  We study strangeness (K^+, K^-, and Lambda) production and flow in Ni+Ni
collisions at 1-2 AGeV, based on the relativistic transport model including the
strangeness degrees of freedom. We find that strangeness spectra and flow are
sensitive to the properties of strange hadrons in nuclear medium. The
predictions of the chiral perturbation theory that the K^+ feels a weak
repulsive potential and K^- feels a strong attractive potential are in good
agreement with recent experimental data from FOPI and KaoS collaborations.
