Oracle Software Engineer Senior interview questions

They lot of rounds .I cleared till 4th round and still few more were left .Most of the rounds they ask the same questions ...singleton , threads , collection framework

Written test, followed by technical interview 2 rounds, then Managerial round followed by HR round. Then salary discussion. Followed by offer letter.Written test, followed by technical interview 2 rounds, then Managerial round followed by HR round. Then salary discussion. Followed by offer letter.