[GitHub] [incubator-heron] rohanag12 opened a new pull request #3311: Flip buffers using helper method

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rohanag12 opened a new pull request #3311: Flip buffers using helper method
URL: https://github.com/apache/incubator-heron/pull/3311
 
 
   Java 8 and 11 have a small incompatible change in the `java.nio.Buffer` API. This issue crops up if Heron topologies are compiled with JDK 11, but run with Java 8.
   
   Until Java 8, calling the `flip()` method on any object of `Buffer` (or subclasses) returns a `Buffer`. For example, `ByteBuffer#flip()` returns a `Buffer` in Java 8.
   
   In Java 11, all subclasses of `Buffer` return objects of the subclass instead of `Buffer`, i.e. `ByteBuffer#flip()` returns a `ByteBuffer` in Java 11.
   
   To work around this incompatibility between Java versions, we can cast the buffers to `Buffer` before flipping, since we do not care about the return value anyways. This causes the resulting bytecode to be the same regardless of which Java version is used to compile it.

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