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org.apache.poi 4.0 removed the XSSFColor constructor that just uses java.awt.Color. In org.apache.poi 3.7 it was very easy to create the object by just writing

Color inputColor = Color.RED;
XSSFColor test = new XSSFColor(inputColor);

However, this constructor no longer works in 4.0. The documentation at https://poi.apache.org/apidocs/dev/org/apache/poi/xssf/usermodel/XSSFColor.html shows several other constructors, but ideally i want to change as few lines as possible.

So, my question is, what is the best way to create an XSSFColor from a java.awt.Color now (in apache poi 4.0)?

As requested in the comments, here is my test code using the suggestion style.setFillForegroundColor(new XSSFColor(java.awt.Color.RED, null));
Opening this with LibreOffice 6.1 yields an Error (Attempt to repair, which then fails). Commented out the POI 3.7 version which works normally.

@Test
public void testPOI40() throws FileNotFoundException, IOException 
 Workbook workbook = new XSSFWorkbook();
 XSSFSheet fSheet = (XSSFSheet) workbook.createSheet("new Sheet");
 XSSFRow hRow = fSheet.createRow((short) 0);
 //header
 String astrHeaders = new String"Header1", "Header2", "Header3", "Header4";
 for (int col = 0; col < astrHeaders.length; col++) 
 XSSFCell cell = hRow.createCell((short) col);
 XSSFCellStyle tempHeaderStyle = (XSSFCellStyle) workbook.createCellStyle();
 tempHeaderStyle.setFillForegroundColor(IndexedColors.GREY_25_PERCENT.getIndex());
 tempHeaderStyle.setFillPattern(FillPatternType.SOLID_FOREGROUND);
 cell.setCellValue(astrHeaders[col]);
 cell.setCellStyle(tempHeaderStyle);
 
 //body
 Double astrContent = new Double1.3, 0.3, 0.87, 1.0; 
 Color colors = new Color Color.RED,Color.BLUE,Color.WHITE,Color.GREEN; 
 XSSFRow fRow = fSheet.createRow((short) 1);
 for (int iCol = 0; iCol < 4; iCol++) 
 XSSFCell cell = fRow.createCell((short) iCol);
 XSSFCellStyle tempBodyStyle = (XSSFCellStyle) workbook.createCellStyle();
 cell.setCellValue(astrContent[iCol]);
 //working with POI 3.17
 //tempBodyStyle.setFillForegroundColor(new XSSFColor(colors[iCol]));
 tempBodyStyle.setFillForegroundColor(new XSSFColor(colors[iCol],null));
 tempBodyStyle.setFillPattern(FillPatternType.SOLID_FOREGROUND);
 cell.setCellStyle(tempBodyStyle);
 
 FileOutputStream fileOut = new FileOutputStream(new File("testfile.xlsx"));
 BufferedOutputStream bos = new BufferedOutputStream(fileOut);
 workbook.write(bos);
 fileOut.close();

Solution:

Replaced fileout.close(); with bos.close(); and it works. So tempBodyStyle.setFillForegroundColor(new XSSFColor(Color.RED,null)); as suggested in the comments by Alex Richter is a good solution & will accept this as answer.

If you are wrapping the FileOutputStream in an BufferedOutputStream but do closing then only the inner FileOutputStream but not the BufferedOutputStream, then the BufferedOutputStream remains open and the file will not have all bytes in.

That's why the damaging of the file.

So the damaging has noting to do with constructing the XSSFColor. The constructor style.setFillForegroundColor(new XSSFColor(java.awt.Color.RED, null)); works.

Do instead:

...
FileOutputStream fileOut = new FileOutputStream(new File("testfile.xlsx"));
BufferedOutputStream bos = new BufferedOutputStream(fileOut);
workbook.write(bos); 
bos.close();
workbook.close();
...

It might had worked in former apache poi versions because XSSFWorkbook.write had closed all streams when it was ready. This it does not more. And this is correct because write should not closing streams.

But since POIXMLDocument implements java.io.Closeable at least workbook.close() should closing all streams. But that also it does not. So explicitly closing all streams is necessary in apache poi 4.0.0.