InGen(10) will check if there is already an instance of TestInj1 which
was constructed with the value 10. If it exists, it is returned.
Otherwise a TestInj1 is created with 10 passed to its constructor.
This created instance is additionally stored inside the InGenFactory.
InGen(10) will check if there is already an instance of TestInj1 which was constructed with the value 10. If it exists, it is returned. Otherwise a TestInj1 is created with 10 passed to its constructor. This created instance is additionally stored inside the InGenFactory.