There's a small startup cost associated with private static final ObjectStreamField[] serialPersistentFields, most of which boils down to the fact that the constructor creates and interns a String corresponding to the field's class signature. By making this process lazy we can achieve a small startup gain on a variety of applications.

The most straightforward way of safely doing this lazily would involve making the final signature field lazy, which could have negative performance implications - but analysis shows that the signature field itself is not read during hot paths in serialization (only during one-off setup steps), so this should have no measurable impact on overall serialization performance.