.toarray(new MyClass
In the world of Java Collections, the syntax .toArray(new MyClass[0]) takes the throne for performance and simplicity when converting a collection to an array. It leverages the power of JVM optimizations. Habits die hard, and while .toArray(new MyClass[myList.size()]) had its heyday, with the improvements in the more recent Java versions, it no longer provides a significant performance benefit.
And that kids, is how I met your array. Now for the longer version of the story.
A peek into JVM optimizations
If we time travel to the ancient age of Java, you'd find new MyClass[myList.size()] as the norm. Times change and so do JVM optimizations. When you pass an empty array to the toArray method, the JIT compiler, like the magical entity it is, makes an educated decision about the best time and way to resize the array.
The JVM science behind the speedy resize is an intrinsic size computation which is snappier than the reflective method used when we pass a presized array of myList.size().
Performance meets explicitness
Who doesn’t like a performance boost right? myList.toArray(new MyClass[0]) has your back. It offers a shortcut to bypass implicit casting and encourages the creation of fewer unnecessary objects. This results in a performance improvement and reduced garbage collection strain. Remember, less garbage means a happier environment, even in Java!
The biggest fish in your pond
But hold your horses! You might still find a use for .toArray(new MyClass[myList.size()]) for some specific scenarios. If you encounter a large list and almost every nanosecond matters, whipping out a JMH (Java Microbenchmark Harness) microbenchmark might answer your questions better. Sometimes reusing the existing array, only when the size fits like a glove, could lead to different performance characteristics due to the magic of array initialization.
Code aesthetics and synchronicity
For things that are often overlooked when in favour of raw performance, clean and consistent code is a winner. Sticking with the zero-sized array approach keeps your code cohesive and shows trust in the vigilant JVM optimizations.
All about array initialization
When it comes to creating arrays, you have two choices: gamble with new MyClass[0] or play safe with new MyClass[myList.size()].
The former is an adaptive approach. You create an empty array, and leave it to the JVM to figure out when and how to resize it. It's the "go with the flow" style.
The latter method, new MyClass[myList.size()], chooses caution over speed. Here, you're creating an array with a predetermined size.
Both methods have their time and place. But thanks to the modern JIT compilers, the empty array version has recently been outperforming the presized version in a few circumstances.
Harness the power of benchmarking
If you’re reading this, chances are performance is of prime importance to you. Therefore, benchmarking is your best friend. Factors like list size and dynamics, operation types following array creation can alter performance outcomes. So wielding tools like JMH will help you settle on the champion practice for your scenario. Microbenchmarking without it can lead to misleading results.
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