Solaris

What makes you feel it is ?
LD_LIBRARY_PATH is unset by default under Solaris and should stay that way unless inside specific wrapper scripts.
This is both incorrect (you are missing a leading slash) and useless (there are no libraries in the jdk1.7.0 directory).

---------- Post updated at 15:06 ---------- Previous update was at 15:01 ----------

Sure there is a structure.
If you want the jdk1.7 to be your default java environment, just put both of these lines in your .profile or .bash_profile

Code:

PATH=/usr/jdk/instances/jdk1.7.0/bin:$PATH
export JAVA_HOME=/usr/jdk/instances/jdk1.7.0

logout and login again and you are set.

---------- Post updated at 15:21 ---------- Previous update was at 15:06 ----------

Windows has very little in common with Unix and is quite unlikely to include anything derived from Unix code outside some tcp/ip utilities borrowed from BSD.

I disagree - not that it really matters.
DOS was developed on XENIX and borrowed a lot of the underlying architecture.
Windows - up until NT - was completely layered on top of DOS 16 bit. The NT kernel continued some of UNIX-derived stuff. As WOW. I has all gone away with Windows 7.

And you are correct about JAVA_HOME. I though the OP had set it. The install seemed to be odd.

But. The point was that Solaris requires UNIX knowledge, windows requires almost no knowledge about what is going on behind the scenes. Windows power users are really well-advised to use cygwin or something like ubuntu, not Solaris, as a first time jaunt into UNIX.

Ill advised off topic post follows:

Isn't NT based on VMS? with the BSD network stack?

That depends on how you define "based on".
Microsoft hired one of the VMS main architects (David Neil Cutler) to redesign Windows and Windows NT was the result. NT was actually a pun: you add +1 to each letter of VMS and you get WNT.
Unlikely to have the whole BSD network stack but some parts of it was based on BSD licensed code. Nowadays, I guess only things like ftp, tracert and the likes might still have BSD code. See this page for details.

---------- Post updated at 18:48 ---------- Previous update was at 17:50 ----------

"borrow" is lighter than "derived from" so DOS might indeed have borrowed some Unix concepts, although I would state it really borrowed most of its design from CP/M. XENIX, originally a Unix version 7 implementation, was already a multi-task, multi-user OS with a single hierarchical file system. DOS was definitely missing all of these features.
Got it. You confused LD_LIBRARY_PATH and JAVA_HOME.

This is where my points about the origins and development of DOS come from:
XENIX -- Microsoft Short-lived Love Affair with Unix

What this huge page says in small part:
Basically from 1980 - after DOS had been put together - DOS and XENIX started on toward full compatibility. A lot of xenix was brought into DOS as memory and disk become available for machines in the early 1980's.

To be correct DOS started with Altair.