BAEL-5205 Adding a column to an Excel file using Apache POI (#11491)

* BAEL-5205 Adding a column to an Excel file using Apache POI

* BAEL-5205 move the test xls file into the test folder

Co-authored-by: Gang Wu <wugagnca@hotmail.com>

apache-poi-2/src/main/java/com/baeldung/poi/excel/newcolumn/ExcelColumn.java

@@ -0,0 +1,16 @@
+package com.baeldung.poi.excel.newcolumn;
+import org.apache.poi.ss.usermodel.CellType;
+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;
+
+
+public class ExcelColumn {
+
+    public void addColumn(Sheet sheet, CellType cellType) {
+        for (Row currentRow : sheet) {
+            currentRow.createCell(currentRow.getLastCellNum(), cellType);
+        }
+    }
+}

apache-poi-2/src/test/java/com/baeldung/poi/excel/newcolumn/ExcelColumnUnitTest.java

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+package com.baeldung.poi.excel.newcolumn;
+
+import org.apache.poi.ss.usermodel.CellType;
+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;
+
+import java.io.IOException;
+import java.net.URISyntaxException;
+import java.nio.file.Paths;
+
+import static org.junit.Assert.assertEquals;
+
+public class ExcelColumnUnitTest {
+    private static final String FILE_NAME = "newColumnTest.xlsx";
+    private String fileLocation;
+
+    @Before
+    public void setup() throws URISyntaxException {
+        fileLocation = Paths.get(ClassLoader.getSystemResource(FILE_NAME).toURI()).toString();
+    }
+
+    @Test
+    public void givenExistingRows_whenAddNewColumn_thenRowColumnNumberIncreased() throws IOException {
+        Workbook workbook = new XSSFWorkbook(fileLocation);
+        Sheet sheet = workbook.getSheetAt(0);
+        Row row = sheet.getRow(0);
+        assertEquals(5, row.getLastCellNum());
+
+        ExcelColumn excelColumn = new ExcelColumn();
+        excelColumn.addColumn(sheet, CellType.STRING);
+        assertEquals(6, row.getLastCellNum());
+
+        workbook.close();
+    }
+
+}