avoid unnecessary object creation

Minimize object allocation in performance-critical code paths by reusing existing objects, caching expensive operations, and choosing efficient alternatives to object creation patterns.

Key strategies include:

1. Reuse existing objects instead of creating new ones: When possible, duplicate or reuse existing objects rather than instantiating new ones. For example, use partition.duplicate() instead of creating a new AlterShareGroupOffsetsResponsePartition.

2. Avoid Optional creation in hotspots: In performance-critical paths, use direct null checks instead of Optional.ofNullable(). Replace:

   Optional.ofNullable(image.cluster().broker(brokerId)).ifPresent(b -> {
    // process broker
   });
   

   With:

   var broker = image.cluster().broker(brokerId);
   if (broker != null && !broker.fenced() && broker.listeners().containsKey(listenerName.value())) {
    res.add(brokerId);
   }
   

3. Cache expensive operations outside loops: When performing expensive operations like Errors.forException() that scan lists, compute the result once and reuse it rather than calling it repeatedly in loops.

4. Choose efficient collection operations: Use Collections.unmodifiableSet() instead of Set.copyOf() to avoid deep copying, and prefer direct collection operations over creating intermediate temporary collections.

5. Optimize conditional checks: Order conditional checks to perform cheaper operations first, such as checking partitionInfo.leader() == null before creating a TopicPartition object.

This approach is particularly important in frequently executed code paths, request processing hotspots, and tight loops where object allocation overhead can significantly impact performance.