10 Java Stream Tips — Must Read
Java Stream API is like a Swiss Army knife for Java developers — it’s versatile, compact, and can handle a wide variety of tasks with ease.
It provides developers with a functional and declarative way to express complex data transformations and operations, making code more concise and expressive.
But with great power comes great responsibility, and using the Stream API effectively requires a solid understanding of best practices and common pitfalls.
Today, we will explore some of the best practices for using Java Stream API and show you how to unleash the full potential of this amazing tool.
Whether you’re a beginner or an experienced developer, you’re sure to learn something new and exciting about using streams in Java
1. Use primitive streams for better performance
When working with primitive types like int, long, and double, use primitive streams like IntStream, LongStream, and DoubleStream instead of streams of boxed types like Integer, Long, and Double. Primitive streams can offer better performance by avoiding the cost of boxing and unboxing.
var array = new int[]{1, 2, 3, 4, 5};
var sum = Arrays.stream(array)
.sum();2. Avoid nesting streams
As a best practice, avoid nesting streams as it can lead to hard-to-read and understand code. Instead, try to break down the problem into smaller pieces and use intermediate collections or local variables to store intermediate results.
var list1 = Arrays.asList("apple", "banana", "cherry");
var list2 = Arrays.asList("orange", "pineapple", "mango");var result = Stream.concat(list1.stream(), list2.stream())
.filter(s -> s.length() > 5)
.collect(Collectors.toList());3. Use parallel streams with caution
Parallel streams can offer better performance when processing large amounts of data, but they can also introduce overhead and race conditions. Use parallel streams with caution and consider factors like the size of the data, the complexity of the operations, and the number of available processors.
var list = Arrays.asList(1, 2, 3, 4, 5);
var sum = list.parallelStream().reduce(0, Integer::sum);4. Use lazy evaluation for better performance
The Stream API supports lazy evaluation, meaning intermediate operations are not executed until a terminal operation is called. As a best practice, try to use lazy evaluation to improve performance by reducing unnecessary computations.
var list = Arrays.asList(1, 2, 3, 4, 5);
var result = list.stream()
.filter(n -> n > 3)
.findFirst();5. Avoid side effects
The Stream API is designed to perform functional operations on data. Avoid introducing side effects like modifying variables outside the stream or performing I/O operations, as this can lead to unpredictable behaviour and reduce code readability.
var list = Arrays.asList("apple", "banana", "cherry");
var count = 0;
list.stream()
.filter(s -> s.startsWith("a"))
.forEach(s -> count++);
Use streams with immutable objects: The Stream API works best with immutable objects. Using immutable objects ensures that the state of the stream is not modified during processing, which can lead to more predictable behavior and better code readability.
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var list = Arrays.asList("apple", "banana", "cherry");
var result = list.stream()
.map(String::toUpperCase)
.collect(Collectors.toList());6. Use streams with immutable objects
The Stream API works best with immutable objects. Using immutable objects ensures that the state of the stream is not modified during processing, which can lead to more predictable behaviour and better code readability
var list = Arrays.asList("apple", "banana", "cherry");
var result = list.stream()
.map(String::toUpperCase)
.collect(Collectors.toList());7. Use filter() before map() to avoid unnecessary processing
If you have a stream that may contain a large number of elements that don’t match your criteria, use filter() before map() to avoid unnecessary processing. This can improve the performance of your code.
var list = Arrays.asList(1, 2, 3, 4, 5);
var filteredList = list.stream()
.filter(i -> i % 2 == 0)
.map(i -> i * 2)
.collect(Collectors.toList());8. Prefer method references over lambda expressions
Method references can make your code more concise and readable than using lambda expressions. If a method reference can be used instead of a lambda expression, prefer it.
var list = Arrays.asList(1, 2, 3, 4, 5);
var sum = list.stream()
.reduce(0, Integer::sum);9. Use distinct() to remove duplicates
If you have a stream that may contain duplicate elements, use the distinct() operation to remove them
var list = Arrays.asList(1, 2, 3, 3, 4, 5, 5);
var distinctList = list.stream()
.distinct()
.collect(Collectors.toList());10. Use sorted() with caution
The sorted() operation can be expensive, especially for large streams. Use it with caution and only when necessary. If you know that the input data is already sorted, you can skip this operation.
var list = Arrays.asList(3, 2, 1);
var sortedList = list.stream()
.sorted()
.collect(Collectors.toList());As I told you earlier, Java Stream API is a powerful and flexible tool that can significantly simplify code for data processing tasks.
By following the tips such as those discussed in this article, you can ensure that your code is both efficient and effective. However, it’s important to remember that using Java Stream API effectively requires a solid understanding of its capabilities and limitations.
So, don’t stop here! Keep learning and exploring the world of Java Stream API to unlock its full potential. And if you have any questions or insights, I encourage you to share them in the comments section below. Let’s continue the conversation and help each other become better Java developers.
