SUGGESTED FIX

src/share/classes/sun/nio/ch/FileChannelImpl.java
*** 58,70 ****
      private static final NativeDispatcher nd;
  
      // Memory allocation size for mapping buffers
      private static final long allocationGranularity;
  
-     // Cached field for MappedByteBuffer.isAMappedBuffer
-     private static final Field isAMappedBufferField;
- 
      // File descriptor
      private final FileDescriptor fd;
  
      // File access mode (immutable)
      private final boolean writable;
--- 58,67 ----
*** 1313,1322 ****
  
      static {
          Util.load();
          allocationGranularity = initIDs();
          nd = new FileDispatcher();
-         isAMappedBufferField = Reflect.lookupField("java.nio.MappedByteBuffer",
-                                           "isAMappedBuffer");
      }
  
  }
--- 1310,1317 ---
                                     

EVALUATION

Introduced by 4652496 in 1.4.1 and subsequently orphaned by other changes in that release.