How to use parallel streams for concurrent computation in Java?

How to use parallel streams for concurrent calculations in Java? Create parallel streams: Use the Stream.parallel() method. Perform operations: Use parallel streams to perform common operations such as mapping, aggregation, and filtering, applying them in parallel to each element. Parallel Computing: Parallel streams perform operations in parallel, improving performance, especially for large data sets.

How to use parallel streams for concurrent calculations in Java

Introduction

Parallel streams are a powerful tool in Java that allow developers to parallelize computations into multiple threads, thereby improving performance. This article will introduce how to use parallel streams in Java and provide a practical case for you to understand.

Using Parallel Streams

To create parallel streams, you need to use the Stream.parallel() method. This method returns a stream with parallel execution capabilities. The following code snippet demonstrates how to create a parallel stream:

List<Integer> numbers = List.of(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
Stream<Integer> parallelStream = numbers.stream().parallel();

Perform operations using parallel streams

Now that you have created a parallel stream, you can use common stream operations to Perform parallel computations. Here are examples of using parallel streams to perform some common operations:

• Parallel mapping: Apply a function to each element using the map() method.
• Parallel aggregation: Use the reduce() method to combine elements into a single result.
• Parallel filtering: Use the filter() method to filter out elements that do not meet specific conditions.

For example, the following code snippet uses parallel streams to map each number to its square:

List<Integer> squaredNumbers = parallelStream.map(n -> n * n).toList();

You can also use parallel streams to perform more complex parallel calculations. Note that parallel streams do not guarantee operations in a specific order.

Practical Case

Let us understand the powerful function of parallel streaming through a practical case. Consider a scenario where you need to perform complex calculations on the elements of a large list. The following code snippet shows a program that computes the factors of each integer in a list:

List<Integer> numbers = List.of(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);

// 使用串行流计算因子
List<List<Integer>> factors = numbers.stream()
                                    .map(n -> getFactors(n))
                                    .toList();

// 使用并行流计算因子
List<List<Integer>> parallelFactors = numbers.stream()
                                           .parallel()
                                           .map(n -> getFactors(n))
                                           .toList();

In the above example, getFactors() is a method that computes the factors of a given number. By using parallel streams, the program can parallelize calculations to multiple threads, significantly improving performance, especially when the list is large.

Conclusion

Parallel streams are a powerful tool in Java that allow developers to easily parallelize computations, thereby improving performance. You can easily add parallel functionality to your application by using the Stream.parallel() method and common stream operations.

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