import org.apache.poi.hssf.usermodel.*;
import org.apache.poi.xssf.usermodel.XSSFCell;
import org.apache.poi.xssf.usermodel.XSSFRow;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
import java.io.*;
import java.text.DecimalFormat;
import java.text.SimpleDateFormat;
 
import java.util.ArrayList;
public class ExcelUtil {

    //預設單元格內容為數字時格式
private static DecimalFormat df = new DecimalFormat("0");
// 預設單元格格式化日期字串
private static SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
// 格式化數字
private static DecimalFormat nf = new DecimalFormat("0.00");
    public static 
 
ArrayList<ArrayList<Object>> readExcel(File file){
        if(file == null){
            return null;
}
        if(file.getName().endsWith("xlsx")){
            //處理ecxel2007
return readExcel2007(file);
}else{
            //處理ecxel2003
return readExcel2003(file);
}
    }

    /*
     * @return 將返回結果儲存在
 
ArrayList內，儲存結構與二位陣列類似     * lists.get(0).get(0)表示過去Excel中0行0列單元格     */
public static ArrayList<ArrayList<Object>> readExcel2003(File file){
        try{
            ArrayList<ArrayList<Object>> rowList = new ArrayList<ArrayList<Object>>();
ArrayList<Object> colList;
HSSFWorkbook wb = new HSSFWorkbook(new FileInputStream(file));
HSSFSheet sheet = wb.getSheetAt(0);
HSSFRow row;
HSSFCell cell;
Object value;
            for(int i = sheet.getFirstRowNum() , rowCount = 0; rowCount < sheet.getPhysicalNumberOfRows() ; i++ ){
                row = sheet.getRow(i);
colList = new ArrayList<Object>();
                if(row == null){
                    //當讀取行為空時
if(i != sheet.getPhysicalNumberOfRows()){//判斷是否是最後一行
rowList.add(colList);
}
                    continue;
}else{
                    rowCount++;
}
                for( int j = row.getFirstCellNum() ; j <= row.getLastCellNum() ;j++){
                    cell = row.getCell(j);
                    if(cell == null || cell.getCellType() == HSSFCell.CELL_TYPE_BLANK){
                        //當該單元格為空
if(j != row.getLastCellNum()){//判斷是否是該行中最後一個單元格
colList.add("");
}
                        continue;
}
                    switch(cell.getCellType()){
                        case XSSFCell.CELL_TYPE_STRING:
                            System.out.println(i + "行" + j + " 列 is String type");
value = cell.getStringCellValue();
                            break;
                        case XSSFCell.CELL_TYPE_NUMERIC:
                            if ("@".equals(cell.getCellStyle().getDataFormatString())) {
                                value = df.format(cell.getNumericCellValue());
} else if ("General".equals(cell.getCellStyle()
                                    .getDataFormatString())) {
                                value = nf.format(cell.getNumericCellValue());
} else {
                                value = sdf.format(HSSFDateUtil.getJavaDate(cell
                                        .getNumericCellValue()));
}
                            System.out.println(i + "行" + j
                                    + " 列 is Number type ; DateFormt:"
+ value.toString());
                            break;
                        case XSSFCell.CELL_TYPE_BOOLEAN:
                            System.out.println(i + "行" + j + " 列 is Boolean type");
value = Boolean.valueOf(cell.getBooleanCellValue());
                            break;
                        case XSSFCell.CELL_TYPE_BLANK:
                            System.out.println(i + "行" + j + " 列 is Blank type");
value = "";
                            break;
                        default:
                            System.out.println(i + "行" + j + " 列 is default type");
value = cell.toString();
}// end switch
colList.add(value);
}//end for j
rowList.add(colList);
}//end for i
return rowList;
}catch(Exception e){
            return null;
}
    }

    public static ArrayList<ArrayList<Object>> readExcel2007(File file){
        try{
            ArrayList<ArrayList<Object>> rowList = new ArrayList<ArrayList<Object>>();
ArrayList<Object> colList;
XSSFWorkbook wb = new XSSFWorkbook(new FileInputStream(file));
XSSFSheet sheet = wb.getSheetAt(0);
XSSFRow row;
XSSFCell cell;
Object value;
            for(int i = sheet.getFirstRowNum() , rowCount = 0; rowCount < sheet.getPhysicalNumberOfRows() ; i++ ){
                row = sheet.getRow(i);
colList = new ArrayList<Object>();
                if(row == null){
                    //當讀取行為空時
if(i != sheet.getPhysicalNumberOfRows()){//判斷是否是最後一行
rowList.add(colList);
}
                    continue;
}else{
                    rowCount++;
}
                for( int j = row.getFirstCellNum() ; j <= row.getLastCellNum() ;j++){
                    cell = row.getCell(j);
                    if(cell == null || cell.getCellType() == HSSFCell.CELL_TYPE_BLANK){
                        //當該單元格為空
if(j != row.getLastCellNum()){//判斷是否是該行中最後一個單元格
colList.add("");
}
                        continue;
}
                    switch(cell.getCellType()){
                        case XSSFCell.CELL_TYPE_STRING:
                            System.out.println(i + "行" + j + " 列 is String type");
value = cell.getStringCellValue();
                            break;
                        case XSSFCell.CELL_TYPE_NUMERIC:
                            if ("@".equals(cell.getCellStyle().getDataFormatString())) {
                                value = df.format(cell.getNumericCellValue());
} else if ("General".equals(cell.getCellStyle()
                                    .getDataFormatString())) {
                                value = nf.format(cell.getNumericCellValue());
} else {
                                value = sdf.format(HSSFDateUtil.getJavaDate(cell
                                        .getNumericCellValue()));
}
                            System.out.println(i + "行" + j
                                    + " 列 is Number type ; DateFormt:"
+ value.toString());
                            break;
                        case XSSFCell.CELL_TYPE_BOOLEAN:
                            System.out.println(i + "行" + j + " 列 is Boolean type");
value = Boolean.valueOf(cell.getBooleanCellValue());
                            break;
                        case XSSFCell.CELL_TYPE_BLANK:
                            System.out.println(i + "行" + j + " 列 is Blank type");
value = "";
                            break;
                        default:
                            System.out.println(i + "行" + j + " 列 is default type");
value = cell.toString();
}// end switch
colList.add(value);
}//end for j
rowList.add(colList);
}//end for i
return rowList;
}catch(Exception e){
            System.out.println("exception");
            return null;
}
    }


    public static void writeExcel(ArrayList<ArrayList<Object>> result, String path) {
        if (result == null) {
            return;
}
        HSSFWorkbook wb = new HSSFWorkbook();
HSSFSheet sheet = wb.createSheet("sheet1");
        for (int i = 0; i < result.size(); i++) {
            HSSFRow row = sheet.createRow(i);
            if (result.get(i) != null) {
                for (int j = 0; j < result.get(i).size(); j++) {
                    HSSFCell cell = row.createCell(j);
cell.setCellValue(result.get(i).get(j).toString());
//                    if (i > 0 && j == 3) {//第二列複製到第四列
//                        cell.setCellValue(result.get(i).get(1).toString());
//                    } else {
//                        cell.setCellValue(result.get(i).get(j).toString());
//                    }
}
            }
        }
        ByteArrayOutputStream os = new ByteArrayOutputStream();
        try {
            wb.write(os);
} catch (IOException e) {
            e.printStackTrace();
}
        byte[] content = os.toByteArray();
File file = new File(path);//Excel檔案生成後儲存的位置。
OutputStream fos = null;
        try {
            fos = new FileOutputStream(file);
fos.write(content);
os.close();
fos.close();
} catch (Exception e) {
            e.printStackTrace();
}
    }


    public static DecimalFormat getDf() {
        return df;
}
    public static void setDf(DecimalFormat df) {
        ExcelUtil.df = df;
}
    public static SimpleDateFormat getSdf() {
        return sdf;
}
    public static void setSdf(SimpleDateFormat sdf) {
        ExcelUtil.sdf = sdf;
}
    public static DecimalFormat getNf() {
        return nf;
}
    public static void setNf(DecimalFormat nf) {
        ExcelUtil.nf = nf;
}

    public static void main(String[] args) {
        File file = new File("D:/a.xls");
ArrayList<ArrayList<Object>> result = ExcelUtil.readExcel(file);
        for(int i = 0 ;i < result.size() ;i++){
            for(int j = 0;j<result.get(i).size(); j++){
                System.out.println(i+"行 "+j+"列  "+ result.get(i).get(j).toString());
}
        }
        ExcelUtil.writeExcel(result,"D:/b.xls");
}

}

引用到的jar：

<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi-ooxml</artifactId>
    <version>3.11-beta1</version>
</dependency>