Get last element of Stream/List in a one-liner
To get the last element of a List by converting it to a Stream and using reduce((a, b) -> b):
This code conveniently wraps the last element in an Optional<T> to avoid NullPointerExceptions when dealing with empty lists.
And if you are a Google Guava user:
Precautions with infinite streams
If your stream is a never-ending party, trying to get the last guest isn't going to end well. Always check your Stream party has a definitive end time, else, you'll be stuck getting the last party-goer forever.
Priority: Performance vs simplicity
The simplicity of reduce() is enticing, but beware—it might fancy a slow dance, given its linear time complexity. For larger guest lists or when performance is top-priority, Streams.findLast() by Google Guava should be your +1 — it's a quicker dancer with logarithmic to linear time complexity.
Addressing void: Handling empty lists
Uh oh, your guest list was empty, and you didn't know until you tried greeting the last arrival. To avoid embarrassment — or, rather, NoSuchElementException — always check for party-goers before trying to find the last guest:
Zen of Reduction
Working with reduce()? Make sure the accumulator function is stateless and associative to avoid any dance-offs - inaccurate results or slower performance, especially when your conga line moves in parallel.
Order of the conga line: Ordered vs unordered streams
When using reduce(), the sequence of the conga line matters; for ordered streams, you'll find the last dancer, but if the line is unordered, it's anyone's game — this is findAny() in disguise!
For the experts: Special Tips
Custom Dance: Custom Collecting
Want to choreograph your own dance routine? You can create a custom Collector to define your moves for finding the last dancer. May seem over-the-top, but hey, going the extra mile often pays off in learning.
Stay in Rhythm: Avoid Expensive Operations
Don't try to rearrange the entire conga line just to find the last dancer— you'll exhaust everyone! Sorting the whole stream is a big no-no.
If it's a Queue or Deque
When working with a Queue or Deque, use their built-in methods like peek() or getLast(). These dancers know their routines well - they get you the last element really quick!
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