A search for new heavy particles manifested as resonances in two-jet final states is presented. The data were produced in 7 TeV proton-proton collisions by the LHC and correspond to an integrated luminosity of $315\text{ }\text{ }{\mathrm{nb}}^{\ensuremath{-}1}$ collected by the ATLAS detector. No resonances were observed. Upper limits were set on the product of cross section and signal acceptance for excited-quark (${q}^{*}$) production as a function of ${q}^{*}$ mass. These exclude at the 95% C.L. the ${q}^{*}$ mass interval $0.30<{m}_{{q}^{*}}<1.26\text{ }\text{ }\mathrm{TeV}$, extending the reach of previous experiments.