One: Do push-ups on the floor, which is the simplest way to keep fit. You can practice as long as there is open space.
Two: If the bed board is not thin, you can sit up and sit up on the bed. Some of them may be accompanied by the sound of shaking the bed board. Pay attention to safety, and the bed board will not break.
Three: If the bed is hooked to the wall and the fence next to the bed is firm, you can do pull-ups as a horizontal bar.
If time permits, it's best to go outdoors for fitness. It's easy to influence others in the dormitory.