IntervalTree does not compile with java 8

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project infinispan-objectfilter: Compilation failure
[ERROR] /home/adrian/work/infinispan22222/infinispan/object-filter/src/main/java/org/infinispan/objectfilter/impl/util/IntervalTree.java:[286,35] incompatible types: inferred type does not conform to upper bound(s)
[ERROR] inferred: K
[ERROR] upper bound(s): java.lang.Comparable<K>,K

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