It started with Telephonic discussion and then 2 technical rounds. Looked like first interviewer had just read questions and came to take interview as he first asked create mutable class and then when I was describing immutable, he told create immutable class and he himself didn't know how to create one as for returning map object, I told use copy and send and he told it is not proper. Second interviewer was worse than the first one as he himself had not clarity on what he is asking. First he told have 2 remotes and 1 projector and write design so that they can interact with each other and when both are together then only 1 should work and later he added 1 remote should work for only 1 projector as you can have multiple projectors also, so when I asked about can we use some identifier, he was not ready for it and later he is saying you can use observer pattern. That even a kid can understand but how can 1 remote work for only 1 projector when both the projectors are in the same room without using any identifier that only god knows or the interviewer. Second question, create metro train card swap system. For each controller i.e. entry have 1 hop as price and keep and accumulating and during exit bill the card. I told we can store the information in the card itself as to how many controllers it has crossed as that looked simplest solution and efficient but he told card does not have these features and do you know what card is. As I didn't board Delhi metro so I didn't say anything but if you read about Delhi metro system, the data is stored in card itself as in station code and during exit out station code and the amount is subtracted based on distance traveled. Issue is the interviewer was not receptive to others design and was of very high opinion of himself