1.2.Java8的流库——流的创建

一切尽在代码中…

package com.example.demo;

import java.io.IOException;
import java.math.BigInteger;
import java.nio.charset.StandardCharsets;
import java.nio.file.*;
import java.util.Iterator;
import java.util.List;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.regex.Pattern;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;




public class CreatingStreams{
    public static  void show(String title,Streamstream){
        final int SIZE = 10;
        List firstElements = stream.limit(SIZE + 1).collect(Collectors.toList());
        System.out.print(title + ":");
        for (int i = 0; i < firstElements.size(); i++) {
            if (i>0){
                System.out.print(",");
            }
            if (i
                System.out.print(firstElements.get(i));
            }
            else {
                System.out.print("...");
            }
            System.out.println();
        }
    }



    public static void main(String[] args) throws IOException {
        Path path = Paths.get("D:\gutenberg\Test.txt");
        //读取该路径文件内容
        String contents = new String(Files.readAllBytes(path), StandardCharsets.UTF_8);
        Stream words = Stream.of(contents.split("\PL+"));
        show("words",words);

        Stream song = Stream.of("gently","down","the","stream");
        show("song",song);

        Stream silence = Stream.empty();
        show("silence",silence);

        Stream echos = Stream.generate(() -> "Echo");
        show("echos",echos);

        Stream randoms = Stream.generate(Math::random);
        show("randoms",randoms);

        BigInteger limit = new BigInteger("10000000");
        Stream integers = Stream.iterate(BigInteger.ONE,n -> n.add(BigInteger.ONE));
        show("integers",integers);

        Stream wordsAnotherWay = Pattern.compile("\PL+").splitAsStream(contents);
        show("wordsAnotherWay",wordsAnotherWay);

        try (Stream lines = Files.lines(path, StandardCharsets.UTF_8)){
            show("lines",lines);
        }

        //获取当前电脑磁盘目录
        Iterable iterable = FileSystems.getDefault().getRootDirectories();
        Stream rootDirectories = StreamSupport.stream(iterable.spliterator(), false);
        show("rootDirectories",rootDirectories);

        
        Iterator iterator = Paths.get("/usr/share/dict/words").iterator();
        Stream pathComponents = StreamSupport.stream(Spliterators.spliteratorUnknownSize(iterator, Spliterator.ORDERED), false);
        show("pathComponents",pathComponents);
    }

}

执行结果：

words:qwe
,qwert
,qwertyui
,qwertyuiop
,qwertyuiopa
,qwertyuiopas
song:gently
,down
,the
,stream
silence:echos:Echo
,Echo
,Echo
,Echo
,Echo
,Echo
,Echo
,Echo
,Echo
,Echo
,…
randoms:0.5194703437391313
,0.2760670786937688
,0.9965354224646149
,0.6639623038808492
,0.9339684162587291
,0.6456112697530748
,0.21091642790070342
,0.5188216760030755
,0.3721295912299638
,0.5104006449444084
,…
integers:1
,2
,3
,4
,5
,6
,7
,8
,9
,10
,…
wordsAnotherWay:qwe
,qwert
,qwertyui
,qwertyuiop
,qwertyuiopa
,qwertyuiopas
lines:qwe
,qwert
,qwertyui…
,qwertyuiop qwertyuiopa qwertyuiopas
rootDirectories:C:
,D:
,E:
,F:
pathComponents:usr
,share
,dict
,words