Questions posées lors d’un entretien d’embauche pour Java Software Developer chez Mphasis

There totally 3Rounds.2 technical rounds followed by Hr round.1round questions Difference between == and .equals(),What is a Lambda Expression ? What's its use ?. Describe, in general, how java's garbage collector works ? Explain OOPs features,

interview scheduled by 3rd party agency it consisted of 3 rounds: 1st was techinecal round, then 2nd was managerial and technical round, and then 3rd will be a HR round - however I did not make through all of these.