[github-290] Customize Spliterator implementations for better parallelism. Thanks to Daniel Shuy. This closes #290

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1896305 13f79535-47bb-0310-9956-ffa450edef68

poi-ooxml/src/main/java/org/apache/poi/openxml4j/opc/PackageRelationshipCollection.java

         return relationshipsByID.values().iterator();
     }
 
+    /**
+     * Get this collection's spliterator.
+     *
+     * @since POI 5.2.0
+     */
+    @Override
+    public Spliterator<PackageRelationship> spliterator() {
+        return relationshipsByID.values().spliterator();
+    }
+
     /**
      * Get an iterator of a collection with all relationship with the specified
      * type.

poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/text/XDDFTextParagraph.java

 import java.util.Iterator;
 import java.util.List;
 import java.util.Optional;
+import java.util.Spliterator;
 import java.util.function.Function;
 import java.util.function.Predicate;
 
  * is the highest level text separation mechanism.
  */
 @Beta
-public class XDDFTextParagraph {
+public class XDDFTextParagraph implements Iterable<XDDFTextRun> {
     private XDDFTextBody _parent;
     private XDDFParagraphProperties _properties;
     private final CTTextParagraph _p;
         return _runs;
     }
 
+    @Override
     public Iterator<XDDFTextRun> iterator() {
         return _runs.iterator();
     }
 
+    /**
+     * @since POI 5.2.0
+     */
+    @Override
+    public Spliterator<XDDFTextRun> spliterator() {
+        return _runs.spliterator();
+    }
+
     /**
      * Append a line break.
      *

poi-ooxml/src/main/java/org/apache/poi/xslf/usermodel/XSLFTextShape.java

 import java.util.Iterator;
 import java.util.List;
 import java.util.Optional;
+import java.util.Spliterator;
 import java.util.function.Function;
 import java.util.function.Predicate;
 
         return getTextParagraphs().iterator();
     }
 
+    /**
+     * @since POI 5.2.0
+     */
+    @Override
+    public Spliterator<XSLFTextParagraph> spliterator() {
+        return getTextParagraphs().spliterator();
+    }
+
     @Override
     public String getText() {
         StringBuilder out = new StringBuilder();

poi-ooxml/src/main/java/org/apache/poi/xssf/streaming/SXSSFDrawing.java

 package org.apache.poi.xssf.streaming;
 
 import java.util.Iterator;
+import java.util.Spliterator;
 
 import org.apache.poi.ss.usermodel.ClientAnchor;
 import org.apache.poi.ss.usermodel.Comment;
     public Iterator<XSSFShape> iterator() {
         return _drawing.getShapes().iterator();
     }
-    
+
+    /**
+     * @since POI 5.2.0
+     */
+    @Override
+    public Spliterator<XSSFShape> spliterator() {
+        return _drawing.getShapes().spliterator();
+    }
+
 }
 

poi-ooxml/src/main/java/org/apache/poi/xssf/streaming/SXSSFRow.java

 import java.util.Map.Entry;
 import java.util.NoSuchElementException;
 import java.util.SortedMap;
+import java.util.Spliterator;
+import java.util.Spliterators;
 import java.util.TreeMap;
 
 import org.apache.poi.ss.SpreadsheetVersion;
         return new CellIterator();
     }
 
+    public Spliterator<Cell> allCellsSpliterator()
+    {
+        return Spliterators.spliterator(allCellsIterator(), getLastCellNum(), 0);
+    }
+
     public boolean hasCustomHeight()
     {
         return _height!=-1;
         this._collapsed = collapsed;
     }
 //begin of interface implementation
-    /**
-     * {@inheritDoc}
-     */
-    @Override
-    public Iterator<Cell> iterator()
-    {
-        return new FilledCellIterator();
-    }
-
     /**
      * Use this to create new cells within the row and return it.
      * <p>
     @Override
     public Iterator<Cell> cellIterator()
     {
-        return iterator();
+        return new FilledCellIterator();
+    }
+
+    /**
+     * Create a spliterator over the cells from [0, getLastCellNum()).
+     * Includes blank cells, excludes empty cells
+     *
+     * Returns a spliterator over all filled cells (created via Row.createCell())
+     * Throws ConcurrentModificationException if cells are added, moved, or
+     * removed after the spliterator is created.
+     *
+     * @since POI 5.2.0
+     */
+    @Override
+    @SuppressWarnings("unchecked")
+    public Spliterator<Cell> spliterator() {
+        return (Spliterator<Cell>)(Spliterator<? extends Cell>) _cells.values().spliterator();
     }
 
     /**

poi-ooxml/src/main/java/org/apache/poi/xssf/streaming/SXSSFSheet.java

 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.Spliterator;
 import java.util.TreeMap;
 
 import org.apache.poi.ss.SpreadsheetVersion;
     }
 
     //start of interface implementation
-    @Override
-    public Iterator<Row> iterator() {
-        return rowIterator();
-    }
-
     /**
      * Create a new row within the sheet and return the high level representation
      *
         return result;
     }
 
+    /**
+     *  Returns a spliterator of the physical rows
+     *
+     * @return a spliterator of the PHYSICAL rows.  Meaning the 3rd element may not
+     * be the third row if say for instance the second row is undefined.
+     *
+     * @since POI 5.2.0
+     */
+    @Override
+    @SuppressWarnings("unchecked")
+    public Spliterator<Row> spliterator() {
+        return (Spliterator<Row>)(Spliterator<? extends Row>) _rows.values().spliterator();
+    }
+
     /**
      * Flag indicating whether the sheet displays Automatic Page Breaks.
      *

poi-ooxml/src/main/java/org/apache/poi/xssf/streaming/SXSSFWorkbook.java

 import java.util.List;
 import java.util.Map;
 import java.util.NoSuchElementException;
+import java.util.Spliterator;
 
 import org.apache.commons.compress.archivers.ArchiveOutputStream;
 import org.apache.commons.compress.archivers.zip.Zip64Mode;
         return new SheetIterator<>();
     }
 
+    /**
+     *  Returns a spliterator of the sheets in the workbook
+     *  in sheet order. Includes hidden and very hidden sheets.
+     *
+     * @return a spliterator of the sheets.
+     *
+     * @since POI 5.2.0
+     */
+    @Override
+    public Spliterator<Sheet> spliterator() {
+        return _wb.spliterator();
+    }
+
     protected final class SheetIterator<T extends Sheet> implements Iterator<T> {
         final private Iterator<XSSFSheet> it;
         @SuppressWarnings("unchecked")
         }
     }
 
-    /**
-     * Alias for {@link #sheetIterator()} to allow
-     * foreach loops
-     */
-    @Override
-    public Iterator<Sheet> iterator() {
-        return sheetIterator();
-    }
-
     /**
      * Get the Sheet object at the given index.
      *

poi-ooxml/src/main/java/org/apache/poi/xssf/usermodel/XSSFDrawing.java

 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Spliterator;
 
 import javax.xml.namespace.QName;
 
         return getShapes().iterator();
     }
 
+    /**
+     * @since POI 5.2.0
+     */
+    @Override
+    public Spliterator<XSSFShape> spliterator() {
+        return getShapes().spliterator();
+    }
+
     /**
      * @return the sheet associated with the drawing
      */

poi-ooxml/src/main/java/org/apache/poi/xssf/usermodel/XSSFRow.java

 import java.util.Iterator;
 import java.util.Objects;
 import java.util.Set;
+import java.util.Spliterator;
 import java.util.TreeMap;
 
 import org.apache.poi.ss.SpreadsheetVersion;
     }
 
     /**
-     * Alias for {@link #cellIterator()} to allow  foreach loops:
-     * <blockquote><pre>
-     * for(Cell cell : row){
-     *     ...
-     * }
-     * </pre></blockquote>
+     * Cell spliterator over the physically defined cells
      *
-     * @return an iterator over cells in this row.
+     * @return a spliterator over cells in this row.
+     *
+     * @since POI 5.2.0
      */
     @Override
-    public Iterator<Cell> iterator() {
-        return cellIterator();
+    @SuppressWarnings("unchecked")
+    public Spliterator<Cell> spliterator() {
+        return (Spliterator<Cell>)(Spliterator<? extends Cell>)_cells.values().spliterator();
     }
 
     /**

poi-ooxml/src/main/java/org/apache/poi/xssf/usermodel/XSSFShapeGroup.java

 package org.apache.poi.xssf.usermodel;
 
 import java.util.Iterator;
+import java.util.Spliterator;
 
 import org.apache.poi.openxml4j.opc.PackageRelationship;
 import org.apache.poi.ss.usermodel.ShapeContainer;
         return getDrawing().getShapes(this).iterator();
     }
 
+    /**
+     * @since POI 5.2.0
+     */
+    @Override
+    public Spliterator<XSSFShape> spliterator() {
+        return getDrawing().getShapes(this).spliterator();
+    }
+
     @Override
     public String getShapeName() {
         return ctGroup.getNvGrpSpPr().getCNvPr().getName();

poi-ooxml/src/main/java/org/apache/poi/xssf/usermodel/XSSFSheet.java

     }
 
     /**
-     * Alias for {@link #rowIterator()} to
-     *  allow foreach loops
+     * @return a spliterator of the PHYSICAL rows.  Meaning the 3rd element may not
+     * be the third row if say for instance the second row is undefined.
+     * Call getRowNum() on each row if you care which one it is.
+     *
+     * @since POI 5.2.0
      */
     @Override
-    public Iterator<Row> iterator() {
-        return rowIterator();
+    @SuppressWarnings("unchecked")
+    public Spliterator<Row> spliterator() {
+        return (Spliterator<Row>)(Spliterator<? extends Row>) _rows.values().spliterator();
     }
 
     /**

poi-ooxml/src/main/java/org/apache/poi/xssf/usermodel/XSSFSimpleShape.java

 import java.util.List;
 import java.util.Locale;
 import java.util.Optional;
+import java.util.Spliterator;
 import java.util.function.Function;
 import java.util.function.Predicate;
 
         return _paragraphs.iterator();
     }
 
+    /**
+     * @since POI 5.2.0
+     */
+    @Override
+    public Spliterator<XSSFTextParagraph> spliterator() {
+        return _paragraphs.spliterator();
+    }
+
     /**
      * Returns the text from all paragraphs in the shape. Paragraphs are
      * separated by new lines.

poi-ooxml/src/main/java/org/apache/poi/xssf/usermodel/XSSFWorkbook.java

 import java.util.Locale;
 import java.util.Map;
 import java.util.NoSuchElementException;
+import java.util.Spliterator;
 import java.util.regex.Pattern;
 
 import javax.xml.namespace.QName;
         return sheetIterator();
     }
 
+    /**
+     * Returns a spliterator of the sheets in the workbook
+     * in sheet order. Includes hidden and very hidden sheets.
+     *
+     * @return a spliterator of the sheets.
+     *
+     * @since POI 5.2.0
+     */
+    @Override
+    @SuppressWarnings("unchecked")
+    public Spliterator<Sheet> spliterator() {
+        return (Spliterator<Sheet>)(Spliterator<? extends Sheet>) sheets.spliterator();
+    }
+
     private final class SheetIterator<T extends Sheet> implements Iterator<T> {
         final private Iterator<T> it;
         @SuppressWarnings("unchecked")

poi-ooxml/src/main/java/org/apache/poi/xwpf/usermodel/XWPFAbstractFootnoteEndnote.java

 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Spliterator;
 
 import org.apache.poi.ooxml.POIXMLDocumentPart;
 import org.apache.poi.util.Internal;
         return paragraphs.iterator();
     }
 
+    /**
+     * Get a spliterator over the {@link XWPFParagraph}s in the footnote.
+     * @return Spliterator over the paragraph list.
+     *
+     * @since POI 5.2.0
+     */
+    @Override
+    public Spliterator<XWPFParagraph> spliterator() {
+        return paragraphs.spliterator();
+    }
+
     /**
      * Get the list of {@link XWPFTable}s in the footnote.
      * @return List of tables

poi-ooxml/src/main/java/org/apache/poi/xwpf/usermodel/XWPFDocument.java

 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
+import java.util.Spliterator;
 
 import javax.xml.namespace.QName;
 
         return bodyElements.iterator();
     }
 
+    /**
+     * returns a Spliterator with paragraphs and tables
+     *
+     * @since POI 5.2.0
+     */
+    public Spliterator<IBodyElement> getBodyElementsSpliterator() {
+        return bodyElements.spliterator();
+    }
+
     @Override
     public List<XWPFParagraph> getParagraphs() {
         return Collections.unmodifiableList(paragraphs);
         return tables.iterator();
     }
 
+    /**
+     * @since POI 5.2.0
+     */
+    public Spliterator<XWPFTable> getTablesSpliterator() {
+        return tables.spliterator();
+    }
+
     public Iterator<XWPFParagraph> getParagraphsIterator() {
         return paragraphs.iterator();
     }
 
+    /**
+     * @since POI 5.2.0
+     */
+    public Spliterator<XWPFParagraph> getParagraphsSpliterator() {
+        return paragraphs.spliterator();
+    }
+
     /**
      * Returns the paragraph that of position pos
      */

poi-ooxml/src/test/java/org/apache/poi/xssf/streaming/TestSXSSFSheet.java

         assertEquals(2, row0.getRowNum(), "Row 2 knows its row number");
         assertEquals(1, sheet.getRowNum(row1), "Sheet knows Row 1's row number");
         assertEquals(2, sheet.getRowNum(row0), "Sheet knows Row 2's row number");
-        assertEquals(row1, sheet.iterator().next(), "Sheet row iteratation order should be ascending");
+        assertEquals(row1, sheet.iterator().next(), "Sheet row iteration order should be ascending");
+        sheet.spliterator().tryAdvance(row ->
+                assertEquals(row1, row, "Sheet row iteration order should be ascending"));
 
         wb.close();
     }

poi-scratchpad/src/main/java/org/apache/poi/hslf/record/PPDrawing.java

 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
+import java.util.Spliterator;
 import java.util.function.Function;
 import java.util.function.Predicate;
 import java.util.function.Supplier;
         return getEscherRecords().iterator();
     }
 
+    /**
+     * @since POI 5.2.0
+     */
+    @Override
+    public Spliterator<EscherRecord> spliterator() {
+        return getEscherRecords().spliterator();
+    }
+
     /**
      * Get access to the atoms inside Textboxes
      */

poi-scratchpad/src/main/java/org/apache/poi/hslf/usermodel/HSLFGroupShape.java

 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Spliterator;
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
         return getShapes().iterator();
     }
 
+    /**
+     * @since POI 5.2.0
+     */
+    @Override
+    public Spliterator<HSLFShape> spliterator() {
+        return getShapes().spliterator();
+    }
+
     @Override
     public boolean removeShape(HSLFShape shape) {
         // TODO: implement!

poi-scratchpad/src/main/java/org/apache/poi/hslf/usermodel/HSLFSheet.java

 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Spliterator;
 
 import org.apache.poi.ddf.EscherContainerRecord;
 import org.apache.poi.ddf.EscherDgRecord;
         return getShapes().iterator();
     }
 
+    /**
+     * @since POI 5.2.0
+     */
+    @Override
+    public Spliterator<HSLFShape> spliterator() {
+        return getShapes().spliterator();
+    }
 
     /**
      * @return whether shapes on the master sheet should be shown. By default master graphics is turned off.

poi-scratchpad/src/main/java/org/apache/poi/hslf/usermodel/HSLFTextParagraph.java

 import java.util.Arrays;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Spliterator;
 import java.util.function.Consumer;
 import java.util.stream.Collectors;
 
         return _runs.iterator();
     }
 
+    /**
+     * @since POI 5.2.0
+     */
+    @Override
+    public Spliterator<HSLFTextRun> spliterator() {
+        return _runs.spliterator();
+    }
+
     @Override
     public Double getLeftMargin() {
         Integer val = null;

poi-scratchpad/src/main/java/org/apache/poi/hslf/usermodel/HSLFTextShape.java

 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Spliterator;
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
         return _paragraphs.iterator();
     }
 
+    /**
+     * @since POI 5.2.0
+     */
+    @Override
+    public Spliterator<HSLFTextParagraph> spliterator() {
+        return _paragraphs.spliterator();
+    }
+
     @Override
     public Insets2D getInsets() {
         return new Insets2D(getTopInset(), getLeftInset(), getBottomInset(), getRightInset());

poi/src/main/java/org/apache/poi/ddf/EscherArrayProperty.java

 import java.util.Iterator;
 import java.util.Map;
 import java.util.NoSuchElementException;
+import java.util.Spliterator;
+import java.util.Spliterators;
 import java.util.function.Supplier;
 import java.util.stream.Collectors;
 import java.util.stream.StreamSupport;
         };
     }
 
+    /**
+     * @since POI 5.2.0
+     */
+    @Override
+    public Spliterator<byte[]> spliterator() {
+        return Spliterators.spliterator(iterator(), getNumberOfElementsInArray(), 0);
+    }
+
     @Override
     public Map<String, Supplier<?>> getGenericProperties() {
         return GenericRecordUtil.getGenericProperties(

poi/src/main/java/org/apache/poi/ddf/EscherContainerRecord.java

 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
+import java.util.Spliterator;
 import java.util.function.Supplier;
 
 import org.apache.logging.log4j.LogManager;
         return Collections.unmodifiableList(_childRecords).iterator();
     }
 
+    /**
+     * @return a spliterator over the child records
+     *
+     * @since POI 5.2.0
+     */
+    @Override
+    public Spliterator<EscherRecord> spliterator() {
+        return _childRecords.spliterator();
+    }
 
     /**
      * replaces the internal child list with the contents of the supplied {@code childRecords}

poi/src/main/java/org/apache/poi/hssf/record/PageBreakRecord.java

 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.Map;
+import java.util.Spliterator;
 import java.util.function.Supplier;
 
 import org.apache.poi.common.usermodel.GenericRecord;
         return _breaks.iterator();
     }
 
+    /**
+     * @since POI 5.2.0
+     */
+    public final Spliterator<Break> getBreaksSpliterator() {
+        return _breaks.spliterator();
+    }
+
    /**
     * Adds the page break at the specified parameters
     * @param main Depending on sid, will determine row or column to put page break (zero-based)

poi/src/main/java/org/apache/poi/hssf/record/aggregates/RowRecordsAggregate.java

 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
+import java.util.Spliterator;
 import java.util.TreeMap;
 
 import org.apache.poi.hssf.model.RecordStream;
         return _rowRecords.values().iterator();
     }
 
+    /**
+     * @since POI 5.2.0
+     */
+    public Spliterator<RowRecord> getSpliterator() {
+        return _rowRecords.values().spliterator();
+    }
+
     public int findStartOfRowOutlineGroup(int row) {
         // Find the start of the group.
         RowRecord rowRecord = this.getRow( row );
         return _valuesAgg.iterator();
     }
 
+    /**
+     * Returns a spliterator for the cell values
+     *
+     * @since POI 5.2.0
+     */
+    public Spliterator<CellValueRecordInterface> getCellValueSpliterator() {
+        return _valuesAgg.spliterator();
+    }
+
     public IndexRecord createIndexRecord(int indexRecordOffset, int sizeOfInitialSheetRecords) {
         IndexRecord result = new IndexRecord();
         result.setFirstRow(_firstrow);

poi/src/main/java/org/apache/poi/hssf/record/aggregates/ValueRecordsAggregate.java

 
 import java.util.Iterator;
 import java.util.NoSuchElementException;
+import java.util.Spliterator;
+import java.util.Spliterators;
 
 import org.apache.poi.hssf.model.RecordStream;
 import org.apache.poi.hssf.record.BlankRecord;
     public Iterator<CellValueRecordInterface> iterator() {
         return new ValueIterator();
     }
+
+    /**
+     * value spliterator
+     *
+     * @since POI 5.2.0
+     */
+    @Override
+    public Spliterator<CellValueRecordInterface> spliterator() {
+        return Spliterators.spliterator(iterator(), getPhysicalNumberOfCells(), 0);
+    }
 }

poi/src/main/java/org/apache/poi/hssf/record/common/UnicodeString.java

 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
+import java.util.Spliterator;
 import java.util.function.Supplier;
 import java.util.stream.Collectors;
 
       return null;
     }
 
+    /**
+     * @since POI 5.2.0
+     */
+    public Spliterator<FormatRun> formatSpliterator() {
+        if (field_4_format_runs != null) {
+            return field_4_format_runs.spliterator();
+        }
+        return null;
+    }
+
     public void removeFormatRun(FormatRun r) {
       field_4_format_runs.remove(r);
       if (field_4_format_runs.size() == 0) {

poi/src/main/java/org/apache/poi/hssf/usermodel/HSSFPatriarch.java

 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.Spliterator;
 
 import org.apache.poi.ddf.EscherComplexProperty;
 import org.apache.poi.ddf.EscherContainerRecord;
         return _shapes.iterator();
     }
 
+    /**
+     * @since POI 5.2.0
+     */
+    @Override
+    public Spliterator<HSSFShape> spliterator() {
+        return _shapes.spliterator();
+    }
+
     protected HSSFSheet getSheet() {
         return _sheet;
     }

poi/src/main/java/org/apache/poi/hssf/usermodel/HSSFRow.java

     {
       return new CellIterator();
     }
-    /**
-     * Alias for {@link #cellIterator} to allow
-     *  foreach loops
-     */
-    @Override
-    public Iterator<Cell> iterator() {
-       return cellIterator();
-    }
 
     /**
      * An iterator over the (physical) cells in the row.

poi/src/main/java/org/apache/poi/hssf/usermodel/HSSFShapeGroup.java

 import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Spliterator;
 
 import org.apache.poi.ddf.DefaultEscherRecordFactory;
 import org.apache.poi.ddf.EscherBoolProperty;
     public Iterator<HSSFShape> iterator() {
         return shapes.iterator();
     }
+
+    /**
+     * @since POI 5.2.0
+     */
+    @Override
+    public Spliterator<HSSFShape> spliterator() {
+        return shapes.spliterator();
+    }
 }

poi/src/main/java/org/apache/poi/hssf/usermodel/HSSFSheet.java

 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
+import java.util.Spliterator;
 import java.util.TreeMap;
 import java.util.TreeSet;
 
     }
 
     /**
-     * Alias for {@link #rowIterator()} to allow
-     * foreach loops
+     * @return a spliterator of the PHYSICAL rows.  Meaning the 3rd element may not
+     *         be the third row if say for instance the second row is undefined.
+     *         Call getRowNum() on each row if you care which one it is.
+     *
+     * @since POI 5.2.0
      */
     @Override
-    public Iterator<Row> iterator() {
-        return rowIterator();
+    @SuppressWarnings("unchecked") // can this clumsy generic syntax be improved?
+    public Spliterator<Row> spliterator() {
+        return (Spliterator<Row>)(Spliterator<? extends Row>) _rows.values().spliterator();
     }
 
-
     /**
      * used internally in the API to get the low level Sheet record represented by this
      * Object.

poi/src/main/java/org/apache/poi/hssf/usermodel/HSSFWorkbook.java

 import java.util.Map;
 import java.util.NoSuchElementException;
 import java.util.Set;
+import java.util.Spliterator;
 import java.util.regex.Pattern;
 
 import org.apache.commons.codec.digest.DigestUtils;
     }
 
     /**
-     * Alias for {@link #sheetIterator()} to allow
-     * foreach loops
+     * Returns a spliterator of the sheets in the workbook
+     * in sheet order. Includes hidden and very hidden sheets.
+     *
+     * @return a spliterator of the sheets.
+     *
+     * @since POI 5.2.0
      */
     @Override
-    public Iterator<Sheet> iterator() {
-        return sheetIterator();
+    @SuppressWarnings("unchecked")
+    public Spliterator<Sheet> spliterator() {
+        return (Spliterator<Sheet>)(Spliterator<? extends Sheet>) _sheets.spliterator();
     }
 
     private final class SheetIterator<T extends Sheet> implements Iterator<T> {

poi/src/main/java/org/apache/poi/poifs/filesystem/DirectoryNode.java

 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.Spliterator;
 
 import org.apache.poi.hpsf.ClassID;
 import org.apache.poi.poifs.dev.POIFSViewable;
         return getEntries();
     }
 
+    /**
+     * Returns a Spliterator over all the entries
+     *
+     * @since POI 5.2.0
+     */
+    @Override
+    public Spliterator<Entry> spliterator() {
+        return _entries.spliterator();
+    }
+
     /* **********  END  begin implementation of POIFSViewable ********** */
 }   // end public class DirectoryNode
 

poi/src/main/java/org/apache/poi/poifs/filesystem/FilteringDirectoryNode.java

 import java.util.Map;
 import java.util.NoSuchElementException;
 import java.util.Set;
+import java.util.Spliterator;
+import java.util.Spliterators;
 
 import org.apache.poi.hpsf.ClassID;
 
       return getEntries();
    }
 
+   /**
+    * @since POI 5.2.0
+    */
+   @Override
+   public Spliterator<Entry> spliterator() {
+      return Spliterators.spliterator(iterator(), getEntryCount(), 0);
+   }
+
    @Override
    public int getEntryCount() {
       int size = directory.getEntryCount();

poi/src/main/java/org/apache/poi/poifs/property/DirectoryProperty.java

 import java.util.Iterator;
 import java.util.List;
 import java.util.Set;
+import java.util.Spliterator;
 
 /**
  * Directory property
     public Iterator<Property> iterator() {
         return getChildren();
     }
+    /**
+     * Get a spliterator over the children of this Parent; all elements
+     * are instances of Property.
+     *
+     * @return Spliterator of children; may refer to an empty collection
+     *
+     * @since POI 5.2.0
+     */
+    @Override
+    public Spliterator<Property> spliterator() {
+        return _children.spliterator();
+    }
 
     /**
      * Add a new child to the collection of children

poi/src/main/java/org/apache/poi/sl/draw/geom/CustomGeometry.java

 import java.util.Iterator;
 import java.util.List;
 import java.util.Objects;
+import java.util.Spliterator;
 
 /**
  * Definition of a custom geometric shape
         return paths.iterator();
     }
 
+    /**
+     * @since POI 5.2.0
+     */
+    @Override
+    public Spliterator<PathIf> spliterator() {
+        return paths.spliterator();
+    }
+
     public Path getTextBounds(){
         return textBounds;
     }

poi/src/main/java/org/apache/poi/ss/formula/functions/LookupUtils.java

 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.Map;
+import java.util.Spliterator;
+import java.util.Spliterators;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
                 }
             };
         }
+        /**
+         * @since POI 5.2.0
+         */
+        default Spliterator<Integer> indexSpliterator() {
+            return Spliterators.spliterator(indexIterator(), getSize(), 0);
+        }
         default Iterator<Integer> reverseIndexIterator() {
             return new Iterator<Integer>() {
                 int pos = getSize() - 1;
                 }
             };
         }
+        /**
+         * @since POI 5.2.0
+         */
+        default Spliterator<Integer> reverseIndexSpliterator() {
+            return Spliterators.spliterator(reverseIndexIterator(), getSize(), 0);
+        }
     }
 
     private static final class RowVector implements ValueVector {

poi/src/main/java/org/apache/poi/ss/usermodel/Row.java

 package org.apache.poi.ss.usermodel;
 
 import java.util.Iterator;
+import java.util.Spliterator;
+import java.util.Spliterators;
 
 /**
  * High level representation of a row of a spreadsheet.
      */
     Iterator<Cell> cellIterator();
 
+    /**
+     * Alias for {@link #cellIterator()} to allow  foreach loops:
+     * <blockquote><pre>
+     * for(Cell cell : row){
+     *     ...
+     * }
+     * </pre></blockquote>
+     *
+     * @return an iterator over cells in this row.
+     */
+    @Override
+    default Iterator<Cell> iterator() {
+        return cellIterator();
+    }
+
+    /**
+     * @return Cell spliterator of the physically defined cells.  Note element 4 may
+     * actually be row cell depending on how many are defined!
+     *
+     * @since POI 5.2.0
+     */
+    @Override
+    default Spliterator<Cell> spliterator() {
+        return Spliterators.spliterator(cellIterator(), getPhysicalNumberOfCells(), 0);
+    }
+
     /**
      * Returns the Sheet this row belongs to
      *

poi/src/main/java/org/apache/poi/ss/usermodel/Sheet.java

 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
+import java.util.Spliterator;
+import java.util.Spliterators;
 
 import org.apache.poi.ss.util.CellAddress;
 import org.apache.poi.ss.util.CellRangeAddress;
      */
     Iterator<Row> rowIterator();
 
+    /**
+     * Alias for {@link #rowIterator()} to allow foreach loops
+     */
+    @Override
+    default Iterator<Row> iterator() {
+        return rowIterator();
+    }
+
+    /**
+     *  Returns a spliterator of the physical rows
+     *
+     * @return a spliterator of the PHYSICAL rows.  Meaning the 3rd element may not
+     * be the third row if say for instance the second row is undefined.
+     *
+     * @since POI 5.2.0
+     */
+    @Override
+    default Spliterator<Row> spliterator() {
+        return Spliterators.spliterator(rowIterator(), getPhysicalNumberOfRows(), 0);
+    }
+
     /**
      * Control if Excel should be asked to recalculate all formulas on this sheet
      * when the workbook is opened.

poi/src/main/java/org/apache/poi/ss/usermodel/Workbook.java

 import java.io.OutputStream;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Spliterator;
+import java.util.Spliterators;
 
 import org.apache.poi.ss.SpreadsheetVersion;
 import org.apache.poi.ss.formula.EvaluationWorkbook;
      */
     Iterator<Sheet> sheetIterator();
 
+    /**
+     * Alias for {@link #sheetIterator()} to allow foreach loops
+     */
+    @Override
+    default Iterator<Sheet> iterator() {
+        return sheetIterator();
+    }
+
+    /**
+     *  Returns a spliterator of the sheets in the workbook
+     *  in sheet order. Includes hidden and very hidden sheets.
+     *
+     * @return a spliterator of the sheets.
+     *
+     * @since POI 5.2.0
+     */
+    @Override
+    default Spliterator<Sheet> spliterator() {
+        return Spliterators.spliterator(sheetIterator(), getNumberOfSheets(), 0);
+    }
+
     /**
      * Get the number of spreadsheets in the workbook
      *

poi/src/main/java/org/apache/poi/ss/util/CellRangeAddressBase.java

 import java.util.Map;
 import java.util.NoSuchElementException;
 import java.util.Set;
+import java.util.Spliterator;
+import java.util.Spliterators;
 import java.util.function.Supplier;
 
 import org.apache.poi.common.Duplicatable;
         return new RowMajorCellAddressIterator(this);
     }
 
+    /**
+     * Returns a spliterator over the CellAddresses in this cell range in row-major order.
+     * @since POI 5.2.0
+     */
+    @Override
+    public Spliterator<CellAddress> spliterator() {
+        return Spliterators.spliterator(iterator(), getNumberOfCells(), 0);
+    }
+
     /**
      *  Iterates over the cell addresses in a cell range in row major order
      *

poi/src/main/java/org/apache/poi/ss/util/SSCellRange.java

 import java.lang.reflect.Array;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Spliterator;
 import java.util.stream.Stream;
 
 import org.apache.poi.ss.usermodel.Cell;
     public Iterator<K> iterator() {
         return Stream.of(_flattenedArray).iterator();
     }
+
+    /**
+     * @since POI 5.2.0
+     */
+    @Override
+    public Spliterator<K> spliterator() {
+        return Stream.of(_flattenedArray).spliterator();
+    }
 }

poi/src/main/java/org/apache/poi/util/IntMapper.java

 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
+import java.util.Spliterator;
 
 import org.apache.poi.common.Duplicatable;
 
  * update
  */
 
-public class IntMapper<T> implements Duplicatable {
+public class IntMapper<T> implements Duplicatable, Iterable<T> {
     private final List<T> elements;
     private final Map<T, Integer> valueKeyMap;
 
         return elements.iterator();
     }
 
+    /**
+     * @since POI 5.2.0
+     */
+    public Spliterator<T> spliterator() {
+        return elements.spliterator();
+    }
+
     @Override
     public IntMapper<T> copy() {
         return new IntMapper<>(this);

poi/src/test/java/org/apache/poi/hssf/model/TestDrawingShapes.java

 import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertSame;
 import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.jupiter.api.Assertions.fail;
 
 import java.io.IOException;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Spliterator;
 
 import org.apache.poi.ddf.EscherBoolProperty;
 import org.apache.poi.ddf.EscherContainerRecord;
             assertEquals(s1, iter.next());
             assertEquals(s2, iter.next());
             assertFalse(iter.hasNext());
+
+            Spliterator<HSSFShape> spliter = patriarch.spliterator();
+            spliter.tryAdvance(s -> assertEquals(s1, s));
+            spliter.tryAdvance(s -> assertEquals(s2, s));
+            assertFalse(spliter.tryAdvance(s -> fail()));
         }
     }
 

poi/src/test/java/org/apache/poi/poifs/filesystem/TestDirectoryNode.java

             }
             assertEquals(0, count);
 
+            // verify that spliterator behaves correctly
+            assertEquals(0, node.spliterator().getExactSizeIfKnown());
+
             // verify behavior of isEmpty
             assertTrue(node.isEmpty());
 
             }
             assertEquals(2, count);
 
+            // verify that spliterator behaves correctly
+            assertEquals(2, node.spliterator().getExactSizeIfKnown());
+
             // verify behavior of isEmpty
             assertFalse(node.isEmpty());
 

poi/src/test/java/org/apache/poi/poifs/filesystem/TestFilteringDirectoryNode.java

 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.jupiter.api.Assertions.fail;
 
 import java.io.ByteArrayInputStream;
 import java.io.FileNotFoundException;
 import java.util.Iterator;
 import java.util.List;
 import java.util.NoSuchElementException;
+import java.util.Spliterator;
 
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
         assertEquals(dirB, i.next());
         assertEquals(eRoot, i.next());
         assertThrows(NoSuchElementException.class, i::next, "Should throw NoSuchElementException when depleted");
+
+        Spliterator<Entry> s = d.spliterator();
+        s.tryAdvance(entry -> assertEquals(dirA, entry));
+        s.tryAdvance(entry -> assertEquals(dirB, entry));
+        s.tryAdvance(entry -> assertEquals(eRoot, entry));
+        assertFalse(s.tryAdvance(entry -> fail("Should be depleted")), "Should return false when depleted");
     }
 
     @Test
         assertEquals(dirB, i.next());
         assertThrows(NoSuchElementException.class, i::next, "Should throw NoSuchElementException when depleted");
 
+        Spliterator<Entry> s1 = d1.spliterator();
+        s1.tryAdvance(entry -> assertEquals(dirA, entry));
+        s1.tryAdvance(entry -> assertEquals(dirB, entry));
+        assertFalse(s1.tryAdvance(entry -> fail("Should be depleted")), "Should return false when depleted");
+
 
         // Filter more
         excl = Arrays.asList("NotThere", "AlsoNotThere", eRoot.getName(), dirA.getName());
         assertEquals(dirB, i.next());
         assertThrows(NoSuchElementException.class, i::next, "Should throw NoSuchElementException when depleted");
 
+        Spliterator<Entry> s2 = d2.spliterator();
+        s2.tryAdvance(entry -> assertEquals(dirB, entry));
+        assertFalse(s2.tryAdvance(entry -> fail("Should be depleted")), "Should return false when depleted");
+
         // Filter everything
         excl = Arrays.asList("NotThere", eRoot.getName(), dirA.getName(), dirB.getName());
         FilteringDirectoryNode d3 = new FilteringDirectoryNode(fs.getRoot(), excl);
 
         i = d3.getEntries();
         assertThrows(NoSuchElementException.class, i::next, "Should throw NoSuchElementException when depleted");
+
+        Spliterator<Entry> s3 = d3.spliterator();
+        assertFalse(s3.tryAdvance(entry -> fail("Should be depleted")), "Should return false when depleted");
     }
 
     @Test

poi/src/test/java/org/apache/poi/poifs/property/TestDirectoryProperty.java

             children.add(iter.next());
         }
         assertEquals(count, children.size());
+        assertEquals(count, _property.spliterator().getExactSizeIfKnown());
         if (count != 0)
         {
             boolean[] found = new boolean[ count ];

poi/src/test/java/org/apache/poi/sl/draw/geom/TestPresetGeometries.java

 
 import java.awt.geom.Path2D;
 import java.awt.geom.Rectangle2D;
+import java.util.stream.StreamSupport;
 
+import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
 
 class TestPresetGeometries {
                 Path2D path = p.getPath(ctx);
                 assertNotNull(path);
             }
+            StreamSupport.stream(geom.spliterator(), true)
+                    .map(p -> p.getPath(ctx))
+                    .forEach(Assertions::assertNotNull);
         }
 
         // we get the same instance on further calls

poi/src/test/java/org/apache/poi/ss/usermodel/BaseTestRow.java

 import static org.junit.jupiter.api.Assertions.assertSame;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.jupiter.api.Assertions.fail;
 
 import java.io.IOException;
 import java.util.Iterator;
+import java.util.Spliterator;
 
 import org.apache.poi.ss.ITestDataProvider;
 import org.apache.poi.ss.usermodel.Row.MissingCellPolicy;
         wb.close();
     }
 
+    /**
+     * Test adding cells to a row in various places and see if we can find them again.
+     */
+    @Test
+    void testSpliterator() throws IOException {
+        Workbook wb = _testDataProvider.createWorkbook();
+        Sheet sheet = wb.createSheet();
+        Row row = sheet.createRow(0);
+
+        // One cell at the beginning
+        Cell cell1 = row.createCell(1);
+        Spliterator<Cell> split = row.spliterator();
+        assertTrue(split.tryAdvance(cell -> assertSame(cell1, cell)));
+        assertFalse(split.tryAdvance(cell -> fail()));
+
+        // Add another cell at the end
+        Cell cell2 = row.createCell(99);
+        split = row.spliterator();
+        assertTrue(split.tryAdvance(cell -> assertSame(cell1, cell)));
+        assertTrue(split.tryAdvance(cell -> assertSame(cell2, cell)));
+
+        // Add another cell at the beginning
+        Cell cell3 = row.createCell(0);
+        split = row.spliterator();
+        assertTrue(split.tryAdvance(cell -> assertSame(cell3, cell)));
+        assertTrue(split.tryAdvance(cell -> assertSame(cell1, cell)));
+        assertTrue(split.tryAdvance(cell -> assertSame(cell2, cell)));
+
+        // Replace cell1
+        Cell cell4 = row.createCell(1);
+        split = row.spliterator();
+        assertTrue(split.tryAdvance(cell -> assertSame(cell3, cell)));
+        assertTrue(split.tryAdvance(cell -> assertSame(cell4, cell)));
+        assertTrue(split.tryAdvance(cell -> assertSame(cell2, cell)));
+        assertFalse(split.tryAdvance(cell -> fail()));
+
+        // Add another cell, specifying the cellType
+        Cell cell5 = row.createCell(2, CellType.STRING);
+        split = row.spliterator();
+        assertNotNull(cell5);
+        assertTrue(split.tryAdvance(cell -> assertSame(cell3, cell)));
+        assertTrue(split.tryAdvance(cell -> assertSame(cell4, cell)));
+        assertTrue(split.tryAdvance(cell -> assertSame(cell5, cell)));
+        assertTrue(split.tryAdvance(cell -> assertSame(cell2, cell)));
+        assertEquals(CellType.STRING, cell5.getCellType());
+        wb.close();
+    }
+
     @Test
     void testRowStyle() throws IOException {
        Workbook wb1 = _testDataProvider.createWorkbook();

poi/src/test/java/org/apache/poi/ss/usermodel/BaseTestSheet.java

 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.Set;
+import java.util.Spliterator;
 
 import org.apache.poi.common.usermodel.HyperlinkType;
 import org.apache.poi.hssf.usermodel.HSSFWorkbook;
             assertSame(row1, it.next());
             assertTrue(it.hasNext());
             assertSame(row2, it.next());
+            Spliterator<Row> split = sheet.spliterator();
+            assertTrue(split.tryAdvance(row -> assertSame(row1, row)));
+            assertTrue(split.tryAdvance(row -> assertSame(row2, row)));
             assertEquals(1, sheet.getLastRowNum());
 
             // Test row creation with non consecutive index
             Row row2_ovrewritten_ref = it2.next();
             assertSame(row2_ovrewritten, row2_ovrewritten_ref);
             assertEquals(100.0, row2_ovrewritten_ref.getCell(0).getNumericCellValue(), 0.0);
+            Spliterator<Row> split2 = sheet.spliterator();
+            assertTrue(split2.tryAdvance(row -> assertSame(row1, row)));
+            assertTrue(split2.tryAdvance(row -> {
+                assertSame(row2_ovrewritten, row);
+                assertEquals(100.0, row.getCell(0).getNumericCellValue(), 0.0);
+            }));
         }
     }
 

poi/src/test/java/org/apache/poi/ss/usermodel/BaseTestWorkbook.java

 import java.io.IOException;
 import java.util.ConcurrentModificationException;
 import java.util.Iterator;
+import java.util.Spliterator;
 
 import org.apache.poi.hssf.HSSFTestDataSamples;
 import org.apache.poi.ss.ITestDataProvider;
             wb.createSheet("Sheet2");
 
             Iterator<Sheet> it = wb.sheetIterator();
+            Spliterator<Sheet> split = wb.spliterator();
             it.next();
+            split.tryAdvance(sheet -> {});
             wb.setSheetOrder("Sheet2", 1);
 
             // Iterator order should be fixed when iterator is created
             assertThrows(ConcurrentModificationException.class, it::next);
+            // Spliterator order should be fixed when spliterator is created
+            assertThrows(ConcurrentModificationException.class, () -> split.tryAdvance(sheet -> {}));
         }
     }
 
             wb.createSheet("Sheet2");
 
             Iterator<Sheet> it = wb.sheetIterator();
+            Spliterator<Sheet> split = wb.spliterator();
+            it.next();
+            split.tryAdvance(sheet -> {});
             wb.removeSheetAt(1);
 
             // Iterator order should be fixed when iterator is created
             assertThrows(ConcurrentModificationException.class, it::next);
+            // Spliterator order should be fixed when spliterator is created
+            assertThrows(ConcurrentModificationException.class, () -> split.tryAdvance(sheet -> {}));
         }
     }
 

poi/src/test/java/org/apache/poi/ss/util/TestCellRangeAddress.java

 import java.io.IOException;
 import java.util.Iterator;
 import java.util.NoSuchElementException;
+import java.util.Spliterator;
+import java.util.stream.StreamSupport;
 
 import org.apache.commons.io.output.UnsynchronizedByteArrayOutputStream;
 import org.apache.poi.hssf.record.TestcaseRecordInputStream;
 import org.apache.poi.util.LittleEndianOutputStream;
+import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
 
 final class TestCellRangeAddress {
         assertEquals(4, count);
     }
 
+    @Test
+    void spliterator() {
+        final CellRangeAddress A1_B2 = new CellRangeAddress(0, 1, 0, 1);
+
+        // the cell address iterator iterates in row major order
+        final Spliterator<CellAddress> spliter = A1_B2.spliterator();
+        spliter.tryAdvance(addr ->
+                assertEquals(new CellAddress(0, 0), addr, "A1"));
+        spliter.tryAdvance(addr ->
+                assertEquals(new CellAddress(0, 1), addr, "B1"));
+        spliter.tryAdvance(addr ->
+                assertEquals(new CellAddress(1, 0), addr, "A2"));
+        spliter.tryAdvance(addr ->
+                assertEquals(new CellAddress(1, 1), addr, "B2"));
+        assertFalse(spliter.tryAdvance(addr -> fail()));
+
+        // stream
+        long count = StreamSupport.stream(A1_B2.spliterator(), false)
+                .peek(Assertions::assertNotNull)
+                .count();
+        assertEquals(4, count);
+    }
+
     private static void assertIntersects(CellRangeAddress regionA, CellRangeAddress regionB) {
         if (!(regionA.intersects(regionB) && regionB.intersects(regionA))) {
             final String A = regionA.formatAsString();