Design restructuring improves software quality by reorganizing design elements and reduces maintenance cost. Object-oriented metrics can help to detect design flaws and find transformations to reorganize design elements. Basically, the transformations must preserve the behavior of an initial system. This paper describes a metric based restructuring technique preserving the behavior of object-oriented designs, founded on set theory, and gives its validity by applying the technique to applications written in Java. This paper also compares the technique with a technique using simulated annealing algorithm to show its effectiveness.