Enhance ExtensionAvailabilityCache ; Expose extension count in GLContext (and clean up)

- GLContext
  - Expose isFunctionAvailable(), isExtensionAvailable(),
           getPlatformExtensionCount(), getGLExtensionCount()
  - sort methods a bit

ExtensionAvailabilityCache:
  - Favor StringBuilder instead of StringBuffer (faster)
  - Resuse set's
  - Hold dedicated counts of extensions, platform and GL

8 files changed, 150 insertions, 106 deletions

diff --git a/src/jogl/classes/com/jogamp/opengl/JoglVersion.java b/src/jogl/classes/com/jogamp/opengl/JoglVersion.java
index bf7eb0770..40790e770 100644
--- a/src/jogl/classes/com/jogamp/opengl/JoglVersion.java
+++ b/src/jogl/classes/com/jogamp/opengl/JoglVersion.java
@@ -123,29 +123,29 @@ public class JoglVersion extends JogampVersion {
                 .append(device.getType()).append(", connection ").append(device.getConnection()).append("]: ").append(Platform.getNewline());
         GLProfile.glAvailabilityToString(device, sb, "\t", 1);        
         sb.append(Platform.getNewline());
-        sb.append("Swap Interval ").append(gl.getSwapInterval());
+        sb.append("Swap Interval  ").append(gl.getSwapInterval());
         sb.append(Platform.getNewline());
-        sb.append("GL Profile    ").append(gl.getGLProfile());
+        sb.append("GL Profile     ").append(gl.getGLProfile());
         sb.append(Platform.getNewline());
-        sb.append("CTX VERSION   ").append(gl.getContext().getGLVersion());
+        sb.append("CTX VERSION    ").append(gl.getContext().getGLVersion());
         sb.append(Platform.getNewline());
-        sb.append("GL            ").append(gl);
+        sb.append("GL             ").append(gl);
         sb.append(Platform.getNewline());
-        sb.append("GL_VENDOR     ").append(gl.glGetString(GL.GL_VENDOR));
+        sb.append("GL_VENDOR      ").append(gl.glGetString(GL.GL_VENDOR));
         sb.append(Platform.getNewline());
-        sb.append("GL_RENDERER   ").append(gl.glGetString(GL.GL_RENDERER));
+        sb.append("GL_RENDERER    ").append(gl.glGetString(GL.GL_RENDERER));
         sb.append(Platform.getNewline());
-        sb.append("GL_VERSION    ").append(gl.glGetString(GL.GL_VERSION));
+        sb.append("GL_VERSION     ").append(gl.glGetString(GL.GL_VERSION));
         sb.append(Platform.getNewline());        
-        sb.append("GL_EXTENSIONS ");
+        sb.append("GL_EXTENSIONS  ").append(ctx.getGLExtensionCount());
         sb.append(Platform.getNewline());
-        sb.append("              ").append(ctx.getGLExtensionsString());
+        sb.append("               ").append(ctx.getGLExtensionsString());
         sb.append(Platform.getNewline());
-        sb.append("GLX_EXTENSIONS");
+        sb.append("GLX_EXTENSIONS ").append(ctx.getPlatformExtensionCount());
         sb.append(Platform.getNewline());
-        sb.append("              ").append(ctx.getPlatformExtensionsString());
+        sb.append("               ").append(ctx.getPlatformExtensionsString());
         sb.append(Platform.getNewline());
-        sb.append("GLSL          ").append(gl.hasGLSL()).append(", shader-compiler: ").append(gl.isFunctionAvailable("glCompileShader"));
+        sb.append("GLSL           ").append(gl.hasGLSL()).append(", shader-compiler: ").append(gl.isFunctionAvailable("glCompileShader"));
         sb.append(Platform.getNewline());
         sb.append(VersionUtil.SEPERATOR);
 
diff --git a/src/jogl/classes/javax/media/opengl/GLContext.java b/src/jogl/classes/javax/media/opengl/GLContext.java
index 0cf92fb14..41acf3e37 100644
--- a/src/jogl/classes/javax/media/opengl/GLContext.java
+++ b/src/jogl/classes/javax/media/opengl/GLContext.java
@@ -426,12 +426,43 @@ public abstract class GLContext {
     return sb;
   }
 
+  /**
+   * Returns true if the specified OpenGL core- or extension-function can be
+   * successfully called using this GL context given the current host (OpenGL
+   * <i>client</i>) and display (OpenGL <i>server</i>) configuration.
+   *
+   * See {@link GL#isFunctionAvailable(String)} for more details.
+   *
+   * @param glFunctionName the name of the OpenGL function (e.g., use
+   * "glPolygonOffsetEXT" or "glPolygonOffset" to check if the {@link
+   * javax.media.opengl.GL#glPolygonOffset(float,float)} is available).
+   */
+  public abstract boolean isFunctionAvailable(String glFunctionName);
+  
+  /**
+   * Returns true if the specified OpenGL extension can be
+   * successfully called using this GL context given the current host (OpenGL
+   * <i>client</i>) and display (OpenGL <i>server</i>) configuration.
+   *
+   * See {@link GL#isExtensionAvailable(String)} for more details.
+   *
+   * @param glExtensionName the name of the OpenGL extension (e.g.,
+   * "GL_VERTEX_PROGRAM_ARB").
+   */
+  public abstract boolean isExtensionAvailable(String glExtensionName);
+  
+  /** Returns the number of platform extensions */
+  public abstract int getPlatformExtensionCount();
+  
   /** Returns a non-null (but possibly empty) string containing the
       space-separated list of available platform-dependent (e.g., WGL,
       GLX) extensions. Can only be called while this context is
       current. */
   public abstract String getPlatformExtensionsString();
 
+  /** Returns the number of OpenGL extensions */
+  public abstract int getGLExtensionCount();
+  
   /** Returns a non-null (but possibly empty) string containing the
       space-separated list of available extensions.
       Can only be called while this context is current.
@@ -440,14 +471,6 @@ public abstract class GLContext {
    */
   public abstract String getGLExtensionsString();
 
-  public final int getGLVersionMajor() { return ctxMajorVersion; }
-  public final int getGLVersionMinor() { return ctxMinorVersion; }
-  public final boolean isGLCompatibilityProfile() { return ( 0 != ( CTX_PROFILE_COMPAT & ctxOptions ) ); }
-  public final boolean isGLCoreProfile()          { return ( 0 != ( CTX_PROFILE_CORE   & ctxOptions ) ); }
-  public final boolean isGLForwardCompatible()    { return ( 0 != ( CTX_OPTION_FORWARD & ctxOptions ) ); }
-  public final boolean isGLDebugEnabled()         { return ( 0 != ( CTX_OPTION_DEBUG & ctxOptions ) ); }
-  public final boolean isCreatedWithARBMethod()   { return ( 0 != ( CTX_IS_ARB_CREATED & ctxOptions ) ); }
-
   /**
    * @return Additional context creation flags, supported: {@link GLContext#CTX_OPTION_DEBUG}.
    */
@@ -510,6 +533,27 @@ public abstract class GLContext {
     return ctxVersionString;
   }
 
+  public final int getGLVersionMajor() { return ctxMajorVersion; }
+  public final int getGLVersionMinor() { return ctxMinorVersion; }
+  public final boolean isGLCompatibilityProfile() { return ( 0 != ( CTX_PROFILE_COMPAT & ctxOptions ) ); }
+  public final boolean isGLCoreProfile()          { return ( 0 != ( CTX_PROFILE_CORE   & ctxOptions ) ); }
+  public final boolean isGLForwardCompatible()    { return ( 0 != ( CTX_OPTION_FORWARD & ctxOptions ) ); }
+  public final boolean isGLDebugEnabled()         { return ( 0 != ( CTX_OPTION_DEBUG & ctxOptions ) ); }
+  public final boolean isCreatedWithARBMethod()   { return ( 0 != ( CTX_IS_ARB_CREATED & ctxOptions ) ); }
+  
+  /**
+   * @return true if this context is an ES2 context or implements 
+   *         the extension <code>GL_ARB_ES2_compatibility</code>, otherwise false 
+   */
+  public final boolean isGLES2Compatible() {
+      return 0 != ( ctxOptions & CTX_IMPL_ES2_COMPAT ) ;
+  }
+  
+  public final boolean hasGLSL() {
+      return isGL2ES2() ;
+  }
+
+
   public final boolean isGL4bc() {
       return ctxMajorVersion>=4 && 0 != (ctxOptions & CTX_IS_ARB_CREATED)
                                 && 0 != (ctxOptions & CTX_PROFILE_COMPAT);
@@ -560,18 +604,6 @@ public abstract class GLContext {
       return isGL2GL3() || isGLES2() ;
   }
 
-  /**
-   * @return true if this context is an ES2 context or implements 
-   *         the extension <code>GL_ARB_ES2_compatibility</code>, otherwise false 
-   */
-  public final boolean isGLES2Compatible() {
-      return 0 != ( ctxOptions & CTX_IMPL_ES2_COMPAT ) ;
-  }
-  
-  public final boolean hasGLSL() {
-      return isGL2ES2() ;
-  }
-
   public final void setSwapInterval(int interval) {
     if (!isCurrent()) {
         throw new GLException("This context is not current. Current context: "+getCurrent()+", this context "+this);
diff --git a/src/jogl/classes/jogamp/opengl/ExtensionAvailabilityCache.java b/src/jogl/classes/jogamp/opengl/ExtensionAvailabilityCache.java
index 41366c9a8..55dd0fe11 100644
--- a/src/jogl/classes/jogamp/opengl/ExtensionAvailabilityCache.java
+++ b/src/jogl/classes/jogamp/opengl/ExtensionAvailabilityCache.java
@@ -51,7 +51,6 @@ import java.util.*;
  */
 final class ExtensionAvailabilityCache {
   protected static final boolean DEBUG = GLContextImpl.DEBUG;
-  private static final boolean DEBUG_AVAILABILITY = Debug.isPropertyDefined("jogl.debug.ExtensionAvailabilityCache", true);
 
   ExtensionAvailabilityCache(GLContextImpl context)
   {
@@ -67,8 +66,12 @@ final class ExtensionAvailabilityCache {
     if(DEBUG) {
         System.out.println("ExtensionAvailabilityCache: Flush availability OpenGL "+context.getGLVersion());
     }
-    availableExtensionCache.clear();
     initialized = false;
+    glExtensions = null;
+    glExtensionCount = 0;
+    glXExtensions = null;
+    glXExtensionCount = 0;
+    availableExtensionCache.clear();
   }
 
   /**
@@ -83,8 +86,9 @@ final class ExtensionAvailabilityCache {
     return initialized && !availableExtensionCache.isEmpty() ;
   }
 
-  final int getSize() {
-    return initialized ? availableExtensionCache.size() : 0 ;
+  final int getTotalExtensionCount() {
+    initAvailableExtensions();
+    return availableExtensionCache.size();
   }
   
   final boolean isExtensionAvailable(String glExtensionName) {
@@ -92,11 +96,21 @@ final class ExtensionAvailabilityCache {
     return availableExtensionCache.contains(mapGLExtensionName(glExtensionName));
   }
 
+  final int getPlatformExtensionCount() {
+    initAvailableExtensions();
+    return glXExtensionCount;
+  }
+  
   final String getPlatformExtensionsString() {
     initAvailableExtensions();
     return glXExtensions;
   }
 
+  final int getGLExtensionCount() {
+    initAvailableExtensions();
+    return glExtensionCount;
+  }
+  
   final String getGLExtensionsString() {
     initAvailableExtensions();
     if(DEBUG) {
@@ -133,62 +147,71 @@ final class ExtensionAvailabilityCache {
                            ", use "+ ( useGetStringi ? "glGetStringi" : "glGetString" ) );
       }
 
-      StringBuffer sb = new StringBuffer();
+      HashSet<String> glExtensionSet = new HashSet<String>(gl.isGLES() ? 50 : 320); // far less gl extension expected on mobile 
       if(useGetStringi) {
         GL2GL3 gl2gl3 = gl.getGL2GL3();
-        int[] numExtensions = { 0 } ;
-        gl2gl3.glGetIntegerv(GL2GL3.GL_NUM_EXTENSIONS, numExtensions, 0);
-        for (int i = 0; i < numExtensions[0]; i++) {
-            sb.append(gl2gl3.glGetStringi(GL.GL_EXTENSIONS, i));
-            if(i < numExtensions[0]) {
-                sb.append(" ");
-            }
+        final int count;
+        {
+            int[] val = { 0 } ;
+            gl2gl3.glGetIntegerv(GL2GL3.GL_NUM_EXTENSIONS, val, 0);
+            count = val[0];
         }
-        if (DEBUG) {
-            System.err.println(getThreadName() + ":ExtensionAvailabilityCache: GL_EXTENSIONS: "+numExtensions[0]);
+        StringBuilder sb = new StringBuilder();
+        for (int i = 0; i < count; i++) {
+            if(i > 0) {
+                sb.append(" ");                
+            }
+            final String ext = gl2gl3.glGetStringi(GL.GL_EXTENSIONS, i);
+            glExtensionSet.add(ext);
+            sb.append(ext);
         }
-        if(0==numExtensions[0]) {
+        if(0==count || sb.length()==0) {
             // fall back ..
             useGetStringi=false;
+        } else {
+            glExtensions = sb.toString();
         }
       }
       if(!useGetStringi) {
-        sb.append(gl.glGetString(GL.GL_EXTENSIONS));
+          glExtensions = gl.glGetString(GL.GL_EXTENSIONS);
+          if(null != glExtensions) {
+              StringTokenizer tok = new StringTokenizer(glExtensions);
+              while (tok.hasMoreTokens()) {
+                  glExtensionSet.add(tok.nextToken().trim());
+              }
+          }
+      }
+      glExtensionCount = glExtensionSet.size(); 
+      if (DEBUG) {
+          System.err.println(getThreadName() + ":ExtensionAvailabilityCache: GL_EXTENSIONS: "+glExtensionCount);
       }
-      glExtensions = sb.toString();
       
       // Platform Extensions
+      HashSet<String> glXExtensionSet = new HashSet<String>(50);
       {         
-          // unify platform extension .. might have duplicates
-          HashSet<String> platformSet = new HashSet<String>(50);
+          // unify platform extension .. might have duplicates          
           StringTokenizer tok = new StringTokenizer(context.getPlatformExtensionsStringImpl().toString());
           while (tok.hasMoreTokens()) {
-              platformSet.add(tok.nextToken().trim());              
+              glXExtensionSet.add(tok.nextToken().trim());              
           }
-          final StringBuffer sb2 = new StringBuffer();
-          for(Iterator<String> iter = platformSet.iterator(); iter.hasNext(); ) {
-              sb2.append(iter.next()).append(" ");
+          final StringBuilder sb = new StringBuilder();
+          for(Iterator<String> iter = glXExtensionSet.iterator(); iter.hasNext(); ) {
+              sb.append(iter.next());
+              if(iter.hasNext()) {
+                  sb.append(" ");                
+              }
           }
-          glXExtensions = sb2.toString();
-      }
-      sb.append(" ");
-      sb.append(glXExtensions);
-
-      String allAvailableExtensions = sb.toString();
-      if (DEBUG_AVAILABILITY) {
-        System.err.println(getThreadName() + ":ExtensionAvailabilityCache: GL vendor: " + gl.glGetString(GL.GL_VENDOR));
-      }
-      StringTokenizer tok = new StringTokenizer(allAvailableExtensions);
-      while (tok.hasMoreTokens()) {
-        String availableExt = tok.nextToken().trim();
-        availableExt = availableExt.intern();
-        availableExtensionCache.add(availableExt);
-        if (DEBUG_AVAILABILITY) {
-          System.err.println(getThreadName() + ":ExtensionAvailabilityCache: Available: " + availableExt);
-        }
+          glXExtensions = sb.toString();
+          glXExtensionCount = glXExtensionSet.size();
       }
+      
+      availableExtensionCache.addAll(glExtensionSet);
+      availableExtensionCache.addAll(glXExtensionSet);
+      
       if (DEBUG) {
-        System.err.println(getThreadName() + ":ExtensionAvailabilityCache: ALL EXTENSIONS: "+availableExtensionCache.size());
+          System.err.println(getThreadName() + ":ExtensionAvailabilityCache: GLX_EXTENSIONS: "+glXExtensionCount);
+          System.err.println(getThreadName() + ":ExtensionAvailabilityCache: GL vendor: " + gl.glGetString(GL.GL_VENDOR));
+          System.err.println(getThreadName() + ":ExtensionAvailabilityCache: ALL EXTENSIONS: "+availableExtensionCache.size());
       }
 
       if(!context.isGLES()) {
@@ -227,7 +250,9 @@ final class ExtensionAvailabilityCache {
 
   private boolean initialized = false;
   private String glExtensions = null;
+  private int glExtensionCount = 0;
   private String glXExtensions = null;
+  private int glXExtensionCount = 0;
   private HashSet<String> availableExtensionCache = new HashSet<String>(50);
   private GLContextImpl context;
 
diff --git a/src/jogl/classes/jogamp/opengl/GLContextImpl.java b/src/jogl/classes/jogamp/opengl/GLContextImpl.java
index 7766214b4..f33c2bdb1 100644
--- a/src/jogl/classes/jogamp/opengl/GLContextImpl.java
+++ b/src/jogl/classes/jogamp/opengl/GLContextImpl.java
@@ -996,7 +996,7 @@ public abstract class GLContextImpl extends GLContext {
     if(null !=  eCache) {
         extensionAvailability = eCache;
         if(DEBUG) {
-            System.err.println(getThreadName() + ": !!! GLContext GL ExtensionAvailabilityCache reusing key("+contextFQN+") -> "+toHexString(eCache.hashCode()) + " - entries: "+eCache.getSize());
+            System.err.println(getThreadName() + ": !!! GLContext GL ExtensionAvailabilityCache reusing key("+contextFQN+") -> "+toHexString(eCache.hashCode()) + " - entries: "+eCache.getTotalExtensionCount());
         }
     } else {
         extensionAvailability = new ExtensionAvailabilityCache(this);
@@ -1004,7 +1004,7 @@ public abstract class GLContextImpl extends GLContext {
         synchronized(mappedContextTypeObjectLock) {
             mappedExtensionAvailabilityCache.put(contextFQN, extensionAvailability);
             if(DEBUG) {
-                System.err.println(getThreadName() + ": !!! GLContext GL ExtensionAvailabilityCache mapping key("+contextFQN+") -> "+toHexString(extensionAvailability.hashCode()) + " - entries: "+extensionAvailability.getSize());
+                System.err.println(getThreadName() + ": !!! GLContext GL ExtensionAvailabilityCache mapping key("+contextFQN+") -> "+toHexString(extensionAvailability.hashCode()) + " - entries: "+extensionAvailability.getTotalExtensionCount());
             }
         }
     }    
@@ -1047,19 +1047,8 @@ public abstract class GLContextImpl extends GLContext {
    */
   protected abstract void updateGLXProcAddressTable();
 
-  protected abstract StringBuffer getPlatformExtensionsStringImpl();
+  protected abstract StringBuilder getPlatformExtensionsStringImpl();
   
-  /**
-   * Returns true if the specified OpenGL core- or extension-function can be
-   * successfully called using this GL context given the current host (OpenGL
-   * <i>client</i>) and display (OpenGL <i>server</i>) configuration.
-   *
-   * See {@link GL#isFunctionAvailable(String)} for more details.
-   *
-   * @param glFunctionName the name of the OpenGL function (e.g., use
-   * "glPolygonOffsetEXT" or "glPolygonOffset" to check if the {@link
-   * javax.media.opengl.GL#glPolygonOffset(float,float)} is available).
-   */
   public final boolean isFunctionAvailable(String glFunctionName) {
     // Check GL 1st (cached)
     ProcAddressTable pTable = getGLProcAddressTable(); // null if ctx not created once
@@ -1098,16 +1087,6 @@ public abstract class GLContextImpl extends GLContext {
     return false;
   }
 
-  /**
-   * Returns true if the specified OpenGL extension can be
-   * successfully called using this GL context given the current host (OpenGL
-   * <i>client</i>) and display (OpenGL <i>server</i>) configuration.
-   *
-   * See {@link GL#isExtensionAvailable(String)} for more details.
-   *
-   * @param glExtensionName the name of the OpenGL extension (e.g.,
-   * "GL_VERTEX_PROGRAM_ARB").
-   */
   public boolean isExtensionAvailable(String glExtensionName) {
       if(null!=extensionAvailability) {
         return extensionAvailability.isExtensionAvailable(mapToRealGLExtensionName(glExtensionName));
@@ -1115,6 +1094,10 @@ public abstract class GLContextImpl extends GLContext {
       return false;
   }
 
+  public final int getPlatformExtensionCount() {
+      return null != extensionAvailability ? extensionAvailability.getPlatformExtensionCount() : 0;
+  }
+  
   public final String getPlatformExtensionsString() {
       if(null!=extensionAvailability) {
         return extensionAvailability.getPlatformExtensionsString();
@@ -1122,6 +1105,10 @@ public abstract class GLContextImpl extends GLContext {
       return null;
   }
 
+  public final int getGLExtensionCount() {
+      return null != extensionAvailability ? extensionAvailability.getGLExtensionCount() : 0;
+  }
+  
   public final String getGLExtensionsString() {
       if(null!=extensionAvailability) {
         return extensionAvailability.getGLExtensionsString();
@@ -1135,7 +1122,7 @@ public abstract class GLContextImpl extends GLContext {
       }
       return false;
   }
-
+  
   protected static String getContextFQN(AbstractGraphicsDevice device, int major, int minor, int ctxProfileBits) {
       ctxProfileBits &= ~GLContext.CTX_IMPL_ES2_COMPAT ; // remove non-key value
       return device.getUniqueID() + "-" + toHexString(composeBits(major, minor, ctxProfileBits));
diff --git a/src/jogl/classes/jogamp/opengl/egl/EGLContext.java b/src/jogl/classes/jogamp/opengl/egl/EGLContext.java
index 60766a57d..24095c749 100644
--- a/src/jogl/classes/jogamp/opengl/egl/EGLContext.java
+++ b/src/jogl/classes/jogamp/opengl/egl/EGLContext.java
@@ -248,8 +248,8 @@ public abstract class EGLContext extends GLContextImpl {
         }
     }
   
-    protected final StringBuffer getPlatformExtensionsStringImpl() {
-        StringBuffer sb = new StringBuffer();        
+    protected final StringBuilder getPlatformExtensionsStringImpl() {
+        StringBuilder sb = new StringBuilder();        
         if (!eglQueryStringInitialized) {
           eglQueryStringAvailable =
             getDrawableImpl().getGLDynamicLookupHelper().dynamicLookupFunction("eglQueryString") != 0;
diff --git a/src/jogl/classes/jogamp/opengl/macosx/cgl/MacOSXCGLContext.java b/src/jogl/classes/jogamp/opengl/macosx/cgl/MacOSXCGLContext.java
index 1503aa73d..279a5b9d7 100644
--- a/src/jogl/classes/jogamp/opengl/macosx/cgl/MacOSXCGLContext.java
+++ b/src/jogl/classes/jogamp/opengl/macosx/cgl/MacOSXCGLContext.java
@@ -322,8 +322,8 @@ public abstract class MacOSXCGLContext extends GLContextImpl
     }
   }
     
-  protected final StringBuffer getPlatformExtensionsStringImpl() {
-    return new StringBuffer();
+  protected final StringBuilder getPlatformExtensionsStringImpl() {
+    return new StringBuilder();
   }
     
   public boolean isExtensionAvailable(String glExtensionName) {
diff --git a/src/jogl/classes/jogamp/opengl/windows/wgl/WindowsWGLContext.java b/src/jogl/classes/jogamp/opengl/windows/wgl/WindowsWGLContext.java
index b2be87f4f..66c203a44 100644
--- a/src/jogl/classes/jogamp/opengl/windows/wgl/WindowsWGLContext.java
+++ b/src/jogl/classes/jogamp/opengl/windows/wgl/WindowsWGLContext.java
@@ -421,8 +421,8 @@ public class WindowsWGLContext extends GLContextImpl {
     }
   }
   
-  protected final StringBuffer getPlatformExtensionsStringImpl() {
-    StringBuffer sb = new StringBuffer();
+  protected final StringBuilder getPlatformExtensionsStringImpl() {
+    StringBuilder sb = new StringBuilder();
     
     if (!wglGetExtensionsStringEXTInitialized) {
       wglGetExtensionsStringEXTAvailable = (WGL.wglGetProcAddress("wglGetExtensionsStringEXT") != 0);
diff --git a/src/jogl/classes/jogamp/opengl/x11/glx/X11GLXContext.java b/src/jogl/classes/jogamp/opengl/x11/glx/X11GLXContext.java
index 9b154af95..d8813ed7f 100644
--- a/src/jogl/classes/jogamp/opengl/x11/glx/X11GLXContext.java
+++ b/src/jogl/classes/jogamp/opengl/x11/glx/X11GLXContext.java
@@ -465,8 +465,8 @@ public abstract class X11GLXContext extends GLContextImpl {
     }
   }
 
-  protected final StringBuffer getPlatformExtensionsStringImpl() {
-    StringBuffer sb = new StringBuffer();
+  protected final StringBuilder getPlatformExtensionsStringImpl() {
+    StringBuilder sb = new StringBuilder();
     if (DEBUG) {
       System.err.println("!!! GLX Version client version "+ GLXUtil.getClientVersionNumber()+
                          ", server: "+