Java8 Stream的几种生成方式

Stream是Java8的重要特性之一。那么生成Stream的方式有哪些？ 1， 通过Collections类，2，通过静态方法，例如IntStream.range，Files.walk方法等， 3，借助Java.util.Spliterator，有关stream的更详细内容后面会介绍，这里只是简单给出生成stream的例子。

下面通过代码示例一一展示。

第一种，通过Collections类

        List<String> stringCollection = new ArrayList<>();
        stringCollection.add("ddd2");
        stringCollection.add("aaa2");
        stringCollection.add("bbb1");
        stringCollection.add("aaa1");
        stringCollection.add("bbb3");
        stringCollection.add("ccc4");
        stringCollection.add("bbb2");
        stringCollection.add("ddd1");

        stringCollection
.stream()
.filter((s) -> s.startsWith("a"))
.forEach(System.out::println);

第二种，通过静态方法

import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.stream.Stream;
import java.io.IOException;

public class FilesWalk {
    public static void main(String[] args) {
        final Path path = Paths.get("C:\\Afolder");
        int maxDepth = 5;
        try( Stream<Path> entries = Files.walk(path, maxDepth) ) {
            entries.onClose( () -> System.out.println("Done!") ).forEach(
                p -> {
                         System.out.println(p.toFile().getAbsolutePath());
                    } 
                );
        }
        catch (IOException e) {
            e.printStackTrace();
        }
    }
}

第三种，借助java.util.Spliterator;

import java.util.ArrayList;
import java.util.Spliterator;
import java.util.stream.StreamSupport;
import java.util.stream.Stream;

public class SpliteratorDemo {

    public static void main(String[] args) {
        ArrayList<Integer> number_List = new ArrayList<>(); 
        Spliterator<Integer> mySpliterator, myParallelSpliterator;

        number_List.add(1);
        number_List.add(2);
        number_List.add(3);
        number_List.add(4);
        number_List.add(5);

        mySpliterator = number_List.spliterator();
        myParallelSpliterator = number_List.spliterator();

        System.out.println("Characteristics Of Spliterator are : "+mySpliterator.characteristics());
        System.out.println("estimateSize Of Spliterator is : "+mySpliterator.estimateSize());

        Stream<Integer> intStream = StreamSupport.stream(mySpliterator.trySplit(), false);
        Stream<Integer> intStream2 = StreamSupport.stream(mySpliterator.trySplit(), false);
        Stream<Integer> intStream3 = StreamSupport.stream(mySpliterator.trySplit(), false);
        //Stream<Integer> intStream4 = StreamSupport.stream(mySpliterator.trySplit(), false);
        Stream<Integer> intStream4 = StreamSupport.stream(myParallelSpliterator.trySplit(), true);
        System.out.println("All elements");
        intStream
.filter((p) -> (p < 9))
.forEach(System.out::println);

        System.out.println("All elements");
        intStream2
.forEach(System.out::println);

        System.out.println("All elements");
        intStream3
.forEach(System.out::println);

        System.out.println("All elements");
        intStream4
.forEach(System.out::println);
    }
}