Interface of java used as a design pattern for object oriented software development mostly used with inheritance, in java multiple inheritance is possible only through the interface this approach is widely used with modern software development approach apart from that there is also a rough side of java's Interface which discussed in this paper, interface doesn't allow the any kind of definition under it, but there is also some other concept like parent and child class concept if such concept apply with the interface then the theory of interface has been changed in this paper a practical approach has been used for this research problem.