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/render/AbstractShape.java b/src/gov/nasa/worldwind/render/AbstractShape.java
index a09c7cc5f..e7740d507 100644
--- a/src/gov/nasa/worldwind/render/AbstractShape.java
+++ b/src/gov/nasa/worldwind/render/AbstractShape.java
@@ -1542,7 +1542,7 @@ protected Extent computeExtentFromPositions(Globe globe, double verticalExaggera
             extremes = new double[] {Double.MAX_VALUE, -Double.MAX_VALUE};
             for (LatLon pos : positions)
             {
-                double elevation = pos instanceof Position ? ((Position) pos).getElevation() : 0;
+                double elevation = pos instanceof Position position ? position.getElevation() : 0;
                 if (this.getAltitudeMode() == WorldWind.RELATIVE_TO_GROUND)
                     elevation += minAndMaxElevations[1];
 
diff --git a/src/gov/nasa/worldwind/render/DrawContextImpl.java b/src/gov/nasa/worldwind/render/DrawContextImpl.java
index c24100b16..c76b95dba 100644
--- a/src/gov/nasa/worldwind/render/DrawContextImpl.java
+++ b/src/gov/nasa/worldwind/render/DrawContextImpl.java
@@ -820,7 +820,7 @@ public OrderedRenderable pollOrderedRenderables()
 //        ArrayList<OrderedRenderableEntry> declutterableArray = new ArrayList<OrderedRenderableEntry>();
 //        for (OrderedRenderableEntry ore : this.orderedRenderables)
 //        {
-//            if (ore.or instanceof Declutterable && ((Declutterable) ore.or).isEnableDecluttering())
+//            if (ore.or instanceof Declutterable declutterable && declutterable.isEnableDecluttering())
 //                declutterableArray.add(ore);
 //        }
 //
@@ -880,7 +880,7 @@ public void applyClutterFilter()
         ArrayList<OrderedRenderableEntry> declutterableArray = new ArrayList<OrderedRenderableEntry>();
         for (OrderedRenderableEntry ore : this.orderedRenderables)
         {
-            if (ore.or instanceof Declutterable && ((Declutterable) ore.or).isEnableDecluttering())
+            if (ore.or instanceof Declutterable declutterable && declutterable.isEnableDecluttering())
                 declutterableArray.add(ore);
         }
 
diff --git a/src/gov/nasa/worldwind/render/UserFacingIcon.java b/src/gov/nasa/worldwind/render/UserFacingIcon.java
index 5ff03858b..71700d8ef 100644
--- a/src/gov/nasa/worldwind/render/UserFacingIcon.java
+++ b/src/gov/nasa/worldwind/render/UserFacingIcon.java
@@ -116,7 +116,7 @@ public void setImageSource(Object imageSource)
 
     public String getPath()
     {
-        return this.getImageSource() instanceof String ? (String) this.getImageSource() : null;
+        return this.getImageSource() instanceof String imageSource ? imageSource : null;
     }
 
     public Position getPosition()