diff --git a/.travis.yml b/.travis.yml
index 0eadda768..909b77aa1 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -6,7 +6,7 @@ language: java
 
 # Configure the build to use Oracle JDK 9
 jdk:
-  - openjdk11
+  - openjdk21
 
 # Install the Ant JUnit package, which is missing from the Travis CI environment. See the Travis documentation: https://docs.travis-ci.com/user/installing-dependencies/#Adding-APT-Packages
 addons:
diff --git a/nbproject/project.properties b/nbproject/project.properties
index fab181db5..de8a7bdfc 100644
--- a/nbproject/project.properties
+++ b/nbproject/project.properties
@@ -56,8 +56,8 @@ javac.modulepath=
 javac.processormodulepath=
 javac.processorpath=\
     ${javac.classpath}
-javac.source=11
-javac.target=11
+javac.source=21
+javac.target=21
 javac.test.classpath=\
     ${javac.classpath}:\
     ${build.classes.dir}
diff --git a/release-build.properties b/release-build.properties
index cde1c0e4d..689b78744 100644
--- a/release-build.properties
+++ b/release-build.properties
@@ -38,7 +38,7 @@ worldwind.classes.dir=${worldwind.build.dir}/classes
 worldwind.doc.dir=${worldwind.build.dir}/doc
 worldwind.jar.dir=${worldwind.build.dir}/jar
 worldwind.test.results.dir=${worldwind.build.dir}/test-results
-worldwind.jdk=11
+worldwind.jdk=21
 #worldwind.exclude.jackson=true
 
 # MIL-STD-2525 package build properties
diff --git a/release-build.xml b/release-build.xml
index 9810ad732..7948d8878 100644
--- a/release-build.xml
+++ b/release-build.xml
@@ -126,7 +126,7 @@
                 <pathelement location="gluegen-rt.jar"/>
                 <pathelement location="gdal.jar"/>
             </classpath>
-            <link href="http://download.oracle.com/javase/8/docs/api/"/>
+            <link href="https://docs.oracle.com/en/java/javase/21/docs/api/"/>
             <link href="https://jogamp.org/deployment/v2.4.0-rc-20200307/javadoc/"/>
         </javadoc>
     </target>
diff --git a/src/gov/nasa/worldwind/event/BulkRetrievalEvent.java b/src/gov/nasa/worldwind/event/BulkRetrievalEvent.java
index 3e317cf5e..ab1a48548 100644
--- a/src/gov/nasa/worldwind/event/BulkRetrievalEvent.java
+++ b/src/gov/nasa/worldwind/event/BulkRetrievalEvent.java
@@ -74,7 +74,7 @@ public BulkRetrievalEvent(BulkRetrievable source, String eventType, String item)
      */
     public BulkRetrievable getSource()
     {
-        return super.getSource() instanceof BulkRetrievable ? (BulkRetrievable) super.getSource() : null;
+        return super.getSource() instanceof BulkRetrievable bulkRetrievable ? bulkRetrievable : null;
     }
 
     /**