Java8-Stream-No.01



import java.util.ArrayList;

import java.util.List;

import java.util.Optional;

public class Streams1 {

    public static void main(String[] args) {

        List<String> stringCollection = new ArrayList<>();

        stringCollection.add("ddd2");

        stringCollection.add("aaa2");

        stringCollection.add("bbb1");

        stringCollection.add("aaa1");

        stringCollection.add("bbb3");

        stringCollection.add("ccc");

        stringCollection.add("bbb2");

        stringCollection.add("ddd1");

        // filtering

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

        // "aaa2", "aaa1"

        // sorting

        stringCollection

                .stream()

                .sorted()

                .filter((s) -> s.startsWith("a"))

                .forEach(System.out::println);

        // "aaa1", "aaa2"

        // mapping

        stringCollection

                .stream()

                .map(String::toUpperCase)

                .sorted((a, b) -> b.compareTo(a))

                .forEach(System.out::println);

        // "DDD2", "DDD1", "CCC", "BBB3", "BBB2", "AAA2", "AAA1"

        // matching

        boolean anyStartsWithA = stringCollection

                .stream()

                .anyMatch((s) -> s.startsWith("a"));

        System.out.println(anyStartsWithA);      // true

        boolean allStartsWithA = stringCollection

                .stream()

                .allMatch((s) -> s.startsWith("a"));

        System.out.println(allStartsWithA);      // false

        boolean noneStartsWithZ = stringCollection

                .stream()

                .noneMatch((s) -> s.startsWith("z"));

        System.out.println(noneStartsWithZ);      // true

        // counting

        long startsWithB = stringCollection

                .stream()

                .filter((s) -> s.startsWith("b"))

                .count();

        System.out.println(startsWithB);    // 3

        // reducing

        Optional<String> reduced =

                stringCollection

                        .stream()

                        .sorted()

                        .reduce((s1, s2) -> s1 + "#" + s2);

        reduced.ifPresent(System.out::println);

        // "aaa1#aaa2#bbb1#bbb2#bbb3#ccc#ddd1#ddd2"

    }

}
巴特西

Java8-Stream-No.01

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