The relationship between shear cracks and double‐ended dislocation arrays is discussed. The density of a double‐ended dislocation array under the uniform applied shear stress was calculated by the shear‐crack conversion method. The calculated density agrees with that calculated from the dislocation model. A general method of calculating the dislocation densities near the spearheads of dislocation arrays is given. Examples are illustrated; in general, the density as well as the stress and strain fields near the spearhead of a single‐ended linear dislocation array are higher than those of a double‐ended array under the same applied stress on the slip plane.