diff --git a/src/ooxml/testcases/org/apache/poi/xssf/SXSSFITestDataProvider.java b/src/ooxml/testcases/org/apache/poi/xssf/SXSSFITestDataProvider.java
index 39b520fd0..c6bb03c1e 100644
--- a/src/ooxml/testcases/org/apache/poi/xssf/SXSSFITestDataProvider.java
+++ b/src/ooxml/testcases/org/apache/poi/xssf/SXSSFITestDataProvider.java
@@ -24,6 +24,7 @@ import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.ArrayList;
+import java.util.List;
 
 import org.apache.poi.POIDataSamples;
 import org.apache.poi.ss.ITestDataProvider;
@@ -40,7 +41,9 @@ import org.apache.poi.xssf.usermodel.XSSFWorkbook;
 public final class SXSSFITestDataProvider implements ITestDataProvider {
     public static final SXSSFITestDataProvider instance = new SXSSFITestDataProvider();
 
-    private ArrayList<SXSSFWorkbook> instances = new ArrayList<SXSSFWorkbook>();
+    // an instance of all SXSSFWorkbooks opened by this TestDataProvider,
+    // so that the temporary files created can be disposed up by cleanup() 
+    private final List<SXSSFWorkbook> instances = new ArrayList<SXSSFWorkbook>();
 
     private SXSSFITestDataProvider() {
         // enforce singleton
diff --git a/src/ooxml/testcases/org/apache/poi/xssf/XSSFITestDataProvider.java b/src/ooxml/testcases/org/apache/poi/xssf/XSSFITestDataProvider.java
index 953b6a180..3ceac02a5 100644
--- a/src/ooxml/testcases/org/apache/poi/xssf/XSSFITestDataProvider.java
+++ b/src/ooxml/testcases/org/apache/poi/xssf/XSSFITestDataProvider.java
@@ -35,10 +35,12 @@ public final class XSSFITestDataProvider implements ITestDataProvider {
         // enforce singleton
     }
 
+    @Override
     public XSSFWorkbook openSampleWorkbook(String sampleFileName) {
         return XSSFTestDataSamples.openSampleWorkbook(sampleFileName);
     }
 
+    @Override
     public XSSFWorkbook writeOutAndReadBack(Workbook original) {
         if(!(original instanceof XSSFWorkbook)) {
             throw new IllegalArgumentException("Expected an instance of XSSFWorkbook, but had " + original.getClass());
@@ -46,22 +48,27 @@ public final class XSSFITestDataProvider implements ITestDataProvider {
         return XSSFTestDataSamples.writeOutAndReadBack((XSSFWorkbook)original);
     }
 
-    public XSSFWorkbook createWorkbook(){
+    @Override
+    public XSSFWorkbook createWorkbook() {
         return new XSSFWorkbook();
     }
     
+    @Override
     public FormulaEvaluator createFormulaEvaluator(Workbook wb) {
         return new XSSFFormulaEvaluator((XSSFWorkbook) wb);
     }
 
+    @Override
     public byte[] getTestDataFileContent(String fileName) {
         return POIDataSamples.getSpreadSheetInstance().readFile(fileName);
     }
 
+    @Override
     public SpreadsheetVersion getSpreadsheetVersion(){
         return SpreadsheetVersion.EXCEL2007;
     }
 
+    @Override
     public String getStandardFileNameExtension() {
         return "xlsx";
     }
diff --git a/src/testcases/org/apache/poi/hssf/HSSFITestDataProvider.java b/src/testcases/org/apache/poi/hssf/HSSFITestDataProvider.java
index d544b0b79..20ec0965b 100644
--- a/src/testcases/org/apache/poi/hssf/HSSFITestDataProvider.java
+++ b/src/testcases/org/apache/poi/hssf/HSSFITestDataProvider.java
@@ -37,13 +37,16 @@ public final class HSSFITestDataProvider implements ITestDataProvider {
         // enforce singleton
     }
     
+    @Override
     public HSSFWorkbook openSampleWorkbook(String sampleFileName) {
         return HSSFTestDataSamples.openSampleWorkbook(sampleFileName);
     }
+    
     public InputStream openWorkbookStream(String sampleFileName) {
         return HSSFTestDataSamples.openSampleFileStream(sampleFileName);
     }
     
+    @Override
     public HSSFWorkbook writeOutAndReadBack(Workbook original) {
         if(!(original instanceof HSSFWorkbook)) {
             throw new IllegalArgumentException("Expected an instance of HSSFWorkbook");
@@ -51,22 +54,27 @@ public final class HSSFITestDataProvider implements ITestDataProvider {
         return HSSFTestDataSamples.writeOutAndReadBack((HSSFWorkbook)original);
     }
     
+    @Override
     public HSSFWorkbook createWorkbook(){
         return new HSSFWorkbook();
     }
     
+    @Override
     public FormulaEvaluator createFormulaEvaluator(Workbook wb) {
         return new HSSFFormulaEvaluator((HSSFWorkbook) wb);
     }
 
+    @Override
     public byte[] getTestDataFileContent(String fileName) {
         return POIDataSamples.getSpreadSheetInstance().readFile(fileName);
     }
     
+    @Override
     public SpreadsheetVersion getSpreadsheetVersion(){
         return SpreadsheetVersion.EXCEL97;
     }
     
+    @Override
     public String getStandardFileNameExtension() {
         return "xls";
     }