BAEL-5204: Change the font color of a cell with Apache POI (#11554)

* BAEL-5204: First commit "Change the font color of a cell with Apache POI"

* BAEL-5204: Create class and unit test

* BAEL-5204: finalize unit test

* BAEL-5204: fix indent

* BAEL-5204: add missing excel template

apache-poi/src/main/java/com/baeldung/poi/excel/cellstyle/CellStyler.java

@@ -0,0 +1,26 @@
+package com.baeldung.poi.excel.cellstyle;
+
+import org.apache.poi.hssf.util.HSSFColor.HSSFColorPredefined;
+import org.apache.poi.ss.usermodel.Cell;
+import org.apache.poi.ss.usermodel.CellStyle;
+import org.apache.poi.ss.usermodel.Font;
+import org.apache.poi.ss.usermodel.HorizontalAlignment;
+import org.apache.poi.ss.usermodel.VerticalAlignment;
+import org.apache.poi.ss.usermodel.Workbook;
+
+public class CellStyler {
+    public CellStyle createWarningColor(Workbook workbook) {
+        CellStyle style = workbook.createCellStyle();
+
+        Font font = workbook.createFont();
+        font.setFontName("Courier New");
+        font.setBold(true);
+        font.setUnderline(Font.U_SINGLE);
+        font.setColor(HSSFColorPredefined.DARK_RED.getIndex());
+        style.setFont(font);
+
+        style.setAlignment(HorizontalAlignment.CENTER);
+        style.setVerticalAlignment(VerticalAlignment.CENTER);
+        return style;
+    }
+}

apache-poi/src/test/java/com/baeldung/poi/excel/cellstyle/CellStylerUnitTest.java

@@ -0,0 +1,52 @@
+package com.baeldung.poi.excel.cellstyle;
+
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.net.URISyntaxException;
+import java.nio.file.Paths;
+
+import org.apache.poi.ss.usermodel.Cell;
+import org.apache.poi.ss.usermodel.CellStyle;
+import org.apache.poi.ss.usermodel.Row;
+import org.apache.poi.ss.usermodel.Sheet;
+import org.apache.poi.ss.usermodel.Workbook;
+import org.apache.poi.xssf.usermodel.XSSFWorkbook;
+import org.junit.Before;
+import org.junit.Test;
+
+public class CellStylerUnitTest {
+    private static String FILE_NAME = "com/baeldung/poi/excel/cellstyle/CellStyle.xlsx";
+    private static final String NEW_FILE_NAME = "CellStyleTest_output.xlsx";
+    private String fileLocation;
+
+    @Before
+    public void setup() throws IOException, URISyntaxException {
+        fileLocation = Paths.get(ClassLoader.getSystemResource(FILE_NAME)
+            .toURI())
+            .toString();
+    }
+
+    @Test
+    public void testApplyWarningColor() throws IOException {
+        Workbook workbook = new XSSFWorkbook(fileLocation);
+        Sheet sheet = workbook.getSheetAt(0);
+        Row row1 = sheet.createRow(0);
+        row1.setHeightInPoints((short) 40);
+
+        CellStyler styler = new CellStyler();
+        CellStyle style = styler.createWarningColor(workbook);
+
+        Cell cell1 = row1.createCell(0);
+        cell1.setCellStyle(style);
+        cell1.setCellValue("Hello");
+
+        Cell cell2 = row1.createCell(1);
+        cell2.setCellStyle(style);
+        cell2.setCellValue("world!");
+
+        FileOutputStream outputStream = new FileOutputStream(NEW_FILE_NAME);
+        workbook.write(outputStream);
+        outputStream.close();
+        workbook.close();
+    }
+}