Entropic sampling method within Wang-Landau algorithm is used for simulation of lattice models of linear polymer chains and 6-arm star-shaped polymers. The semi-phantom (i.e. nonreversal) random walk on 3D simple cubic lattice is used as a reference system. The densities of states are obtained and on their basis the temperature dependences of internal energy, heat capacity, entropy and mean square radius of gyration are calculated. Results for stars are compared with data for linear chains.