JDK-8191416 : (bf) DirectByteBuffer extends MappedByteBuffer, confuses instanceof tests
  • Type: Bug
  • Component: core-libs
  • Sub-Component: java.nio
  • Priority: P4
  • Status: Closed
  • Resolution: Fixed
  • Submitted: 2017-11-16
  • Updated: 2018-03-28
  • Resolved: 2018-02-12
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JDK 11
11 b01Fixed
Related Reports
Relates :  
JDK-4833719 - (bf) Views of MappedByteBuffers are not MappedByteBuffers, and cannot be forced
Description
A long standing implementation detail is that direct ByteBuffers extend MappedByteBuffer. Now consider:

if (bb instance MappedByteBuffer) {
    ((MappedByteBuffer)bb).force();
} 

This throws UOE, as does isLoaded and the other methods defined by MappedByteBuffer.

A simple solution may be force/load/etc. to be no-ops when invoked without a backing file.