Create a styled Excel spreadsheet with Groovy and Apache POI

excel.groovy

@Grab( 'org.apache.poi:poi:3.9' )
import static org.apache.poi.ss.usermodel.CellStyle.*
import static org.apache.poi.ss.usermodel.IndexedColors.*
import org.apache.poi.hssf.usermodel.HSSFWorkbook

new HSSFWorkbook().with { workbook ->
  def styles = [ LIGHT_BLUE, LIGHT_GREEN, LIGHT_ORANGE ].collect { color ->
    createCellStyle().with { style ->
      fillForegroundColor = color.index
      fillPattern = SOLID_FOREGROUND
      style
    }
  }
  createSheet( 'Output' ).with { sheet ->
    (0..4).each { rownum ->
      createRow( rownum ).with { row ->
        (0..4).each { colnum ->
          createCell( colnum ).with { cell ->
            setCellValue( "[$colnum,$rownum]" )
            cellStyle = styles[ ( ( rownum * 5 ) + colnum ) % styles.size() ]
          }
        }
      }
    }
    new File( '/tmp/test.xls' ).withOutputStream { os ->
      write( os )
    }
  }
}