java读取百万行csv,excel的处理_java 多线程读取几万行csv文件

上篇文章中使用opencsv包读取csv格式，如果csv文件内容过大，会导致jvm产生oom的问题，顾修改代码如下
reader = new CSVReaderBuilder(new InputStreamReader(input, fileEncode)).build()
//记录column
ArrayList columns = new ArrayList<>();
int columnIndex = 0;
String[] rowData = reader.readNext();
复制代码由之前readall 形式改为readnext()一行行读取形式，按行加载至arrayList,按需处理完在对list进行clear()操作，释放内存，再进行readnext加载。。
excel篇：之前采用 poi用户模式读取excel，会极大的消耗内存,查阅资料poi官方推荐使用事件模式读取贴上代码
xls

import org.apache.logging.log4j.LogManager;import org.apache.logging.log4j.Logger;import org.apache.poi.hssf.eventusermodel.*;import org.apache.poi.hssf.eventusermodel.dummyrecord.LastCellOfRowDummyRecord;import org.apache.poi.hssf.eventusermodel.dummyrecord.MissingCellDummyRecord;import org.apache.poi.hssf.model.HSSFFormulaParser;import org.apache.poi.hssf.record.*;import org.apache.poi.hssf.usermodel.HSSFDataFormatter;import org.apache.poi.hssf.usermodel.HSSFWorkbook;import org.apache.poi.poifs.filesystem.POIFSFileSystem;import java.io.FileInputStream;import java.util.ArrayList;import java.util.List;/** *  @desc 用于解决.xls2003版本大数据量问题 **/public class ExcelXlsReader implements HSSFListener {    private static final Logger logger = LogManager.getLogger(ExcelXlsxReaderWithDefaultHandler.class);    private int minColums = -1;    private POIFSFileSystem fs;    /**     * 总行数     */    private int totalRows = 0;    /**     * 上一行row的序号     */    private int lastRowNumber;    /**     * 上一单元格的序号     */    private int lastColumnNumber;    /**     * 是否输出formula，还是它对应的值     */    private boolean outputFormulaValues = true;    /**     * 用于转换formulas     */    private EventWorkbookBuilder.SheetRecordCollectingListener workbookBuildingListener;    //excel2003工作簿    private HSSFWorkbook stubWorkbook;    private SSTRecord sstRecord;    private FormatTrackingHSSFListener formatListener;    private final HSSFDataFormatter formatter = new HSSFDataFormatter();    /**     * 文件的绝对路径     */    private String filePath = "";    //表索引    private int sheetIndex = 0;    private BoundSheetRecord[] orderedBSRs;    @SuppressWarnings("unchecked")    private ArrayList boundSheetRecords = new ArrayList();    private int nextRow;    private int nextColumn;    private boolean outputNextStringRecord;    //当前行    private int curRow = 0;    //存储一行记录所有单元格的容器    private ArrayList<String> cellList = new ArrayList<String>();    /**     *     */    private List<ArrayList<String>> cellLists = new ArrayList<>();    /**     *   */    private ArrayList<String> columnList = new ArrayList<>();    /**     * 判断整行是否为空行的标记     */    private boolean flag = false;    @SuppressWarnings("unused")    private String sheetName;    private String companyId = "";    private String containerLogId = "";    private JSONObject config;    private int resultRows = 0;    /**     * 遍历excel下所有的sheet     *     * @param fileName     * @throws Exception     */    public int process(String fileName, String companyId, String containerLogId, JSONObject config) throws Exception {        filePath = fileName;        this.companyId = companyId;        this.containerLogId = containerLogId;        this.config = config;        this.fs = new POIFSFileSystem(new FileInputStream(fileName));        MissingRecordAwareHSSFListener listener = new MissingRecordAwareHSSFListener(this);        formatListener = new FormatTrackingHSSFListener(listener);        HSSFEventFactory factory = new HSSFEventFactory();        HSSFRequest request = new HSSFRequest();        if (outputFormulaValues) {            request.addListenerForAllRecords(formatListener);        } else {            workbookBuildingListener = new EventWorkbookBuilder.SheetRecordCollectingListener(formatListener);            request.addListenerForAllRecords(workbookBuildingListener);        }        factory.processWorkbookEvents(request, fs);        if (cellLists.size() > 0) {  cellLists.clear();        }              return resultRows; //返回该excel文件的总行数，不包括首列和空行    }    /**     * HSSFListener 监听方法，处理Record     * 处理每个单元格     *     * @param record     */    @SuppressWarnings("unchecked")    public void processRecord(Record record) {        try {            int thisRow = -1;            int thisColumn = -1;            String thisStr = null;            String value = null;            switch (record.getSid()) {                case BoundSheetRecord.sid:                    boundSheetRecords.add(record);                    break;                case BOFRecord.sid: //开始处理每个sheet                    BOFRecord br = (BOFRecord) record;                    if (br.getType() == BOFRecord.TYPE_WORKSHEET) {                        //如果有需要，则建立子工作簿                        if (workbookBuildingListener != null && stubWorkbook == null) {                            stubWorkbook = workbookBuildingListener.getStubHSSFWorkbook();                        }                        if (orderedBSRs == null) {                            orderedBSRs = BoundSheetRecord.orderByBofPosition(boundSheetRecords);                        }                        sheetName = orderedBSRs[sheetIndex].getSheetname();                        sheetIndex++;                    }                    break;                case SSTRecord.sid:                    sstRecord = (SSTRecord) record;                    break;                case BlankRecord.sid: //单元格为空白                    BlankRecord brec = (BlankRecord) record;                    thisRow = brec.getRow();                    thisColumn = brec.getColumn();                    thisStr = "";                    cellList.add(thisColumn, thisStr);                    break;                case BoolErrRecord.sid: //单元格为布尔类型                    BoolErrRecord berec = (BoolErrRecord) record;                    thisRow = berec.getRow();                    thisColumn = berec.getColumn();                    thisStr = berec.getBooleanValue() + "";                    cellList.add(thisColumn, thisStr);                    checkRowIsNull(thisStr);  //如果里面某个单元格含有值，则标识该行不为空行                    break;                case FormulaRecord.sid://单元格为公式类型                    FormulaRecord frec = (FormulaRecord) record;                    thisRow = frec.getRow();                    thisColumn = frec.getColumn();                    if (outputFormulaValues) {                        if (Double.isNaN(frec.getValue())) {                            outputNextStringRecord = true;                            nextRow = frec.getRow();                            nextColumn = frec.getColumn();                        } else {                            thisStr = '"' + HSSFFormulaParser.toFormulaString(stubWorkbook,                                    frec.getParsedExpression()) + '"';                        }                    } else {                        thisStr =                                '"' + HSSFFormulaParser.toFormulaString(stubWorkbook, frec.getParsedExpression()) + '"';                    }                    cellList.add(thisColumn, thisStr);                    checkRowIsNull(thisStr);  //如果里面某个单元格含有值，则标识该行不为空行                    break;                case StringRecord.sid: //单元格中公式的字符串                    if (outputNextStringRecord) {                        StringRecord srec = (StringRecord) record;                        thisStr = srec.getString();                        thisRow = nextRow;                        thisColumn = nextColumn;                        outputNextStringRecord = false;                    }                    break;                case LabelRecord.sid:                    LabelRecord lrec = (LabelRecord) record;                    curRow = thisRow = lrec.getRow();                    thisColumn = lrec.getColumn();                    value = lrec.getValue().trim();                    value = value.equals("") ? "" : value;                    cellList.add(thisColumn, value);                    checkRowIsNull(value);  //如果里面某个单元格含有值，则标识该行不为空行                    break;                case LabelSSTRecord.sid: //单元格为字符串类型                    LabelSSTRecord lsrec = (LabelSSTRecord) record;                    curRow = thisRow = lsrec.getRow();                    thisColumn = lsrec.getColumn();                    if (sstRecord == null) {                        cellList.add(thisColumn, "");                    } else {                        value = sstRecord.getString(lsrec.getSSTIndex()).toString().trim();                        value = value.equals("") ? "" : value;                        cellList.add(thisColumn, value);                        checkRowIsNull(value);  //如果里面某个单元格含有值，则标识该行不为空行                    }                    break;                case NumberRecord.sid: //单元格为数字类型                    NumberRecord numrec = (NumberRecord) record;                    curRow = thisRow = numrec.getRow();                    thisColumn = numrec.getColumn();                    //第一种方式                    //value = formatListener.formatNumberDateCell(numrec).trim();//这个被写死，采用的m/d/yy h:mm格式，不符合要求                    //第二种方式，参照formatNumberDateCell里面的实现方法编写                    Double valueDouble = ((NumberRecord) numrec).getValue();                    String formatString = formatListener.getFormatString(numrec);                    if (formatString.contains("m/d/yy") || formatString.contains("yyyy/mm/dd") || formatString.contains(                            "yyyy/m/d")) {                        formatString = "yyyy-MM-dd hh:mm:ss";                    }                    int formatIndex = formatListener.getFormatIndex(numrec);                    value = formatter.formatRawCellContents(valueDouble, formatIndex, formatString).trim();                    value = value.equals("") ? "" : value;                    //向容器加入列值                    cellList.add(thisColumn, value);                    checkRowIsNull(value);  //如果里面某个单元格含有值，则标识该行不为空行                    break;                default:                    break;            }            //遇到新行的操作            if (thisRow != -1 && thisRow != lastRowNumber) {                lastColumnNumber = -1;            }            //空值的操作            if (record instanceof MissingCellDummyRecord) {                MissingCellDummyRecord mc = (MissingCellDummyRecord) record;                curRow = thisRow = mc.getRow();                thisColumn = mc.getColumn();                cellList.add(thisColumn, "");            }            //更新行和列的值            if (thisRow > -1)                lastRowNumber = thisRow;            if (thisColumn > -1)                lastColumnNumber = thisColumn;            //行结束时的操作            if (record instanceof LastCellOfRowDummyRecord) {                if (minColums > 0) {                    //列值重新置空                    if (lastColumnNumber == -1) {                        lastColumnNumber = 0;                    }                }                lastColumnNumber = -1;                if (flag && curRow == 0) {                    columnList = cellList;                }                if (flag && curRow != 0) { //该行不为空行且该行不是第一行，发送（第一行为列名，不需要）                    cellLists.add(cellList);                    totalRows++;                    if (totalRows != 0 && totalRows % 500 == 0) {                       cellLists.clear();                    }                }                //清空容器                cellList = new ArrayList<>();                flag = false;            }        } catch (Exception ex) {            logger.error(ex.getMessage(), ex);        }    }    /**     * 如果里面某个单元格含有值，则标识该行不为空行     *     * @param value     */    public void checkRowIsNull(String value) {        if (value != null && !"".equals(value)) {            flag = true;        }    }}


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xlsx

import cn.ifuli.ciq.dataworks.api.Import.flexdata.rpcClient.Client;import com.alibaba.fastjson.JSON;import com.alibaba.fastjson.JSONObject;import org.apache.logging.log4j.LogManager;import org.apache.logging.log4j.Logger;import org.apache.poi.openxml4j.opc.OPCPackage;import org.apache.poi.ss.usermodel.BuiltinFormats;import org.apache.poi.ss.usermodel.DataFormatter;import org.apache.poi.xssf.eventusermodel.XSSFReader;import org.apache.poi.xssf.model.SharedStringsTable;import org.apache.poi.xssf.model.StylesTable;import org.apache.poi.xssf.usermodel.XSSFCellStyle;import org.apache.poi.xssf.usermodel.XSSFRichTextString;import org.xml.sax.Attributes;import org.xml.sax.InputSource;import org.xml.sax.SAXException;import org.xml.sax.XMLReader;import org.xml.sax.helpers.DefaultHandler;import org.xml.sax.helpers.XMLReaderFactory;import java.io.InputStream;import java.math.BigInteger;import java.util.ArrayList;import java.util.List;import java.util.regex.Pattern;/** *@desc POI读取excel有两种模式，一种是用户模式，一种是事件驱动模式 * 采用SAX事件驱动模式解决XLSX文件，可以有效解决用户模式内存溢出的问题， * 该模式是POI官方推荐的读取大数据的模式， * 在用户模式下，数据量较大，Sheet较多，或者是有很多无用的空行的情况下，容易出现内存溢出 * <p> * 用于解决.xlsx2007版本大数据量问题 **/public class ExcelXlsxReaderWithDefaultHandler extends DefaultHandler {    private static final Logger logger = LogManager.getLogger(ExcelXlsxReaderWithDefaultHandler.class);    /**     * 单元格中的数据可能的数据类型     */    enum CellDataType {        BOOL, ERROR, FORMULA, INLINESTR, SSTINDEX, NUMBER, DATE, NULL    }    /**     * 共享字符串表     */    private SharedStringsTable sst;    /**     * 上一次的索引值     */    private String lastIndex;    /**     * 文件的绝对路径     */    private String filePath = "";    /**     * 工作表索引     */    private int sheetIndex = 0;    /**     * sheet名     */    private String sheetName = "";    /**     * 总行数     */    private int totalRows = 0;    /**     * 一行内cell集合     */    private ArrayList<String> cellList = new ArrayList<>();    /**     *    */    private List<ArrayList<String>> cellLists = new ArrayList<>();    /**     *    */    private ArrayList<String> columnList = new ArrayList<>();    /**     * 判断整行是否为空行的标记     */    private boolean flag = false;    /**     * 当前行     */    private int curRow = 1;    /**     * 当前列     */    private int curCol = 0;    /**     * T元素标识     */    private boolean isTElement;    /**     * 判断上一单元格是否为文本空单元格     */    private boolean endElementFlag = false;    private boolean charactersFlag = false;    /**     * 异常信息，如果为空则表示没有异常     */    private String exceptionMessage;    /**     * 单元格数据类型，默认为字符串类型     */    private CellDataType nextDataType = CellDataType.SSTINDEX;    private final DataFormatter formatter = new DataFormatter();    /**     * 单元格日期格式的索引     */    private short formatIndex;    /**     * 日期格式字符串     */    private String formatString;    //定义前一个元素和当前元素的位置，用来计算其中空的单元格数量，如A6和A8等    private String preRef = null, ref = null;    //定义该文档一行最大的单元格数，用来补全一行最后可能缺失的单元格    private String maxRef = null;    /**     * 单元格     */    private StylesTable stylesTable;    private String companyId = "";    private String containerLogId = "";    private JSONObject config;    private int resultRows = 0;    //private int testResult = 0;    /**     * 遍历工作簿中所有的电子表格     * 并缓存在mySheetList中     *     * @param filename     * @throws Exception     */    public int process(String filename, String companyId, String containerLogId, JSONObject config) throws Exception {        filePath = filename;        this.companyId = companyId;        this.containerLogId = containerLogId;        this.config = config;        OPCPackage pkg = OPCPackage.open(filename);        XSSFReader xssfReader = new XSSFReader(pkg);        stylesTable = xssfReader.getStylesTable();        SharedStringsTable sst = xssfReader.getSharedStringsTable();        XMLReader parser = XMLReaderFactory.createXMLReader("org.apache.xerces.parsers.SAXParser");        this.sst = sst;        parser.setContentHandler(this);        XSSFReader.SheetIterator sheets = (XSSFReader.SheetIterator) xssfReader.getSheetsData();//        while (sheets.hasNext()) { //遍历sheet        curRow = 1; //标记初始行为第一行        sheetIndex++;        InputStream sheet = sheets.next(); //sheets.next()和sheets.getSheetName()不能换位置，否则sheetName报错        sheetName = sheets.getSheetName();        InputSource sheetSource = new InputSource(sheet);        parser.parse(sheetSource); //解析excel的每条记录，在这个过程中startElement()、characters()、endElement()这三个函数会依次执行        sheet.close();//        }        if (cellLists.size() > 0) {     cellLists.clear();        }        //组装数据并发送        UserData data = new UserData();        data.setCompanyId(companyId);        data.setContainerLogId(containerLogId);        data.setUserDataList(new ArrayList<>());        data.setIsEnd(true);                return resultRows; //返回该excel文件的总行数，不包括首列和空行    }    /**     * 第一个执行     *     * @param uri     * @param localName     * @param name     * @param attributes     * @throws SAXException     */    @Override    public void startElement(String uri, String localName, String name, Attributes attributes) throws SAXException {        //c => 单元格        if ("c".equals(name)) {            //前一个单元格的位置            if (preRef == null) {                preRef = attributes.getValue("r");            } else {                //判断前一次是否为文本空字符串，true则表明不是文本空字符串，false表明是文本空字符串跳过把空字符串的位置赋予preRef                if (endElementFlag) {                    preRef = ref;                }            }            //当前单元格的位置            ref = attributes.getValue("r");            //设定单元格类型            this.setNextDataType(attributes);            endElementFlag = false;            charactersFlag = false;        }        //当元素为t时        if ("t".equals(name)) {            isTElement = true;        } else {            isTElement = false;        }        //置空        lastIndex = "";    }    /**     * 第二个执行     * 得到单元格对应的索引值或是内容值     * 如果单元格类型是字符串、INLINESTR、数字、日期，lastIndex则是索引值     * 如果单元格类型是布尔值、错误、公式，lastIndex则是内容值     *     * @param ch     * @param start     * @param length     * @throws SAXException     */    @Override    public void characters(char[] ch, int start, int length) throws SAXException {        charactersFlag = true;        lastIndex += new String(ch, start, length);    }    /**     * 第三个执行     *     * @param uri     * @param localName     * @param name     * @throws SAXException     */    @Override    public void endElement(String uri, String localName, String name) throws SAXException {        try {            //t元素也包含字符串            if (isTElement) {//这个程序没经过                //将单元格内容加入rowlist中，在这之前先去掉字符串前后的空白符                String value = lastIndex.trim();                cellList.add(curCol, value);                endElementFlag = true;                curCol++;                isTElement = false;                //如果里面某个单元格含有值，则标识该行不为空行                if (value != null && !"".equals(value)) {                    flag = true;                }            } else if ("v".equals(name)) {                //v => 单元格的值，如果单元格是字符串，则v标签的值为该字符串在SST中的索引                String value = this.getDataValue(lastIndex.trim(), "");//根据索引值获取对应的单元格值                //补全单元格之间的空单元格                if (!ref.equals(preRef)) {                    int len = countNullCell(ref, preRef);                    for (int i = 0; i < len; i++) {                        cellList.add(curCol, "");                        curCol++;                    }                }                cellList.add(curCol, value);                curCol++;                endElementFlag = true;                //如果里面某个单元格含有值，则标识该行不为空行                if (value != null && !"".equals(value)) {                    flag = true;                }            } else {                //如果标签名称为row，这说明已到行尾，调用optRows()方法                if ("row".equals(name)) {                    //默认第一行为表头，以该行单元格数目为最大数目                    if (curRow == 1) {                        maxRef = ref;                    }                    //补全一行尾部可能缺失的单元格                    if (maxRef != null) {                        int len = -1;                        //前一单元格，true则不是文本空字符串，false则是文本空字符串                        if (charactersFlag) {                            len = countNullCell(maxRef, ref);                        } else {                            len = countNullCell(maxRef, preRef);                        }                        for (int i = 0; i <= len; i++) {                            cellList.add(curCol, "");                            curCol++;                        }                    }                    if (flag && curRow == 1) {                        columnList = (cellList);                    }                    if (flag && curRow != 1) { //该行不为空行且该行不是第一行，则发送（第一行为列名，不需要）                        cellLists.add(cellList);                        totalRows++;                        if (totalRows != 0 && totalRows % 500 == 0) {                                           cellLists.clear();                        }                        //ExcelReaderUtil.sendRows(filePath, sheetName, sheetIndex, curRow, cellList);                    }                    cellList = new ArrayList<>();                    curRow++;                    curCol = 0;                    preRef = null;                    ref = null;                    flag = false;                }            }        } catch (Exception ex) {            logger.error(ex.getMessage(), ex);        }    }    /**     * 处理数据类型     *     * @param attributes     */    public void setNextDataType(Attributes attributes) {        nextDataType = CellDataType.NUMBER; //cellType为空，则表示该单元格类型为数字        formatIndex = -1;        formatString = null;        String cellType = attributes.getValue("t"); //单元格类型        String cellStyleStr = attributes.getValue("s"); //        String columnData = attributes.getValue("r"); //获取单元格的位置，如A1,B1        if ("b".equals(cellType)) { //处理布尔值            nextDataType = CellDataType.BOOL;        } else if ("e".equals(cellType)) {  //处理错误            nextDataType = CellDataType.ERROR;        } else if ("inlineStr".equals(cellType)) {            nextDataType = CellDataType.INLINESTR;        } else if ("s".equals(cellType)) { //处理字符串            nextDataType = CellDataType.SSTINDEX;        } else if ("str".equals(cellType)) {            nextDataType = CellDataType.FORMULA;        }        if (cellStyleStr != null) { //处理日期            int styleIndex = Integer.parseInt(cellStyleStr);            XSSFCellStyle style = stylesTable.getStyleAt(styleIndex);            formatIndex = style.getDataFormat();            formatString = style.getDataFormatString();            if (formatString.contains("m/d/yyyy") || formatString.contains("yyyy/mm/dd") || formatString.contains(                    "yyyy/m/d")||formatString.contains("m/d/yy")) {                nextDataType = CellDataType.DATE;                formatString = "yyyy-MM-dd hh:mm:ss";            }            if (formatString == null) {                nextDataType = CellDataType.NULL;                formatString = BuiltinFormats.getBuiltinFormat(formatIndex);            }        }    }    /**     * 对解析出来的数据进行类型处理     *     * @param value   单元格的值，     *                value代表解析：BOOL的为0或1， ERROR的为内容值，FORMULA的为内容值，INLINESTR的为索引值需转换为内容值，     *                SSTINDEX的为索引值需转换为内容值， NUMBER为内容值，DATE为内容值     * @param thisStr 一个空字符串     * @return     */    @SuppressWarnings("deprecation")    public String getDataValue(String value, String thisStr) {        switch (nextDataType) {            // 这几个的顺序不能随便交换，交换了很可能会导致数据错误            case BOOL: //布尔值                char first = value.charAt(0);                thisStr = first == '0' ? "FALSE" : "TRUE";                break;            case ERROR: //错误                thisStr = "\"ERROR:" + value.toString() + '"';                break;            case FORMULA: //公式                thisStr = '"' + value.toString() + '"';                break;            case INLINESTR:                XSSFRichTextString rtsi = new XSSFRichTextString(value.toString());                thisStr = rtsi.toString();                rtsi = null;                break;            case SSTINDEX: //字符串                String sstIndex = value.toString();                try {                    int idx = Integer.parseInt(sstIndex);                    XSSFRichTextString rtss = new XSSFRichTextString(sst.getEntryAt(idx));//根据idx索引值获取内容值                    thisStr = rtss.toString();                    //System.out.println(thisStr);                    //有些字符串是文本格式的，但内容却是日期                    rtss = null;                } catch (NumberFormatException ex) {                    thisStr = value.toString();                }                break;            case NUMBER: //数字                if (formatString != null) {                    if(formatString.contains("reserved")){                        thisStr = formatter.formatRawCellContents(Double.parseDouble(value), formatIndex, "yyyy-MM-dd hh:mm:ss");                    }else{                        thisStr =                                formatter.formatRawCellContents(Double.parseDouble(value), formatIndex, formatString).trim();                    }                } else {                    thisStr = getRealStringValueOfDouble(Double.parseDouble(value));                }                thisStr = thisStr.replace("_", "").trim();                break;            case DATE: //日期                thisStr = formatter.formatRawCellContents(Double.parseDouble(value), formatIndex, formatString);                // 对日期字符串作特殊处理，去掉T                thisStr = thisStr.replace("T", " ");                break;            default:                thisStr = " ";                break;        }        return thisStr;    }    public int countNullCell(String ref, String preRef) {        //excel2007最大行数是1048576，最大列数是16384，最后一列列名是XFD        String xfd = ref.replaceAll("\\d+", "");        String xfd_1 = preRef.replaceAll("\\d+", "");        xfd = fillChar(xfd, 3, '@', true);        xfd_1 = fillChar(xfd_1, 3, '@', true);        char[] letter = xfd.toCharArray();        char[] letter_1 = xfd_1.toCharArray();        int res = (letter[0] - letter_1[0]) * 26 * 26 + (letter[1] - letter_1[1]) * 26 + (letter[2] - letter_1[2]);        return res - 1;    }    public String fillChar(String str, int len, char let, boolean isPre) {        int len_1 = str.length();        if (len_1 < len) {            if (isPre) {                for (int i = 0; i < (len - len_1); i++) {                    str = let + str;                }            } else {                for (int i = 0; i < (len - len_1); i++) {                    str = str + let;                }            }        }        return str;    }    /**     * @return the exceptionMessage     */    public String getExceptionMessage() {        return exceptionMessage;    }    private static String getRealStringValueOfDouble(Double d) {        String doubleStr = d.toString();        boolean b = doubleStr.contains("E");        int indexOfPoint = doubleStr.indexOf('.');        if (b) {            int indexOfE = doubleStr.indexOf('E');            BigInteger xs = new BigInteger(doubleStr.substring(indexOfPoint                    + BigInteger.ONE.intValue(), indexOfE));            int pow = Integer.valueOf(doubleStr.substring(indexOfE                    + BigInteger.ONE.intValue()));            int xsLen = xs.toByteArray().length;            int scale = xsLen - pow > 0 ? xsLen - pow : 0;            doubleStr = String.format("%." + scale + "f", d);        } else {            java.util.regex.Pattern p = Pattern.compile(".0$");            java.util.regex.Matcher m = p.matcher(doubleStr);            if (m.find()) {                doubleStr = doubleStr.replace(".0", "");            }        }        return doubleStr;    }}
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以上代码需引用common.io架包

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