/**     * Unmaps the block from memory. See munmap(2).     *     * There isn't any portable way to unmap a memory region in Java.     * So we use the sun.nio method here.     * Note that unmapping a memory region could cause crashes if code     * continues to reference the unmapped code.  However, if we don't     * manually unmap the memory, we are dependent on the finalizer to     * do it, and we have no idea when the finalizer will run.     *     * @param buffer    The buffer to unmap.     */publicstaticvoidmunmap(MappedByteBufferbuffer){if(bufferinstanceofsun.nio.ch.DirectBuffer){sun.misc.Cleanercleaner=((sun.nio.ch.DirectBuffer)buffer).cleaner();cleaner.clean();}}

privatestaticMethodHandlecleanMethod=null;static{MethodHandles.Lookuplookup=MethodHandles.lookup();try{finalClass<?>directBufferClass=Class.forName("java.nio.DirectByteBuffer");finalMethodm=directBufferClass.getMethod("cleaner");// Set permission to the lookup class for making// a direct method handlem.setAccessible(true);// Make a direct method handleMethodHandledirectbufferCleanerMethod=lookup.unreflect(m);// Get the return type of java.nio.DirectByteBuffer// JDK8: sun.misc.Cleaner// JDK9: jdk.internal.ref.CleanerClass<?>cleanerClass=directbufferCleanerMethod.type().returnType();// Get the method (Cleaner#clean)cleanMethod=lookup.findVirtual(cleanerClass,"clean",methodType(void.class));}catch(NoSuchMethodException|IllegalAccessException|ClassNotFoundExceptionignored){}}

publicstaticvoidmunmap(MappedByteBufferbuffer){if(bufferinstanceofsun.nio.ch.DirectBuffer){if(cleanMethod!=null){try{// Execute Cleaner#cleancleanMethod.invokeExact(((sun.nio.ch.DirectBuffer)buffer).cleaner());}catch(Throwableignored){}}