Question

suppose I have package J

moreover I create a new folder in J hence it becomes a subpackage of J, let’s say it’s J.E

suppose I have a class in J named H with protected properties, and another class named T in J.E

can class T access the protected properties of H?

Answer 1

Sub-packages are useful only as an organizational concept. They can never be used for access control; no access relationships exist between a parent package and a child package.

From the Java Language Specification:

7.1 Package Members

…

The hierarchical naming structure for
packages is intended to be convenient
for organizing related packages in a
conventional manner, but has no
significance in itself other than the
prohibition against a package having a
subpackage with the same simple name
as a top level type (§7.6) declared in
that package. There is no special
access relationship between a package
named oliver and another package named
oliver.twist, or between packages
named evelyn.wood and evelyn.waugh.

In the context of your problem, class T cannot access the protected properties of H unless T is a subclass of H.