package com.company;

import java.util.ArrayList;

import java.util.List;

import java.util.Optional;

import java.util.function.Predicate;

import java.util.stream.Stream;

public class Main {

    public static void main(String[] args) {

        learnStream();

    }

    public static void emptyLine(){System.out.println();System.out.println();}

    public static void learnStream() {

        ////首先,创建一个1-6乱序的List

        List<Integer> lists = new ArrayList<>();

        lists.add(4);

        lists.add(3);

        lists.add(6);

        lists.add(1);

        lists.add(5);

        lists.add(2);

        //遍历list

        System.out.print("lists数据：");

        for (Integer elem : lists) {

            System.out.print(elem + ",");

        }

        emptyLine();

        //获取list中的最小值

        System.out.print("list中的最小值：");

        Stream<Integer> stream = lists.stream();

        Optional<Integer> min = stream.min(Integer::compareTo);

        if (min.isPresent()) {

            System.out.println(min.get());

        }

        emptyLine();

        //获取list中的最大值

        System.out.print("list中的最大值：");

        lists.stream().max(Integer::compareTo).ifPresent(System.out::println);

        emptyLine();

        //排序

        System.out.print("排序：");

        Stream<Integer> sorted = lists.stream().sorted();

        sorted.forEach(elem -> System.out.print(elem + ","));

        emptyLine();

        //过滤

        System.out.print("过滤list，只留下大于3的元素：");

        lists.stream().filter(elem -> elem > 3).forEach(elem -> System.out.print(elem + ","));

        emptyLine();

        //过滤

        System.out.print("过滤list，只留下大于0并且小于4的元素：");

        lists.stream().filter(elem -> elem > 0).filter(elem -> elem < 4).forEach(elem -> System.out.print(elem + ","));

        emptyLine();

        System.out.print("过滤list，只留下大于0并且小于4的元素,并排序：");

        lists.stream().filter(elem -> elem > 0).filter(elem -> elem < 4).sorted(Integer::compareTo).forEach(elem -> System.out.print(elem + ","));

        emptyLine();

        //自定义过滤

        Predicate<Integer> elme1 =(param) -> (param>0);

        Predicate<Integer> elme2 =(param) -> (param<4);

        System.out.print("过滤list，只留下大于0并且小于4的元素,并排序：(使用自定义过滤)");

        lists.stream().filter(elme1).filter(elme2).sorted(Integer::compareTo).forEach(elem -> System.out.print(elem + ","));

        emptyLine();

        //经过了前面的这么多流操作,我们再来看看List里面的值有没有发生什么改变

        //遍历list

        System.out.print("原来lists数据：");

        for (Integer elem : lists) {

            System.out.print(elem + ",");

        }

    }

}