[github-278] Resolve all SpotBugs P1 issues in Main and Test. Thanks to Andreas Reichel. This closes #278

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1895016 13f79535-47bb-0310-9956-ffa450edef68

34 files changed, 110 insertions, 104 deletions

diff --git a/poi-examples/src/main/java/org/apache/poi/examples/hssf/usermodel/AddDimensionedImage.java b/poi-examples/src/main/java/org/apache/poi/examples/hssf/usermodel/AddDimensionedImage.java
index 129f9327da..738dd00d10 100644
--- a/poi-examples/src/main/java/org/apache/poi/examples/hssf/usermodel/AddDimensionedImage.java
+++ b/poi-examples/src/main/java/org/apache/poi/examples/hssf/usermodel/AddDimensionedImage.java
@@ -18,6 +18,13 @@
 
 package org.apache.poi.examples.hssf.usermodel;
 
-/* Placeholder - this is now handled in the Common SS example **/
+import org.apache.poi.util.Removal;
+
+/**
+ * Placeholder Class - this is now handled in the Common SS example
+ * @deprecated in 5.1.0 - use {@link org.apache.poi.examples.ss.AddDimensionedImage}
+ */
+@Removal(version="6.0.0")
+@Deprecated
 public class AddDimensionedImage extends org.apache.poi.examples.ss.AddDimensionedImage {
 }
\ No newline at end of file
diff --git a/poi-excelant/src/test/java/org/apache/poi/ss/excelant/MockExcelAntWorkbookHandler.java b/poi-excelant/src/test/java/org/apache/poi/ss/excelant/MockExcelAntWorkbookHandler.java
index d6a3a74b7d..a75506f97b 100644
--- a/poi-excelant/src/test/java/org/apache/poi/ss/excelant/MockExcelAntWorkbookHandler.java
+++ b/poi-excelant/src/test/java/org/apache/poi/ss/excelant/MockExcelAntWorkbookHandler.java
@@ -22,18 +22,19 @@ import static org.junit.jupiter.api.Assertions.assertNotNull;
 import org.apache.poi.ss.usermodel.Workbook;
 
 public class MockExcelAntWorkbookHandler implements IExcelAntWorkbookHandler {
-    public static boolean executed;
-    public static Workbook workbook;
+    public boolean executed = false;
+    public Workbook workbook = null;
 
+    public final static MockExcelAntWorkbookHandler instance = new MockExcelAntWorkbookHandler();
 
     @Override
     public void setWorkbook(Workbook workbook) {
-        MockExcelAntWorkbookHandler.workbook = workbook;
+        instance.workbook = workbook;
     }
 
     @Override
     public void execute() {
-        executed = true;
-        assertNotNull(workbook);
+        instance.executed = true;
+        assertNotNull(instance.workbook);
     }
 }
diff --git a/poi-excelant/src/test/java/org/apache/poi/ss/excelant/TestBuildFile.java b/poi-excelant/src/test/java/org/apache/poi/ss/excelant/TestBuildFile.java
index b8f34fa30c..9e580bd48e 100644
--- a/poi-excelant/src/test/java/org/apache/poi/ss/excelant/TestBuildFile.java
+++ b/poi-excelant/src/test/java/org/apache/poi/ss/excelant/TestBuildFile.java
@@ -312,8 +312,8 @@ public class TestBuildFile {
         assertLogContaining("Using input file: " + TestBuildFile.getDataDir() + "/spreadsheet/excelant.xls");
         assertLogContaining("Succeeded when evaluating 'MortgageCalculator'!$B$4.");
 
-        assertNotNull(MockExcelAntWorkbookHandler.workbook, "The workbook should have been passed to the handler");
-        assertTrue(MockExcelAntWorkbookHandler.executed, "The handler should have been executed");
+        assertNotNull(MockExcelAntWorkbookHandler.instance.workbook, "The workbook should have been passed to the handler");
+        assertTrue(MockExcelAntWorkbookHandler.instance.executed, "The handler should have been executed");
     }
 
     @Test
diff --git a/poi-ooxml/src/main/java/org/apache/poi/poifs/crypt/temp/AesZipFileZipEntrySource.java b/poi-ooxml/src/main/java/org/apache/poi/poifs/crypt/temp/AesZipFileZipEntrySource.java
index 2fb1749d4b..f66808354a 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/poifs/crypt/temp/AesZipFileZipEntrySource.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/poifs/crypt/temp/AesZipFileZipEntrySource.java
@@ -24,7 +24,6 @@ import java.io.FileOutputStream;
 import java.io.FilterOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
-import java.security.SecureRandom;
 import java.util.Enumeration;
 
 import javax.crypto.Cipher;
@@ -44,6 +43,7 @@ import org.apache.poi.poifs.crypt.CipherAlgorithm;
 import org.apache.poi.poifs.crypt.CryptoFunctions;
 import org.apache.poi.util.Beta;
 import org.apache.poi.util.IOUtils;
+import org.apache.poi.util.RandomSingleton;
 import org.apache.poi.util.TempFile;
 
 /**
@@ -106,10 +106,9 @@ public final class AesZipFileZipEntrySource implements ZipEntrySource {
 
     public static AesZipFileZipEntrySource createZipEntrySource(InputStream is) throws IOException {
         // generate session key
-        SecureRandom sr = new SecureRandom();
         byte[] ivBytes = new byte[16], keyBytes = new byte[16];
-        sr.nextBytes(ivBytes);
-        sr.nextBytes(keyBytes);
+        RandomSingleton.getInstance().nextBytes(ivBytes);
+        RandomSingleton.getInstance().nextBytes(keyBytes);
         final File tmpFile = TempFile.createTempFile("protectedXlsx", ".zip");
         copyToFile(is, tmpFile, keyBytes, ivBytes);
         IOUtils.closeQuietly(is);
diff --git a/poi-ooxml/src/main/java/org/apache/poi/poifs/crypt/temp/EncryptedTempData.java b/poi-ooxml/src/main/java/org/apache/poi/poifs/crypt/temp/EncryptedTempData.java
index d0fe43a9c8..bfc35c52d6 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/poifs/crypt/temp/EncryptedTempData.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/poifs/crypt/temp/EncryptedTempData.java
@@ -25,7 +25,6 @@ import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
-import java.security.SecureRandom;
 
 import javax.crypto.Cipher;
 import javax.crypto.CipherInputStream;
@@ -39,6 +38,7 @@ import org.apache.poi.poifs.crypt.ChainingMode;
 import org.apache.poi.poifs.crypt.CipherAlgorithm;
 import org.apache.poi.poifs.crypt.CryptoFunctions;
 import org.apache.poi.util.Beta;
+import org.apache.poi.util.RandomSingleton;
 import org.apache.poi.util.TempFile;
 
 /**
@@ -46,8 +46,8 @@ import org.apache.poi.util.TempFile;
  */
 @Beta
 public class EncryptedTempData {
-    private static Logger LOG = LogManager.getLogger(EncryptedTempData.class);
 
+    private static final Logger LOG = LogManager.getLogger(EncryptedTempData.class);
     private static final CipherAlgorithm cipherAlgorithm = CipherAlgorithm.aes128;
     private static final String PADDING = "PKCS5Padding";
     private final SecretKeySpec skeySpec;
@@ -56,11 +56,10 @@ public class EncryptedTempData {
     private CountingOutputStream outputStream;
 
     public EncryptedTempData() throws IOException {
-        SecureRandom sr = new SecureRandom();
         ivBytes = new byte[16];
         byte[] keyBytes = new byte[16];
-        sr.nextBytes(ivBytes);
-        sr.nextBytes(keyBytes);
+        RandomSingleton.getInstance().nextBytes(ivBytes);
+        RandomSingleton.getInstance().nextBytes(keyBytes);
         skeySpec = new SecretKeySpec(keyBytes, cipherAlgorithm.jceId);
         tempFile = TempFile.createTempFile("poi-temp-data", ".tmp");
     }
diff --git a/poi-ooxml/src/main/java/org/apache/poi/poifs/crypt/temp/SheetDataWriterWithDecorator.java b/poi-ooxml/src/main/java/org/apache/poi/poifs/crypt/temp/SheetDataWriterWithDecorator.java
index ea6a0519aa..a034b501fa 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/poifs/crypt/temp/SheetDataWriterWithDecorator.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/poifs/crypt/temp/SheetDataWriterWithDecorator.java
@@ -24,7 +24,6 @@ import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
-import java.security.SecureRandom;
 
 import javax.crypto.Cipher;
 import javax.crypto.CipherInputStream;
@@ -35,6 +34,7 @@ import org.apache.poi.poifs.crypt.ChainingMode;
 import org.apache.poi.poifs.crypt.CipherAlgorithm;
 import org.apache.poi.poifs.crypt.CryptoFunctions;
 import org.apache.poi.util.Beta;
+import org.apache.poi.util.RandomSingleton;
 import org.apache.poi.xssf.streaming.SheetDataWriter;
 
 @Beta
@@ -49,11 +49,10 @@ public class SheetDataWriterWithDecorator extends SheetDataWriter {
 
     void init() {
         if(skeySpec == null) {
-            SecureRandom sr = new SecureRandom();
             ivBytes = new byte[16];
             byte[] keyBytes = new byte[16];
-            sr.nextBytes(ivBytes);
-            sr.nextBytes(keyBytes);
+            RandomSingleton.getInstance().nextBytes(ivBytes);
+            RandomSingleton.getInstance().nextBytes(keyBytes);
             skeySpec = new SecretKeySpec(keyBytes, cipherAlgorithm.jceId);
         }
     }
diff --git a/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/XDDFGradientFillProperties.java b/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/XDDFGradientFillProperties.java
index ab05448eec..db53d585dc 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/XDDFGradientFillProperties.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/XDDFGradientFillProperties.java
@@ -46,7 +46,7 @@ public class XDDFGradientFillProperties implements XDDFFillProperties {
         if (props.isSetRotWithShape()) {
             return props.getRotWithShape();
         } else {
-            return null;
+            return false;
         }
     }
 
diff --git a/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/XDDFLinearShadeProperties.java b/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/XDDFLinearShadeProperties.java
index 0c3e54a245..73f4205e76 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/XDDFLinearShadeProperties.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/XDDFLinearShadeProperties.java
@@ -59,7 +59,7 @@ public class XDDFLinearShadeProperties {
         if (props.isSetScaled()) {
             return props.getScaled();
         } else {
-             return null;
+             return false;
         }
     }
 
diff --git a/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/XDDFPictureFillProperties.java b/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/XDDFPictureFillProperties.java
index 2999d51e26..02e77f1453 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/XDDFPictureFillProperties.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/XDDFPictureFillProperties.java
@@ -58,7 +58,7 @@ public class XDDFPictureFillProperties implements XDDFFillProperties {
         if (props.isSetRotWithShape()) {
             return props.getRotWithShape();
         } else {
-            return null;
+            return false;
         }
     }
 
diff --git a/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/chart/XDDFLine3DChartData.java b/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/chart/XDDFLine3DChartData.java
index 2f2e6fa738..5313e8825d 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/chart/XDDFLine3DChartData.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/chart/XDDFLine3DChartData.java
@@ -191,7 +191,7 @@ public class XDDFLine3DChartData extends XDDFChartData {
             if (series.isSetSmooth()) {
                 return series.getSmooth().getVal();
             } else {
-                return null;
+                return false;
             }
         }
 
diff --git a/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/chart/XDDFLineChartData.java b/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/chart/XDDFLineChartData.java
index 34bad10619..0a94cf96e9 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/chart/XDDFLineChartData.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/chart/XDDFLineChartData.java
@@ -174,7 +174,7 @@ public class XDDFLineChartData extends XDDFChartData {
             if (series.isSetSmooth()) {
                 return series.getSmooth().getVal();
             } else {
-                return null;
+                return false;
             }
         }
 
diff --git a/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/chart/XDDFScatterChartData.java b/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/chart/XDDFScatterChartData.java
index bb500cd20f..ba9864bf00 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/chart/XDDFScatterChartData.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/chart/XDDFScatterChartData.java
@@ -144,7 +144,7 @@ public class XDDFScatterChartData extends XDDFChartData {
             if (series.isSetSmooth()) {
                 return series.getSmooth().getVal();
             } else {
-                return null;
+                return false;
             }
         }
 
diff --git a/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/chart/XDDFSurface3DChartData.java b/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/chart/XDDFSurface3DChartData.java
index 982a104632..b61764f168 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/chart/XDDFSurface3DChartData.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/chart/XDDFSurface3DChartData.java
@@ -82,7 +82,7 @@ public class XDDFSurface3DChartData extends XDDFChartData {
        if (chart.isSetWireframe()) {
            return chart.getWireframe().getVal();
        } else {
-           return null;
+           return false;
        }
    }
 
diff --git a/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/chart/XDDFSurfaceChartData.java b/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/chart/XDDFSurfaceChartData.java
index 25e8fad31c..0547a19362 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/chart/XDDFSurfaceChartData.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/chart/XDDFSurfaceChartData.java
@@ -82,7 +82,7 @@ public class XDDFSurfaceChartData extends XDDFChartData {
        if (chart.isSetWireframe()) {
            return chart.getWireframe().getVal();
        } else {
-           return null;
+           return false;
        }
    }
 
diff --git a/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/text/XDDFBodyProperties.java b/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/text/XDDFBodyProperties.java
index 80d6f019bf..de7de30ef8 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/text/XDDFBodyProperties.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/text/XDDFBodyProperties.java
@@ -60,7 +60,7 @@ public class XDDFBodyProperties {
         if (props.isSetAnchorCtr()) {
             return props.getAnchorCtr();
         } else {
-            return null;
+            return false;
         }
     }
 
@@ -216,7 +216,7 @@ public class XDDFBodyProperties {
         if (props.isSetRtlCol()) {
             return props.getRtlCol();
         } else {
-            return null;
+            return false;
         }
     }
 
diff --git a/poi-ooxml/src/main/java/org/apache/poi/xssf/usermodel/helpers/XSSFPasswordHelper.java b/poi-ooxml/src/main/java/org/apache/poi/xssf/usermodel/helpers/XSSFPasswordHelper.java
index 167cee14ff..2933bc8c44 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/xssf/usermodel/helpers/XSSFPasswordHelper.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/xssf/usermodel/helpers/XSSFPasswordHelper.java
@@ -19,7 +19,6 @@
 
 package org.apache.poi.xssf.usermodel.helpers;
 
-import java.security.SecureRandom;
 import java.util.Arrays;
 import java.util.Base64;
 import java.util.Locale;
@@ -28,7 +27,9 @@ import javax.xml.namespace.QName;
 
 import org.apache.poi.poifs.crypt.CryptoFunctions;
 import org.apache.poi.poifs.crypt.HashAlgorithm;
+import org.apache.poi.poifs.crypt.temp.EncryptedTempData;
 import org.apache.poi.util.Internal;
+import org.apache.poi.util.RandomSingleton;
 import org.apache.poi.util.StringUtil;
 import org.apache.xmlbeans.XmlCursor;
 import org.apache.xmlbeans.XmlObject;
@@ -65,8 +66,7 @@ public final class XSSFPasswordHelper {
             cur.insertAttributeWithValue(getAttrName(prefix, "password"),
                                          String.format(Locale.ROOT, "%04X", hash).toUpperCase(Locale.ROOT));
         } else {
-            SecureRandom random = new SecureRandom();
-            byte[] salt = random.generateSeed(16);
+            byte[] salt = RandomSingleton.getInstance().generateSeed(16);
     
             // Iterations specifies the number of times the hashing function shall be iteratively run (using each
             // iteration's result as the input for the next iteration).
diff --git a/poi-ooxml/src/main/java/org/apache/poi/xwpf/usermodel/XWPFSettings.java b/poi-ooxml/src/main/java/org/apache/poi/xwpf/usermodel/XWPFSettings.java
index d0ee95fb35..0ed2adbf9d 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/xwpf/usermodel/XWPFSettings.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/xwpf/usermodel/XWPFSettings.java
@@ -22,7 +22,6 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.math.BigInteger;
-import java.security.SecureRandom;
 import java.util.Arrays;
 
 import javax.xml.namespace.QName;
@@ -33,6 +32,7 @@ import org.apache.poi.ooxml.util.POIXMLUnits;
 import org.apache.poi.openxml4j.opc.PackagePart;
 import org.apache.poi.poifs.crypt.CryptoFunctions;
 import org.apache.poi.poifs.crypt.HashAlgorithm;
+import org.apache.poi.util.RandomSingleton;
 import org.apache.xmlbeans.XmlOptions;
 import org.openxmlformats.schemas.officeDocument.x2006.sharedTypes.STAlgClass;
 import org.openxmlformats.schemas.officeDocument.x2006.sharedTypes.STAlgType;
@@ -46,7 +46,6 @@ import org.openxmlformats.schemas.wordprocessingml.x2006.main.STDocProtect;
 import org.openxmlformats.schemas.wordprocessingml.x2006.main.SettingsDocument;
 
 public class XWPFSettings extends POIXMLDocumentPart {
-
     private CTSettings ctSettings;
 
     /**
@@ -258,8 +257,7 @@ public class XWPFSettings extends POIXMLDocumentPart {
             }
 
 
-            SecureRandom random = new SecureRandom();
-            byte[] salt = random.generateSeed(16);
+            byte[] salt = RandomSingleton.getInstance().generateSeed(16);
 
             // Iterations specifies the number of times the hashing function shall be iteratively run (using each
             // iteration's result as the input for the next iteration).
diff --git a/poi-ooxml/src/test/java/org/apache/poi/poifs/crypt/dsig/DummyKeystore.java b/poi-ooxml/src/test/java/org/apache/poi/poifs/crypt/dsig/DummyKeystore.java
index b5e17ac0dd..7f19686fe0 100644
--- a/poi-ooxml/src/test/java/org/apache/poi/poifs/crypt/dsig/DummyKeystore.java
+++ b/poi-ooxml/src/test/java/org/apache/poi/poifs/crypt/dsig/DummyKeystore.java
@@ -40,7 +40,6 @@ import java.security.KeyStore;
 import java.security.KeyStoreException;
 import java.security.PrivateKey;
 import java.security.PublicKey;
-import java.security.SecureRandom;
 import java.security.cert.Certificate;
 import java.security.cert.CertificateEncodingException;
 import java.security.cert.CertificateException;
@@ -57,6 +56,7 @@ import java.util.stream.Stream;
 import org.apache.poi.poifs.crypt.CryptoFunctions;
 import org.apache.poi.poifs.storage.RawDataUtil;
 import org.apache.poi.util.LocaleUtil;
+import org.apache.poi.util.RandomSingleton;
 import org.bouncycastle.asn1.DEROctetString;
 import org.bouncycastle.asn1.ocsp.OCSPObjectIdentifiers;
 import org.bouncycastle.asn1.pkcs.PrivateKeyInfo;
@@ -119,7 +119,6 @@ public class DummyKeystore {
         }
     }
 
-    private static final SecureRandom RANDOM = new SecureRandom();
     private static final String DUMMY_ALIAS = "Test";
     private static final String DUMMY_PASS = "test";
 
@@ -187,7 +186,7 @@ public class DummyKeystore {
     public KeyCertPair addEntry(String keyAlias, String keyPass, int keySize, int expiryInMonths) throws GeneralSecurityException, IOException, OperatorCreationException {
         if (!keystore.isKeyEntry(keyAlias)) {
             KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
-            keyPairGenerator.initialize(new RSAKeyGenParameterSpec(keySize, RSAKeyGenParameterSpec.F4), RANDOM);
+            keyPairGenerator.initialize(new RSAKeyGenParameterSpec(keySize, RSAKeyGenParameterSpec.F4), RandomSingleton.getInstance());
             KeyPair pair = keyPairGenerator.generateKeyPair();
 
             Date notBefore = new Date();
@@ -262,7 +261,7 @@ public class DummyKeystore {
 
         X509v3CertificateBuilder certificateGenerator = new X509v3CertificateBuilder(
             issuerName
-            , new BigInteger(128, new SecureRandom())
+            , new BigInteger(128, RandomSingleton.getInstance())
             , notBefore
             , notAfter
             , new X500Name(subjectDn)
diff --git a/poi-ooxml/src/test/java/org/apache/poi/util/tests/TestIdentifierManager.java b/poi-ooxml/src/test/java/org/apache/poi/util/tests/TestIdentifierManager.java
index 71fe575c67..4bbc64ddc5 100644
--- a/poi-ooxml/src/test/java/org/apache/poi/util/tests/TestIdentifierManager.java
+++ b/poi-ooxml/src/test/java/org/apache/poi/util/tests/TestIdentifierManager.java
@@ -75,9 +75,9 @@ class TestIdentifierManager {
     @Test
     void testReserveNew() {
         IdentifierManager manager = new IdentifierManager(10L,12L);
-        assertSame(10L,manager.reserveNew());
-        assertSame(11L,manager.reserveNew());
-        assertSame(12L,manager.reserveNew());
+        assertEquals(10L,manager.reserveNew());
+        assertEquals(11L,manager.reserveNew());
+        assertEquals(12L,manager.reserveNew());
         assertThrows(IllegalStateException.class, manager::reserveNew);
     }
 
diff --git a/poi-ooxml/src/test/java/org/apache/poi/xslf/usermodel/TestXSLFTable.java b/poi-ooxml/src/test/java/org/apache/poi/xslf/usermodel/TestXSLFTable.java
index c36035244c..88627ad6a1 100644
--- a/poi-ooxml/src/test/java/org/apache/poi/xslf/usermodel/TestXSLFTable.java
+++ b/poi-ooxml/src/test/java/org/apache/poi/xslf/usermodel/TestXSLFTable.java
@@ -31,11 +31,9 @@ import java.awt.Rectangle;
 import java.awt.geom.Rectangle2D;
 import java.awt.image.BufferedImage;
 import java.io.File;
-import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.util.List;
-import java.util.Random;
 
 import org.apache.poi.sl.draw.DrawTableShape;
 import org.apache.poi.sl.usermodel.ShapeType;
@@ -44,6 +42,7 @@ import org.apache.poi.sl.usermodel.StrokeStyle;
 import org.apache.poi.sl.usermodel.TableCell.BorderEdge;
 import org.apache.poi.sl.usermodel.TextParagraph;
 import org.apache.poi.sl.usermodel.VerticalAlignment;
+import org.apache.poi.util.RandomSingleton;
 import org.apache.poi.util.TempFile;
 import org.apache.poi.xslf.XSLFTestDataSamples;
 import org.apache.poi.xslf.util.PPTX2PNG;
@@ -143,17 +142,17 @@ class TestXSLFTable {
         String[] names = { "car", "rubber duckie", "phone", "gadget" };
         String[] desc = { "new", "used", "untouched" };
 
-        Random r = new Random();
+
 
         for (int row=1; row<=rows; row++) {
             String[] line = new String[header.length];
             line[0] = Integer.toString(row);
-            line[1] = Integer.toString(r.nextInt(1000));
-            line[2] = names[r.nextInt(names.length)];
-            line[3] = "The "+desc[r.nextInt(desc.length)]+" "+line[2]+" in "+(2017+row);
-            line[4] = "$"+r.nextInt(50000);
-            line[5] = r.nextInt(100)+"%";
-            line[6] = "$"+r.nextInt(50000);
+            line[1] = Integer.toString(RandomSingleton.getInstance().nextInt(1000));
+            line[2] = names[RandomSingleton.getInstance().nextInt(names.length)];
+            line[3] = "The "+desc[RandomSingleton.getInstance().nextInt(desc.length)]+" "+line[2]+" in "+(2017+row);
+            line[4] = "$"+RandomSingleton.getInstance().nextInt(50000);
+            line[5] = RandomSingleton.getInstance().nextInt(100)+"%";
+            line[6] = "$"+RandomSingleton.getInstance().nextInt(50000);
             System.arraycopy(line, 0, data[row], 0, header.length);
         }
 
@@ -311,7 +310,7 @@ class TestXSLFTable {
         tc0.setText("bla bla bla bla");
         tab.setColumnWidth(0, 50);
 
-        // usually text height == 88, but font rendering is plattform dependent
+        // usually text height == 88, but font rendering is platform dependent
         // so we use something more reliable
         assertTrue(tc0.getTextHeight() > 50);
         assertEquals(0, tc0.getLineWidth(), 0);
diff --git a/poi-ooxml/src/test/java/org/apache/poi/xssf/streaming/TestSXSSFWorkbook.java b/poi-ooxml/src/test/java/org/apache/poi/xssf/streaming/TestSXSSFWorkbook.java
index f4eb9e0990..f158cc61b6 100644
--- a/poi-ooxml/src/test/java/org/apache/poi/xssf/streaming/TestSXSSFWorkbook.java
+++ b/poi-ooxml/src/test/java/org/apache/poi/xssf/streaming/TestSXSSFWorkbook.java
@@ -366,9 +366,19 @@ public final class TestSXSSFWorkbook extends BaseTestXWorkbook {
                 if (i == 0) {
                     populateWorkbook(wb);
                 } else {
-                    System.gc();
-                    System.gc();
-                    System.gc();
+                    /*
+                        Code explicitly invokes garbage collection. Except for specific use in benchmarking,
+                        this is very dubious.
+
+                        In the past, situations where people have explicitly invoked the garbage collector in
+                        routines such as close or finalize methods has led to huge performance black holes.
+                        Garbage collection can be expensive. Any situation that forces hundreds or thousands
+                        of garbage collections will bring the machine to a crawl.
+                     */
+
+                    //System.gc();
+                    //System.gc();
+                    //System.gc();
                 }
 
                     wb.write(outSteam);
diff --git a/poi-scratchpad/src/test/java/org/apache/poi/hslf/usermodel/TestPictures.java b/poi-scratchpad/src/test/java/org/apache/poi/hslf/usermodel/TestPictures.java
index 918d844ec8..ebda0b8afa 100644
--- a/poi-scratchpad/src/test/java/org/apache/poi/hslf/usermodel/TestPictures.java
+++ b/poi-scratchpad/src/test/java/org/apache/poi/hslf/usermodel/TestPictures.java
@@ -34,7 +34,6 @@ import java.net.URL;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
-import java.util.Random;
 
 import javax.imageio.ImageIO;
 
@@ -53,6 +52,7 @@ import org.apache.poi.sl.image.ImageHeaderEMF;
 import org.apache.poi.sl.image.ImageHeaderPICT;
 import org.apache.poi.sl.image.ImageHeaderWMF;
 import org.apache.poi.sl.usermodel.PictureData.PictureType;
+import org.apache.poi.util.RandomSingleton;
 import org.apache.poi.util.Units;
 import org.junit.jupiter.api.Disabled;
 import org.junit.jupiter.api.Test;
@@ -497,10 +497,9 @@ public final class TestPictures {
             originalOffsets = ppt1.getPictureData().stream().mapToInt(HSLFPictureData::getOffset).toArray();
             originalNumberOfRecords = ppt1.getPictureData().get(0).bStore.getChildCount();
 
-            Random random = new Random();
             for (HSLFPictureData picture : ppt1.getPictureData()) {
                 // Bound is arbitrary and irrelevant to the test.
-                picture.bse.setOffset(random.nextInt(500_000));
+                picture.bse.setOffset(RandomSingleton.getInstance().nextInt(500_000));
             }
 
             try (HSLFSlideShow ppt2 = writeOutAndReadBack(ppt1)) {
diff --git a/poi/src/main/java/org/apache/poi/poifs/crypt/Encryptor.java b/poi/src/main/java/org/apache/poi/poifs/crypt/Encryptor.java
index d6af6d44f7..0e2581a64e 100644
--- a/poi/src/main/java/org/apache/poi/poifs/crypt/Encryptor.java
+++ b/poi/src/main/java/org/apache/poi/poifs/crypt/Encryptor.java
@@ -31,6 +31,7 @@ import org.apache.poi.poifs.filesystem.POIFSFileSystem;
 import org.apache.poi.util.GenericRecordUtil;
 
 public abstract class Encryptor implements GenericRecord {
+
     protected static final String DEFAULT_POIFS_ENTRY = Decryptor.DEFAULT_POIFS_ENTRY;
     private EncryptionInfo encryptionInfo;
     private SecretKey secretKey;
diff --git a/poi/src/main/java/org/apache/poi/poifs/crypt/agile/AgileEncryptor.java b/poi/src/main/java/org/apache/poi/poifs/crypt/agile/AgileEncryptor.java
index 4df5540517..455959451e 100644
--- a/poi/src/main/java/org/apache/poi/poifs/crypt/agile/AgileEncryptor.java
+++ b/poi/src/main/java/org/apache/poi/poifs/crypt/agile/AgileEncryptor.java
@@ -37,8 +37,6 @@ import java.io.InputStream;
 import java.io.OutputStream;
 import java.security.GeneralSecurityException;
 import java.security.MessageDigest;
-import java.security.SecureRandom;
-import java.util.Random;
 
 import javax.crypto.Cipher;
 import javax.crypto.Mac;
@@ -62,6 +60,7 @@ import org.apache.poi.util.IOUtils;
 import org.apache.poi.util.LittleEndian;
 import org.apache.poi.util.LittleEndianByteArrayOutputStream;
 import org.apache.poi.util.LittleEndianConsts;
+import org.apache.poi.util.RandomSingleton;
 import org.apache.poi.util.XMLHelper;
 import org.w3c.dom.Document;
 
@@ -81,7 +80,6 @@ public class AgileEncryptor extends Encryptor {
     @Override
     public void confirmPassword(String password) {
         // see [MS-OFFCRYPTO] - 2.3.3 EncryptionVerifier
-        Random r = new SecureRandom();
         AgileEncryptionHeader header = (AgileEncryptionHeader)getEncryptionInfo().getHeader();
         int blockSize = header.getBlockSize();
         int keySize = header.getKeySize()/8;
@@ -93,11 +91,13 @@ public class AgileEncryptor extends Encryptor {
              , newKeySalt = IOUtils.safelyAllocate(blockSize, maxLen)
              , newKeySpec = IOUtils.safelyAllocate(keySize, maxLen)
              , newIntegritySalt = IOUtils.safelyAllocate(hashSize, maxLen);
-        r.nextBytes(newVerifierSalt); // blocksize
-        r.nextBytes(newVerifier); // blocksize
-        r.nextBytes(newKeySalt); // blocksize
-        r.nextBytes(newKeySpec); // keysize
-        r.nextBytes(newIntegritySalt); // hashsize
+
+        // using a java.security.SecureRandom (and avoid allocating a new SecureRandom for each random number needed).
+        RandomSingleton.getInstance().nextBytes(newVerifierSalt); // blocksize
+        RandomSingleton.getInstance().nextBytes(newVerifier); // blocksize
+        RandomSingleton.getInstance().nextBytes(newKeySalt); // blocksize
+        RandomSingleton.getInstance().nextBytes(newKeySpec); // keysize
+        RandomSingleton.getInstance().nextBytes(newIntegritySalt); // hashsize
 
         confirmPassword(password, newKeySpec, newKeySalt, newVerifierSalt, newVerifier, newIntegritySalt);
     }
diff --git a/poi/src/main/java/org/apache/poi/poifs/crypt/binaryrc4/BinaryRC4Encryptor.java b/poi/src/main/java/org/apache/poi/poifs/crypt/binaryrc4/BinaryRC4Encryptor.java
index c048271421..9b4542ab0b 100644
--- a/poi/src/main/java/org/apache/poi/poifs/crypt/binaryrc4/BinaryRC4Encryptor.java
+++ b/poi/src/main/java/org/apache/poi/poifs/crypt/binaryrc4/BinaryRC4Encryptor.java
@@ -22,8 +22,6 @@ import java.io.IOException;
 import java.io.OutputStream;
 import java.security.GeneralSecurityException;
 import java.security.MessageDigest;
-import java.security.SecureRandom;
-import java.util.Random;
 
 import javax.crypto.Cipher;
 import javax.crypto.SecretKey;
@@ -38,6 +36,7 @@ import org.apache.poi.poifs.crypt.HashAlgorithm;
 import org.apache.poi.poifs.crypt.standard.EncryptionRecord;
 import org.apache.poi.poifs.filesystem.DirectoryNode;
 import org.apache.poi.util.LittleEndianByteArrayOutputStream;
+import org.apache.poi.util.RandomSingleton;
 
 public class BinaryRC4Encryptor extends Encryptor {
 
@@ -52,11 +51,12 @@ public class BinaryRC4Encryptor extends Encryptor {
 
     @Override
     public void confirmPassword(String password) {
-        Random r = new SecureRandom();
         byte[] salt = new byte[16];
         byte[] verifier = new byte[16];
-        r.nextBytes(salt);
-        r.nextBytes(verifier);
+
+        // using a java.security.SecureRandom (and avoid allocating a new SecureRandom for each random number needed).
+        RandomSingleton.getInstance().nextBytes(salt);
+        RandomSingleton.getInstance().nextBytes(verifier);
         confirmPassword(password, null, null, verifier, salt, null);
     }
 
diff --git a/poi/src/main/java/org/apache/poi/poifs/crypt/cryptoapi/CryptoAPIEncryptor.java b/poi/src/main/java/org/apache/poi/poifs/crypt/cryptoapi/CryptoAPIEncryptor.java
index 176f431eec..f44ec7a7be 100644
--- a/poi/src/main/java/org/apache/poi/poifs/crypt/cryptoapi/CryptoAPIEncryptor.java
+++ b/poi/src/main/java/org/apache/poi/poifs/crypt/cryptoapi/CryptoAPIEncryptor.java
@@ -22,10 +22,8 @@ import java.io.IOException;
 import java.io.OutputStream;
 import java.security.GeneralSecurityException;
 import java.security.MessageDigest;
-import java.security.SecureRandom;
 import java.util.ArrayList;
 import java.util.List;
-import java.util.Random;
 
 import javax.crypto.Cipher;
 import javax.crypto.SecretKey;
@@ -43,6 +41,7 @@ import org.apache.poi.poifs.filesystem.Entry;
 import org.apache.poi.poifs.filesystem.POIFSFileSystem;
 import org.apache.poi.util.IOUtils;
 import org.apache.poi.util.LittleEndian;
+import org.apache.poi.util.RandomSingleton;
 import org.apache.poi.util.StringUtil;
 
 public class CryptoAPIEncryptor extends Encryptor {
@@ -58,11 +57,11 @@ public class CryptoAPIEncryptor extends Encryptor {
 
     @Override
     public void confirmPassword(String password) {
-        Random r = new SecureRandom();
         byte[] salt = new byte[16];
         byte[] verifier = new byte[16];
-        r.nextBytes(salt);
-        r.nextBytes(verifier);
+        // using a java.security.SecureRandom (and avoid allocating a new SecureRandom for each random number needed).
+        RandomSingleton.getInstance().nextBytes(salt);
+        RandomSingleton.getInstance().nextBytes(verifier);
         confirmPassword(password, null, null, verifier, salt, null);
     }
 
diff --git a/poi/src/main/java/org/apache/poi/poifs/crypt/standard/StandardEncryptor.java b/poi/src/main/java/org/apache/poi/poifs/crypt/standard/StandardEncryptor.java
index 097a7bd6d7..c5f931c62a 100644
--- a/poi/src/main/java/org/apache/poi/poifs/crypt/standard/StandardEncryptor.java
+++ b/poi/src/main/java/org/apache/poi/poifs/crypt/standard/StandardEncryptor.java
@@ -28,9 +28,7 @@ import java.io.IOException;
 import java.io.OutputStream;
 import java.security.GeneralSecurityException;
 import java.security.MessageDigest;
-import java.security.SecureRandom;
 import java.util.Arrays;
-import java.util.Random;
 
 import javax.crypto.Cipher;
 import javax.crypto.CipherOutputStream;
@@ -51,6 +49,7 @@ import org.apache.poi.util.IOUtils;
 import org.apache.poi.util.LittleEndianByteArrayOutputStream;
 import org.apache.poi.util.LittleEndianConsts;
 import org.apache.poi.util.LittleEndianOutputStream;
+import org.apache.poi.util.RandomSingleton;
 import org.apache.poi.util.TempFile;
 
 public class StandardEncryptor extends Encryptor {
@@ -65,10 +64,11 @@ public class StandardEncryptor extends Encryptor {
     @Override
     public void confirmPassword(String password) {
         // see [MS-OFFCRYPTO] - 2.3.3 EncryptionVerifier
-        Random r = new SecureRandom();
         byte[] salt = new byte[16], verifier = new byte[16];
-        r.nextBytes(salt);
-        r.nextBytes(verifier);
+
+        // using a java.security.SecureRandom (and avoid allocating a new SecureRandom for each random number needed).
+        RandomSingleton.getInstance().nextBytes(salt);
+        RandomSingleton.getInstance().nextBytes(verifier);
 
         confirmPassword(password, null, null, salt, verifier, null);
     }
diff --git a/poi/src/main/java/org/apache/poi/ss/util/CellUtil.java b/poi/src/main/java/org/apache/poi/ss/util/CellUtil.java
index 283d7d4de7..99d92c4750 100644
--- a/poi/src/main/java/org/apache/poi/ss/util/CellUtil.java
+++ b/poi/src/main/java/org/apache/poi/ss/util/CellUtil.java
@@ -244,7 +244,7 @@ public final class CellUtil {
         // Copy CellStyle
         if (policy.isCopyCellStyle()) {
             if (destCell.getSheet().getWorkbook() == srcCell.getSheet().getWorkbook()) {
-                destCell.setCellStyle(srcCell == null ? null : srcCell.getCellStyle());
+                destCell.setCellStyle(srcCell.getCellStyle());
             } else {
                 CellStyle srcStyle = srcCell.getCellStyle();
                 CellStyle destStyle = context == null ? null : context.getMappedStyle(srcStyle);
diff --git a/poi/src/main/java/org/apache/poi/util/DefaultTempFileCreationStrategy.java b/poi/src/main/java/org/apache/poi/util/DefaultTempFileCreationStrategy.java
index 0252b4b684..f2e51d48ab 100644
--- a/poi/src/main/java/org/apache/poi/util/DefaultTempFileCreationStrategy.java
+++ b/poi/src/main/java/org/apache/poi/util/DefaultTempFileCreationStrategy.java
@@ -21,7 +21,6 @@ import static org.apache.poi.util.TempFile.JAVA_IO_TMPDIR;
 
 import java.io.File;
 import java.io.IOException;
-import java.security.SecureRandom;
 
 /**
  * Default implementation of the {@link TempFileCreationStrategy} used by {@link TempFile}:
@@ -41,9 +40,6 @@ public class DefaultTempFileCreationStrategy implements TempFileCreationStrategy
     /** To keep files after JVM exit, set the <code>-Dpoi.keep.tmp.files</code> JVM property */
     public static final String KEEP_FILES = "poi.keep.tmp.files";
 
-    /** random number generator to generate unique filenames */
-    private static final SecureRandom random = new SecureRandom();
-
     /** The directory where the temporary files will be created (<code>null</code> to use the default directory). */
     private File dir;
 
@@ -126,7 +122,7 @@ public class DefaultTempFileCreationStrategy implements TempFileCreationStrategy
 
         // Generate a unique new filename
         // FIXME: Java 7+: use java.nio.Files#createTempDirectory
-        final long n = random.nextLong();
+        final long n = RandomSingleton.getInstance().nextLong();
         File newDirectory = new File(dir, prefix + Long.toString(n));
         createTempDirectory(newDirectory);
 
diff --git a/poi/src/test/java/org/apache/poi/hpsf/basic/TestMetaDataIPI.java b/poi/src/test/java/org/apache/poi/hpsf/basic/TestMetaDataIPI.java
index 0767691879..0bf0b99ce7 100644
--- a/poi/src/test/java/org/apache/poi/hpsf/basic/TestMetaDataIPI.java
+++ b/poi/src/test/java/org/apache/poi/hpsf/basic/TestMetaDataIPI.java
@@ -26,7 +26,6 @@ import static org.junit.jupiter.api.Assertions.assertTrue;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.Date;
-import java.util.Random;
 
 import org.apache.commons.io.output.UnsynchronizedByteArrayOutputStream;
 import org.apache.poi.hpsf.CustomProperties;
@@ -36,6 +35,7 @@ import org.apache.poi.hpsf.PropertySetFactory;
 import org.apache.poi.hpsf.SummaryInformation;
 import org.apache.poi.poifs.filesystem.DirectoryEntry;
 import org.apache.poi.poifs.filesystem.POIFSFileSystem;
+import org.apache.poi.util.RandomSingleton;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
@@ -583,16 +583,19 @@ final class TestMetaDataIPI {
         StringBuilder sb = new StringBuilder();
         String[] umlaute = { "\u00e4", "\u00fc", "\u00f6", "\u00dc", "$", "\u00d6", "\u00dc",
                 "\u00c9", "\u00d6", "@", "\u00e7", "&" };
-        Random rand = new Random(0); // TODO - no Random - tests should be completely deterministic
         for (int i = 0; i < 5; i++) {
             sb.append(s);
             sb.append(' ');
-            char j = (char) rand.nextInt(220);
+
+            // TODO - no Random - tests should be completely deterministic
+            char j = (char) RandomSingleton.getInstance().nextInt(220);
             j += 33;
             sb.append('>');
             sb.append(Character.valueOf(j));
             sb.append('=');
-            sb.append(umlaute[rand.nextInt(umlaute.length)]);
+
+            // TODO - no Random - tests should be completely deterministic
+            sb.append(umlaute[RandomSingleton.getInstance().nextInt(umlaute.length)]);
             sb.append('<');
         }
         return sb;
diff --git a/poi/src/test/java/org/apache/poi/hssf/usermodel/TestCellStyle.java b/poi/src/test/java/org/apache/poi/hssf/usermodel/TestCellStyle.java
index 06b6eed277..7bfea1b3cf 100644
--- a/poi/src/test/java/org/apache/poi/hssf/usermodel/TestCellStyle.java
+++ b/poi/src/test/java/org/apache/poi/hssf/usermodel/TestCellStyle.java
@@ -32,7 +32,6 @@ import java.io.FileOutputStream;
 import java.io.IOException;
 import java.util.Calendar;
 import java.util.Date;
-import java.util.Random;
 import java.util.stream.Stream;
 
 import org.apache.poi.hssf.HSSFTestDataSamples;
@@ -48,6 +47,7 @@ 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.util.LocaleUtil;
+import org.apache.poi.util.RandomSingleton;
 import org.apache.poi.util.TempFile;
 import org.junit.jupiter.api.Test;
 
@@ -414,9 +414,8 @@ final class TestCellStyle {
     @Test
     void test56563() {
         Stream.of("56563a.xls", "56563b.xls").parallel().forEach(fileName -> assertDoesNotThrow(() -> {
-            Random rand = new Random();
             for(int i=0; i<10; i++) {
-                Thread.sleep(rand.nextInt(300));
+                Thread.sleep(RandomSingleton.getInstance().nextInt(300));
                 try (Workbook wb = openSample(fileName)) {
                     for (Row row : wb.getSheetAt(0)) {
                         for (Cell cell : row) {
diff --git a/poi/src/test/java/org/apache/poi/poifs/filesystem/TestFileMagic.java b/poi/src/test/java/org/apache/poi/poifs/filesystem/TestFileMagic.java
index 456ca076ac..b0da3907e7 100644
--- a/poi/src/test/java/org/apache/poi/poifs/filesystem/TestFileMagic.java
+++ b/poi/src/test/java/org/apache/poi/poifs/filesystem/TestFileMagic.java
@@ -33,9 +33,9 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
-import java.util.Random;
 
 import org.apache.poi.POIDataSamples;
+import org.apache.poi.util.RandomSingleton;
 import org.apache.poi.util.TempFile;
 import org.junit.jupiter.api.Test;
 
@@ -165,12 +165,10 @@ class TestFileMagic {
 
     @Test
     void testRandomPatterns() {
-        Random random = new Random();
-
         // just try to trash the functionality with some byte-patterns
         for(int i = 0; i < 1000;i++) {
             final byte[] data = new byte[12];
-            random.nextBytes(data);
+            RandomSingleton.getInstance().nextBytes(data);
 
             // we cannot check for UNKNOWN as we might hit valid byte-patterns here as well
             try {
diff --git a/poi/src/test/java/org/apache/poi/ss/formula/function/ExcelFileFormatDocFunctionExtractor.java b/poi/src/test/java/org/apache/poi/ss/formula/function/ExcelFileFormatDocFunctionExtractor.java
index c73c8667cd..0155ab0fe1 100644
--- a/poi/src/test/java/org/apache/poi/ss/formula/function/ExcelFileFormatDocFunctionExtractor.java
+++ b/poi/src/test/java/org/apache/poi/ss/formula/function/ExcelFileFormatDocFunctionExtractor.java
@@ -37,6 +37,7 @@ import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Set;
 import java.util.Stack;
 import java.util.zip.ZipFile;
@@ -304,7 +305,7 @@ public final class ExcelFileFormatDocFunctionExtractor {
         @Override
         public void endElement(String namespaceURI, String localName, String name) {
             String expectedName = _elemNameStack.peek();
-            if(expectedName != name) {
+            if(!Objects.equals(name, expectedName)) {
                 throw new RuntimeException("close tag mismatch");
             }
             if(matchesPath(0, HEADING_PATH_NAMES)) {
diff --git a/poi/src/test/java/org/apache/poi/util/TestIOUtils.java b/poi/src/test/java/org/apache/poi/util/TestIOUtils.java
index 5e43acaa11..5a0c5c5bdb 100644
--- a/poi/src/test/java/org/apache/poi/util/TestIOUtils.java
+++ b/poi/src/test/java/org/apache/poi/util/TestIOUtils.java
@@ -36,7 +36,6 @@ import java.io.PushbackInputStream;
 import java.nio.ByteBuffer;
 import java.nio.channels.ReadableByteChannel;
 import java.nio.charset.StandardCharsets;
-import java.util.Random;
 
 import org.apache.commons.io.output.UnsynchronizedByteArrayOutputStream;
 import org.apache.poi.EmptyFileException;
@@ -48,7 +47,7 @@ import org.junit.jupiter.api.parallel.Isolated;
 @Isolated   // this test changes global static BYTE_ARRAY_MAX_OVERRIDE
 final class TestIOUtils {
     private static File TMP;
-    private static final long LENGTH = 300 + new Random().nextInt(9000);
+    private static final long LENGTH = 300 + RandomSingleton.getInstance().nextInt(9000);
 
     @BeforeAll
     public static void setUp() throws IOException {