Improving the performance of toString() by caching the result.
Improving the performance of equals() by first checking if the QName is the
same object and then by checking whether the local names are equal before
looking at the namespace URI. Since it's more likely that the namespaces
will be equal, we can return false faster when the local names are different.
git-svn-id: https://svn.apache.org/repos/asf/xml/commons/trunk@226225 13f79535-47bb-0310-9956-ffa450edef68
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