log.info cell.getNumericCellValue()
log.info cell.getStringCellValue()

import org.apache.poi.xssf.usermodel.*


def fs = new FileInputStream("C:\File\Book2.xlsx")
def wb = new XSSFWorkbook(fs)
def ws = wb.getSheet("Sheet1")
def r = ws.getPhysicalNumberOfRows()


for(def i=0; i<r; i++){

    def row = ws.getRow(i)
    def c = row.getPhysicalNumberOfCells()

    for (def j=0; j<c; j++) {

        def cell = row.getCell(j)

         log.info cell.getStringCellValue()
    }
}

java.lang.illegalStateException:Cannot get a STRING value from a NUMERIC cell

java.lang.illegalStateException:Cannot get a NUMERIC value from a STRING cell