import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; import java.io.InputStream; import java.util.Date; import java.util.HashMap; import java.util.Map; import org.apache.poi.hssf.usermodel.HSSFWorkbook; import org.apache.poi.ss.usermodel.Cell; import org.apache.poi.ss.usermodel.DateUtil; 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.slf4j.Logger; import org.slf4j.LoggerFactory; /** * 读取Excel * * @author zengwendong */ public class ReadExcelUtils { private Logger logger = LoggerFactory.getLogger(ReadExcelUtils.class); private Workbook wb; private Sheet sheet; private Row row; public ReadExcelUtils(String filepath) { if(filepath==null){ return; } String ext = filepath.substring(filepath.lastIndexOf(".")); try { InputStream is = new FileInputStream(filepath); if(".xls".equals(ext)){ wb = new HSSFWorkbook(is); }else if(".xlsx".equals(ext)){ wb = new XSSFWorkbook(is); }else{ wb=null; } } catch (FileNotFoundException e) { logger.error("FileNotFoundException", e); } catch (IOException e) { logger.error("IOException", e); } } /** * 读取Excel表格表头的内容 * * @param InputStream * @return String 表头内容的数组 * @author zengwendong */ public String[] readExcelTitle() throws Exception{ if(wb==null){ throw new Exception("Workbook对象为空!"); } sheet = wb.getSheetAt(0); row = sheet.getRow(0); // 标题总列数 int colNum = row.getPhysicalNumberOfCells(); System.out.println("colNum:" + colNum); String[] title = new String[colNum]; for (int i = 0; i < colNum; i++) { // title[i] = getStringCellValue(row.getCell((short) i)); title[i] = row.getCell(i).getCellFormula(); } return title; } /** * 读取Excel数据内容 * * @param InputStream * @return Map 包含单元格数据内容的Map对象 * @author zengwendong */ public Map<Integer, Map<Integer,Object>> readExcelContent() throws Exception{ if(wb==null){ throw new Exception("Workbook对象为空!"); } Map<Integer, Map<Integer,Object>> content = new HashMap<Integer, Map<Integer,Object>>(); sheet = wb.getSheetAt(0); // 得到总行数 int rowNum = sheet.getLastRowNum(); row = sheet.getRow(0); int colNum = row.getPhysicalNumberOfCells(); // 正文内容应该从第二行开始,第一行为表头的标题 for (int i = 1; i <= rowNum; i++) { row = sheet.getRow(i); int j = 0; Map<Integer,Object> cellValue = new HashMap<Integer, Object>(); while (j < colNum) { Object obj = getCellFormatValue(row.getCell(j)); cellValue.put(j, obj); j++; } content.put(i, cellValue); } return content; } /** * * 根据Cell类型设置数据 * * @param cell * @return * @author zengwendong */ private Object getCellFormatValue(Cell cell) { Object cellvalue = ""; if (cell != null) { // 判断当前Cell的Type switch (cell.getCellType()) { case Cell.CELL_TYPE_NUMERIC:// 如果当前Cell的Type为NUMERIC case Cell.CELL_TYPE_FORMULA: { // 判断当前的cell是否为Date if (DateUtil.isCellDateFormatted(cell)) { // 如果是Date类型则,转化为Data格式 // data格式是带时分秒的:2013-7-10 0:00:00 // cellvalue = cell.getDateCellValue().toLocaleString(); // data格式是不带带时分秒的:2013-7-10 Date date = cell.getDateCellValue(); cellvalue = date; } else {// 如果是纯数字 // 取得当前Cell的数值 cellvalue = String.valueOf(cell.getNumericCellValue()); } break; } case Cell.CELL_TYPE_STRING:// 如果当前Cell的Type为STRING // 取得当前的Cell字符串 cellvalue = cell.getRichStringCellValue().getString(); break; default:// 默认的Cell值 cellvalue = ""; } } else { cellvalue = ""; } return cellvalue; } public static void main(String[] args) { try { String filepath = "F:test.xls"; ReadExcelUtils excelReader = new ReadExcelUtils(filepath); // 对读取Excel表格标题测试 // String[] title = excelReader.readExcelTitle(); // System.out.println("获得Excel表格的标题:"); // for (String s : title) { // System.out.print(s + " "); // } // 对读取Excel表格内容测试 Map<Integer, Map<Integer,Object>> map = excelReader.readExcelContent(); System.out.println("获得Excel表格的内容:"); for (int i = 1; i <= map.size(); i++) { System.out.println(map.get(i)); } } catch (FileNotFoundException e) { System.out.println("未找到指定路径的文件!"); e.printStackTrace(); }catch (Exception e) { e.printStackTrace(); } } }

Java'splatformindependencemeansdeveloperscanwritecodeonceandrunitonanydevicewithoutrecompiling.ThisisachievedthroughtheJavaVirtualMachine(JVM),whichtranslatesbytecodeintomachine-specificinstructions,allowinguniversalcompatibilityacrossplatforms.Howev

To set up the JVM, you need to follow the following steps: 1) Download and install the JDK, 2) Set environment variables, 3) Verify the installation, 4) Set the IDE, 5) Test the runner program. Setting up a JVM is not just about making it work, it also involves optimizing memory allocation, garbage collection, performance tuning, and error handling to ensure optimal operation.

ToensureJavaplatformindependence,followthesesteps:1)CompileandrunyourapplicationonmultipleplatformsusingdifferentOSandJVMversions.2)UtilizeCI/CDpipelineslikeJenkinsorGitHubActionsforautomatedcross-platformtesting.3)Usecross-platformtestingframeworkss

Javastandsoutinmoderndevelopmentduetoitsrobustfeatureslikelambdaexpressions,streams,andenhancedconcurrencysupport.1)Lambdaexpressionssimplifyfunctionalprogramming,makingcodemoreconciseandreadable.2)Streamsenableefficientdataprocessingwithoperationsli

The core features of Java include platform independence, object-oriented design and a rich standard library. 1) Object-oriented design makes the code more flexible and maintainable through polymorphic features. 2) The garbage collection mechanism liberates the memory management burden of developers, but it needs to be optimized to avoid performance problems. 3) The standard library provides powerful tools from collections to networks, but data structures should be selected carefully to keep the code concise.

Yes,Javacanruneverywhereduetoits"WriteOnce,RunAnywhere"philosophy.1)Javacodeiscompiledintoplatform-independentbytecode.2)TheJavaVirtualMachine(JVM)interpretsorcompilesthisbytecodeintomachine-specificinstructionsatruntime,allowingthesameJava

JDKincludestoolsfordevelopingandcompilingJavacode,whileJVMrunsthecompiledbytecode.1)JDKcontainsJRE,compiler,andutilities.2)JVMmanagesbytecodeexecutionandsupports"writeonce,runanywhere."3)UseJDKfordevelopmentandJREforrunningapplications.

Key features of Java include: 1) object-oriented design, 2) platform independence, 3) garbage collection mechanism, 4) rich libraries and frameworks, 5) concurrency support, 6) exception handling, 7) continuous evolution. These features of Java make it a powerful tool for developing efficient and maintainable software.


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