Changed the constructors of Data and ObjectData to use variable length parameters.
Added JavaDoc comments to some methods and packages.
Revert "Added JavaDoc comments to some methods and packages."

This reverts commit 568feec24f628d84ca2f8901e62cb15ded9543a4.
Added JavaDoc comments to some methods and packages.
Added HeapUsage.java and HeapUsageReporter.java to show the usage of heap memory.