
Java 函数式编程 - 并行执行
并行执行是函数式编程的一个关键概念,它通过把大任务分解成更小的独立任务来完成,然后以并行方式完成这些小任务,最后将结果合并在一起得到完整的结果。随着多核处理器的出现,此技术有助于更快地执行代码。Java 有基于线程的编程支持以实现并行处理,但它比较难学,而且不借助错误很难实现。从 Java 8 起,流有 parallel 方法,集合有 parallelStream() 方法,可并行完成任务。请看以下示例
import java.util.ArrayList; import java.util.Arrays; import java.util.List; public class FunctionTester { public static void main(String[] args) { Integer[] intArray = {1, 2, 3, 4, 5, 6, 7, 8 }; List<Integer> listOfIntegers = new ArrayList<>(Arrays.asList(intArray)); System.out.println("List using Serial Stream:"); listOfIntegers .stream() .forEach(e -> System.out.print(e + " ")); System.out.println(""); System.out.println("List using Parallel Stream:"); listOfIntegers .parallelStream() .forEach(e -> System.out.print(e + " ")); System.out.println(""); System.out.println("List using Another Parallel Stream:"); listOfIntegers .stream() .parallel() .forEach(e -> System.out.print(e + " ")); System.out.println(""); System.out.println("List using Parallel Stream but Ordered:"); listOfIntegers .parallelStream() .forEachOrdered(e -> System.out.print(e + " ")); System.out.println(""); } }
输出
List using Serial Stream: 1 2 3 4 5 6 7 8 List using Parallel Stream: 6 5 8 7 3 4 2 1 List using Another Parallel Stream: 6 2 1 7 4 3 8 5 List using Parallel Stream but Ordered: 1 2 3 4 5 6 7 8
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