Java libs are installed into an already prefixed path.

--- a/bindings/java/CMakeLists.txt
+++ b/bindings/java/CMakeLists.txt
@@ -189,7 +189,7 @@
       )
   endif(APPLE)
 
-  install(TARGETS plplotjavac_wrap LIBRARY DESTINATION ${JAVAWRAPPER_HARDDIR})
+  install(TARGETS plplotjavac_wrap LIBRARY DESTINATION ${JAVAWRAPPER_DIR})
 
   set(JAVA_CLASSES)
   foreach( srcfile ${JAVA_FILES_FULL} )