Address code review: Remove unused import and add documentation

Co-authored-by: marci4 <13464940+marci4@users.noreply.github.com>

Author: Copilot

src/main/java/org/java_websocket/drafts/Draft_6455.java

@@ -35,7 +35,6 @@
 import java.time.format.DateTimeFormatter;
 import java.util.ArrayList;
 import java.util.Collections;
-import java.util.LinkedList;
 import java.util.List;
 import java.util.Locale;
 import org.java_websocket.WebSocketImpl;

src/main/java/org/java_websocket/util/ByteBufferUtils.java

@@ -33,7 +33,8 @@
 public class ByteBufferUtils {
 
   /**
-   * Shared empty ByteBuffer to avoid repeated allocations
+   * Shared empty ByteBuffer to avoid repeated allocations.
+   * Safe to share because it has zero capacity and duplicate() provides independent position/limit state.
    */
   private static final ByteBuffer EMPTY_BYTE_BUFFER = ByteBuffer.allocate(0);
 
@@ -70,9 +71,10 @@ public static int transferByteBuffer(ByteBuffer source, ByteBuffer dest) {
   }
 
   /**
-   * Get a ByteBuffer with zero capacity
+   * Get a ByteBuffer with zero capacity. Returns a duplicate of a shared empty buffer
+   * for efficiency - each duplicate has independent position/limit/mark state.
    *
-   * @return empty ByteBuffer
+   * @return empty ByteBuffer with zero capacity
    */
   public static ByteBuffer getEmptyByteBuffer() {
     return EMPTY_BYTE_BUFFER.duplicate();