Read Huge Excel file(500K rows) in java

Question

I am trying to read a Big XLSX File. The Excel file has around 500K rows.I need to read col 2.

OPCPackage pkg;
pkg = OPCPackage.open("File path");
XSSFWorkbook myWorkBook = new XSSFWorkbook(pkg);
Sheet sheet = myWorkBook.getSheetAt(2);
Iterator<Row> rowIterator = sheet.iterator();
while (rowIterator.hasNext())
{
Row row = rowIterator.next();
if (row_num > ROW_ESCAPE) 
{
   Cell cell = row.getCell(2);
  if (!cell.getStringCellValue().toString().trim().isEmpty()) 
            {
                System.out.println(cell.getStringCellValue().toString());
            }
System.out.println("hi"+row_num);
        }
        row_num++;
 }

It prints till row 39723 After that it throws the below exception

Exception in thread "AWT-EventQueue-0" java.lang.OutOfMemoryError: Java heap space
at java.util.regex.Matcher.<init>(Matcher.java:225)
at java.util.regex.Pattern.matcher(Pattern.java:1093)
at org.apache.poi.xssf.usermodel.XSSFRichTextString.utfDecode(XSSFRichTextString.java:482)
at org.apache.poi.xssf.usermodel.XSSFRichTextString.getString(XSSFRichTextString.java:297)
at org.apache.poi.xssf.usermodel.XSSFCell.getStringCellValue(XSSFCell.java:262)
at Main.get_titles(Main.java:484)
at Main.analyze_Importsheet(Main.java:461)
at Main.but_sel_imp_sheetActionPerformed(Main.java:220)
at Main.access$000(Main.java:40)
at Main$1.actionPerformed(Main.java:85)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6533)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
at java.awt.Component.processEvent(Component.java:6298)
at java.awt.Container.processEvent(Container.java:2236)
at java.awt.Component.dispatchEventImpl(Component.java:4889)
at java.awt.Container.dispatchEventImpl(Container.java:2294)
at java.awt.Component.dispatchEvent(Component.java:4711)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466)
at java.awt.Container.dispatchEventImpl(Container.java:2280)
at java.awt.Window.dispatchEventImpl(Window.java:2746)
at java.awt.Component.dispatchEvent(Component.java:4711)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:709)
at java.awt.EventQueue$3.run(EventQueue.java:703)

Main.java:484=if (!cell.getStringCellValue().toString().trim().isEmpty()) If i remove that line and just print the row number, it works fine. I need help how to get the string value for col 2.

Answer 1

Use the streaming eventmodel API, not the in-memory usermodel API.

See Apache POI: How to use the HSSF Event API.