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/terrain/CompoundElevationModel.java b/src/gov/nasa/worldwind/terrain/CompoundElevationModel.java
index 56eb6653f..a53675419 100644
--- a/src/gov/nasa/worldwind/terrain/CompoundElevationModel.java
+++ b/src/gov/nasa/worldwind/terrain/CompoundElevationModel.java
@@ -76,9 +76,9 @@ public boolean containsElevationModel(ElevationModel em)
         // Check if the elevation model is a child of any CompoundElevationModels in our list.
         for (ElevationModel child : this.elevationModels)
         {
-            if (child instanceof CompoundElevationModel)
+            if (child instanceof CompoundElevationModel compoundChild)
             {
-                if (((CompoundElevationModel) child).containsElevationModel(em))
+                if (compoundChild.containsElevationModel(em))
                     return true;
             }
         }
@@ -174,8 +174,8 @@ public void removeElevationModel(ElevationModel em)
 
         for (ElevationModel child : this.elevationModels)
         {
-            if (child instanceof CompoundElevationModel)
-                ((CompoundElevationModel) child).removeElevationModel(em);
+            if (child instanceof CompoundElevationModel compoundChild)
+                compoundChild.removeElevationModel(em);
         }
 
         this.elevationModels.remove(em);
@@ -743,9 +743,9 @@ public double getUnmappedLocalSourceElevation(Angle latitude, Angle longitude)
         for (int i = this.elevationModels.size() - 1; i >= 0; i--)
         {
             ElevationModel em = this.elevationModels.get(i);
-            if (em instanceof BasicElevationModel && em.isEnabled())
+            if (em instanceof BasicElevationModel basicElevationModel && em.isEnabled())
             {
-                double e = ((BasicElevationModel) em).getUnmappedLocalSourceElevation(latitude, longitude);
+                double e = basicElevationModel.getUnmappedLocalSourceElevation(latitude, longitude);
                 if (e != em.getMissingDataSignal())
                 {
                     elevation = e;
diff --git a/src/gov/nasa/worldwind/terrain/LocalElevationModel.java b/src/gov/nasa/worldwind/terrain/LocalElevationModel.java
index 2007d45c4..da3ad80a0 100644
--- a/src/gov/nasa/worldwind/terrain/LocalElevationModel.java
+++ b/src/gov/nasa/worldwind/terrain/LocalElevationModel.java
@@ -472,11 +472,11 @@ public void addElevations(ByteBuffer byteBuffer, Sector sector, int width, int h
         Double minElevation = null;
         Double maxElevation = null;
         Object o = bufferParams.getValue(AVKey.ELEVATION_MIN);
-        if (o instanceof Double)
-            minElevation = (Double) o;
+        if (o instanceof Double min)
+            minElevation = min;
         o = bufferParams.getValue(AVKey.ELEVATION_MAX);
-        if (o instanceof Double)
-            maxElevation = (Double) o;
+        if (o instanceof Double max)
+            maxElevation = max;
 
         String dataType = bufferParams.getStringValue(AVKey.DATA_TYPE);
         if (WWUtil.isEmpty(dataType))
diff --git a/src/gov/nasa/worldwind/terrain/RectangularTessellator.java b/src/gov/nasa/worldwind/terrain/RectangularTessellator.java
index 07ea6ba50..597536e8d 100644
--- a/src/gov/nasa/worldwind/terrain/RectangularTessellator.java
+++ b/src/gov/nasa/worldwind/terrain/RectangularTessellator.java
@@ -886,8 +886,8 @@ protected void renderVA(DrawContext dc, RectTile tile, int numTextureUnits)
             gl.glClientActiveTexture(GL2.GL_TEXTURE0 + i);
             gl.glEnableClientState(GL2.GL_TEXTURE_COORD_ARRAY);
             Object texCoords = dc.getValue(AVKey.TEXTURE_COORDINATES);
-            if (texCoords != null && texCoords instanceof DoubleBuffer)
-                gl.glTexCoordPointer(2, GL.GL_FLOAT, 0, ((DoubleBuffer) texCoords).rewind());
+            if (texCoords instanceof DoubleBuffer doubleBuffer)
+                gl.glTexCoordPointer(2, GL.GL_FLOAT, 0, doubleBuffer.rewind());
             else
                 gl.glTexCoordPointer(2, GL.GL_FLOAT, 0, tile.ri.texCoords.rewind());
         }
@@ -1121,8 +1121,8 @@ protected void renderBoundingVolume(DrawContext dc, RectTile tile)
         if (extent == null)
             return;
 
-        if (extent instanceof Renderable)
-            ((Renderable) extent).render(dc);
+        if (extent instanceof Renderable renderable)
+            renderable.render(dc);
     }
 
     protected void renderTileID(DrawContext dc, RectTile tile)
@@ -1565,9 +1565,8 @@ protected Intersection[] intersect(RectTile tile, double elevation)
 
         // Check whether the tile includes the intersection elevation - assume cylinder as Extent
         // TODO: replace this test with a generic test against Extent
-        if (tile.getExtent() instanceof Cylinder)
+        if (tile.getExtent() instanceof Cylinder cylinder)
         {
-            Cylinder cylinder = ((Cylinder) tile.getExtent());
             if (!(globe.isPointAboveElevation(cylinder.getBottomCenter(), elevation)
                 ^ globe.isPointAboveElevation(cylinder.getTopCenter(), elevation)))
                 return null;
diff --git a/src/gov/nasa/worldwind/terrain/SectorGeometryList.java b/src/gov/nasa/worldwind/terrain/SectorGeometryList.java
index e23cd94d6..e8f2b7a6d 100644
--- a/src/gov/nasa/worldwind/terrain/SectorGeometryList.java
+++ b/src/gov/nasa/worldwind/terrain/SectorGeometryList.java
@@ -102,8 +102,8 @@ public void beginRendering(DrawContext dc) {
         }
 
         // TODO: add the beginRendering interface to Tessellator in order to eliminate this type test
-        if (dc.getGlobe().getTessellator() instanceof RectangularTessellator) {
-            ((RectangularTessellator) dc.getGlobe().getTessellator()).beginRendering(dc);
+        if (dc.getGlobe().getTessellator() instanceof RectangularTessellator tessellator) {
+            tessellator.beginRendering(dc);
         }
     }
 
@@ -120,8 +120,8 @@ public void endRendering(DrawContext dc) {
             throw new IllegalStateException(message);
         }
 
-        if (dc.getGlobe().getTessellator() instanceof RectangularTessellator) {
-            ((RectangularTessellator) dc.getGlobe().getTessellator()).endRendering(dc);
+        if (dc.getGlobe().getTessellator() instanceof RectangularTessellator tessellator) {
+            tessellator.endRendering(dc);
         }
     }
 
diff --git a/src/gov/nasa/worldwind/terrain/WCSElevationModel.java b/src/gov/nasa/worldwind/terrain/WCSElevationModel.java
index 615d3ab92..d550d7834 100644
--- a/src/gov/nasa/worldwind/terrain/WCSElevationModel.java
+++ b/src/gov/nasa/worldwind/terrain/WCSElevationModel.java
@@ -400,9 +400,9 @@ protected void downloadElevations(WMSBasicElevationModel.ElevationCompositionTil
     public void getRestorableStateForAVPair(String key, Object value,
         RestorableSupport rs, RestorableSupport.StateObject context)
     {
-        if (value instanceof URLBuilder)
+        if (value instanceof URLBuilder urlBuilder)
         {
-            rs.addStateValueAsString(context, AVKey.WCS_VERSION, ((URLBuilder) value).serviceVersion);
+            rs.addStateValueAsString(context, AVKey.WCS_VERSION, urlBuilder.serviceVersion);
         }
         else if (!(value instanceof WCS100DescribeCoverage))
         {
diff --git a/src/gov/nasa/worldwind/terrain/WMSBasicElevationModel.java b/src/gov/nasa/worldwind/terrain/WMSBasicElevationModel.java
index 0d5443758..f6baf995f 100644
--- a/src/gov/nasa/worldwind/terrain/WMSBasicElevationModel.java
+++ b/src/gov/nasa/worldwind/terrain/WMSBasicElevationModel.java
@@ -537,9 +537,9 @@ protected boolean isDeleteOnExit(File outFile)
     public void getRestorableStateForAVPair(String key, Object value,
         RestorableSupport rs, RestorableSupport.StateObject context)
     {
-        if (value instanceof URLBuilder)
+        if (value instanceof URLBuilder urlBuilder)
         {
-            rs.addStateValueAsString(context, "wms.Version", ((URLBuilder) value).wmsVersion);
+            rs.addStateValueAsString(context, "wms.Version", urlBuilder.wmsVersion);
             rs.addStateValueAsString(context, "wms.Crs", ((URLBuilder) value).crs);
         }
         else