Fix Java concoredocker to match Python behavior

[avinxshKD]

Fix Java implementation to match Python behavior

The Java version had several bugs that broke core functionality - read() only returned one value instead of the full array, write() used the wrong timestamp variable, defaultMaxTime() was trying to cast a bare integer to a List, and unchanged() didn't return anything.

Also added the missing simtime field that Python tracks globally and removed the System.exit(1) call that would crash the whole container on bad input.

Fixes #197

[avinxshKD]

@pradeeban recreated the fix for #197 as asked. Bcz commits cancled eatch other before,

plks review thanks

[pradeeban]

Why is this exception changed to a generic one? If you anticipate more than IOException, please create more targeted exceptions, rather than replacing IOException with the generic Exception.

[avinxshKD]

@pradeeban hey hve updated the catch block to use targeted exceptions:
} catch (IOException | ClassCastException | NumberFormatException e) {

These cover: file read errors, parsing failures, and type cast issues. Does this look good? or would you prefer a different approach?

Also, the CI tests are failing on test_run_command_from_project_dirin
test_cli.py , this seems to be a pre-existing issue unrelated to the Java changes.
Should I investigate that separately? pls let me know Thanks