-content-of-csv-xls-xlsx-file-extensions-in-java-just-to-check

Answer 1

Try the Apache POI HSSF. Here's an example on how to read 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; // No of rows
    rows = sheet.getPhysicalNumberOfRows();

    int cols = 0; // No of columns
    int tmp = 0;

    // This trick ensures that we get the data properly even if it doesn't start from first few rows
    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;
        }
    }

    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 here
                }
            }
        }
    }
} catch(Exception ioe) {
    ioe.printStackTrace();
}

On the documentation page you also have examples of how to write to excel files.