PLEASE JAVA CODE.

Page replacement takes the following approach. If no frame is free, we find one that is not currently being used and free it. We can free a frame by writing its contents to swap space and changing the page table and all other tables) to indicate that the page is no longer in memory. We can now use the freed frame to hold the page for which the process faulted. Given a reference string such as: 1, 2, 3, 4, 2, 1, 5, 6, 2, 1, 2, 4, 3, 7, 6, 6, 5, 3, 2, 1, 2, 3, 6 implement page replacement algorithms FIFO replacement, Optimal replacement, LRU replacement in a way that where user can enter number of frames, and simulate algorithms then calculate the number of page faults. In order to get full grade, explain your code using comments. You can implement the algorithms with langeage of your choice