  We use quantum quenches to study the dynamics and thermalization of hardcore
bosons in finite one-dimensional lattices. We perform exact diagonalizations
and find that, far away from integrability, few-body observables thermalize. We
then study the breakdown of thermalization as one approaches an integrable
point. This is found to be a smooth process in which the predictions of
standard statistical mechanics continuously worsen as the system moves toward
integrability. We establish a direct connection between the presence or absence
of thermalization and the validity or failure of the eigenstate thermalization
hypothesis, respectively.
