Ironically, it seems impossible to override DiffResult.toString(), which one may wish to do in order to provide alternate formats for the differences that are more compact than "lhs differs from rhs."
In my case, I wanted to support differences between Set<Integer> so that one could get output like: Object[groups: added: {1, 2}, removed: {7},name:cat->dog] Rather than: Object[groups:[3,4,7],name=cat] differs from Object[groups: [1,2,3,4],name=dog] To support this I ended up wrapping the DiffResult class because I could not extend it due to its private constructor. re: https://commons.apache.org/proper/commons-lang/apidocs/org/apache/commons/lang3/builder/DiffResult.html