diff --git a/poi-ooxml/src/main/java/org/apache/poi/ooxml/extractor/POIXMLExtractorFactory.java b/poi-ooxml/src/main/java/org/apache/poi/ooxml/extractor/POIXMLExtractorFactory.java
index 124a2818ed..93d7016580 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/ooxml/extractor/POIXMLExtractorFactory.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/ooxml/extractor/POIXMLExtractorFactory.java
@@ -187,11 +187,11 @@ public final class POIXMLExtractorFactory implements ExtractorProvider {
             core = pkg.getRelationshipsByType(CORE_DOCUMENT_REL);
 
             // If nothing was found, try some of the other OOXML-based core types
-            if (core.size() == 0) {
+            if (core.isEmpty()) {
                 // Could it be an OOXML-Strict one?
                 core = pkg.getRelationshipsByType(STRICT_DOCUMENT_REL);
             }
-            if (core.size() == 0) {
+            if (core.isEmpty()) {
                 // Could it be a visio one?
                 core = pkg.getRelationshipsByType(VISIO_DOCUMENT_REL);
                 if (core.size() == 1) {
diff --git a/poi-ooxml/src/main/java/org/apache/poi/openxml4j/opc/OPCPackage.java b/poi-ooxml/src/main/java/org/apache/poi/openxml4j/opc/OPCPackage.java
index a96b8d59d0..b19b3c1d08 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/openxml4j/opc/OPCPackage.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/openxml4j/opc/OPCPackage.java
@@ -1351,7 +1351,7 @@ public abstract class OPCPackage implements RelationshipSource, Closeable {
 
     @Override
     public boolean hasRelationships() {
-        return (relationships.size() > 0);
+        return !relationships.isEmpty();
     }
 
     @Override
@@ -1644,7 +1644,7 @@ public abstract class OPCPackage implements RelationshipSource, Closeable {
     public boolean isStrictOoxmlFormat() {
         PackageRelationshipCollection coreDocRelationships = getRelationshipsByType(
                 PackageRelationshipTypes.STRICT_CORE_DOCUMENT);
-        return coreDocRelationships.size() > 0;
+        return !coreDocRelationships.isEmpty();
     }
 
     /**
diff --git a/poi-ooxml/src/main/java/org/apache/poi/openxml4j/opc/PackagePart.java b/poi-ooxml/src/main/java/org/apache/poi/openxml4j/opc/PackagePart.java
index 2aaf907d5e..70f5654ddd 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/openxml4j/opc/PackagePart.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/openxml4j/opc/PackagePart.java
@@ -442,8 +442,7 @@ public abstract class PackagePart implements RelationshipSource, Comparable<Pack
      */
     @Override
     public boolean hasRelationships() {
-        return (!this._isRelationshipPart && (_relationships != null && _relationships
-                .size() > 0));
+        return (!this._isRelationshipPart && (_relationships != null && !_relationships.isEmpty()));
     }
 
     /**
diff --git a/poi-ooxml/src/main/java/org/apache/poi/xslf/usermodel/XSLFSlideShow.java b/poi-ooxml/src/main/java/org/apache/poi/xslf/usermodel/XSLFSlideShow.java
index 79ffdb1c44..f6bf6b563b 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/xslf/usermodel/XSLFSlideShow.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/xslf/usermodel/XSLFSlideShow.java
@@ -195,7 +195,7 @@ public class XSLFSlideShow extends POIXMLDocument {
             throw new IllegalStateException(e);
         }
 
-        if(notes.size() == 0) {
+        if(notes.isEmpty()) {
             // No notes for this slide
             return null;
         }
@@ -239,7 +239,7 @@ public class XSLFSlideShow extends POIXMLDocument {
             throw new IllegalStateException(e);
         }
 
-        if(commentRels.size() == 0) {
+        if(commentRels.isEmpty()) {
             // No comments for this slide
             return null;
         }
diff --git a/poi-ooxml/src/main/java/org/apache/poi/xssf/eventusermodel/XSSFBReader.java b/poi-ooxml/src/main/java/org/apache/poi/xssf/eventusermodel/XSSFBReader.java
index deebf72836..d9a24bb855 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/xssf/eventusermodel/XSSFBReader.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/xssf/eventusermodel/XSSFBReader.java
@@ -158,7 +158,7 @@ public class XSSFBReader extends XSSFReader {
             try {
                 PackageRelationshipCollection commentsList =
                         sheetPkg.getRelationshipsByType(XSSFRelation.SHEET_COMMENTS.getRelation());
-                if (commentsList.size() > 0) {
+                if (!commentsList.isEmpty()) {
                     PackageRelationship comments = commentsList.getRelationship(0);
                     if (comments == null || comments.getTargetURI() == null) {
                         return null;
diff --git a/poi-ooxml/src/main/java/org/apache/poi/xssf/eventusermodel/XSSFReader.java b/poi-ooxml/src/main/java/org/apache/poi/xssf/eventusermodel/XSSFReader.java
index 4f668aa0f7..220f5b89c4 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/xssf/eventusermodel/XSSFReader.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/xssf/eventusermodel/XSSFReader.java
@@ -373,7 +373,7 @@ public class XSSFReader {
             try {
                 PackageRelationshipCollection commentsList =
                         sheetPkg.getRelationshipsByType(XSSFRelation.SHEET_COMMENTS.getRelation());
-                if (commentsList.size() > 0) {
+                if (!commentsList.isEmpty()) {
                     PackageRelationship comments = commentsList.getRelationship(0);
                     PackagePartName commentsName = PackagingURIHelper.createPartName(comments.getTargetURI());
                     PackagePart commentsPart = sheetPkg.getPackage().getPart(commentsName);
@@ -401,7 +401,8 @@ public class XSSFReader {
             // Do we have a shapes relationship? (Only ever one if so)
             try {
                 PackageRelationshipCollection drawingsList = sheetPkg.getRelationshipsByType(XSSFRelation.DRAWINGS.getRelation());
-                for (int i = 0; i < drawingsList.size(); i++) {
+                int drawingsSize = drawingsList.size();
+                for (int i = 0; i < drawingsSize; i++) {
                     PackageRelationship drawings = drawingsList.getRelationship(i);
                     PackagePartName drawingsName = PackagingURIHelper.createPartName(drawings.getTargetURI());
                     PackagePart drawingsPart = sheetPkg.getPackage().getPart(drawingsName);
diff --git a/poi-ooxml/src/test/java/org/apache/poi/openxml4j/opc/TestPackageThumbnail.java b/poi-ooxml/src/test/java/org/apache/poi/openxml4j/opc/TestPackageThumbnail.java
index 37b2885b5f..81c78f41dc 100644
--- a/poi-ooxml/src/test/java/org/apache/poi/openxml4j/opc/TestPackageThumbnail.java
+++ b/poi-ooxml/src/test/java/org/apache/poi/openxml4j/opc/TestPackageThumbnail.java
@@ -17,6 +17,7 @@
 
 package org.apache.poi.openxml4j.opc;
 
+import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNotEquals;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.junit.jupiter.api.Assertions.fail;
@@ -50,7 +51,7 @@ public final class TestPackageThumbnail {
 
             // Open the newly created file to check core properties saved values.
             try (OPCPackage p2 = OPCPackage.open(outputFile.getAbsolutePath(), PackageAccess.READ)) {
-                assertNotEquals(0, p2.getRelationshipsByType(PackageRelationshipTypes.THUMBNAIL).size(),
+                assertFalse(p2.getRelationshipsByType(PackageRelationshipTypes.THUMBNAIL).isEmpty(),
                     "Thumbnail not added to the package !");
                 p2.revert();
             }