java8——stream

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package stream;

import com.sun.imageio.plugins.common.InputStreamAdapter;

import java.util.*;
import java.util.stream.Collectors;

/**
 * @author: wu linchun
 * @time: 2021/7/26 14:19
 * @description: java8 stream
 */

public class Java8Test {
    public static void main(String[] args) {
        //filter
        //初始化一个filter_list
        List<String> filter_list = Arrays.asList("123", "234", "ssa", "ccd", "hhh", "", "");
        //遍历输出filter_list
        filter_list.forEach(System.out::println);
        //过滤调filter_list中的某些值(过滤掉hhh和ccd)
        List<String> filter = filter_list.stream().filter(String -> !String.equals("hhh") && !String.equals("ccd")).collect(Collectors.toList());
        filter.forEach(System.out::println);

        //map
        List<Integer> map_list1 = Arrays.asList(1, 2, 2, 4, 5, 6);
        //给map_list1中所有值*2
        List<Integer> maplist = map_list1.stream().map(i -> i * 2).collect(Collectors.toList());
        //给map_list1中所有值*2并过滤掉重复值
        List<Integer> mapdistinctlist = map_list1.stream().map(i -> i * 2).distinct().collect(Collectors.toList());
        maplist.forEach(System.out::println);
        mapdistinctlist.forEach(System.out::println);

        //limit
        Random random = new Random();
        //生成随机数并只遍历输出10个
        random.ints().limit(10).forEach(System.out::println);
        List<Integer> limit_list1 = Arrays.asList(1, 10, 2, 4, 5, 6);
        //只取limit_list2的前三个并对这两个数进行升序排序(先取前3个值再对这3个排序）
        List<Integer> limit_list2 = limit_list1.stream().limit(3).sorted().collect(Collectors.toList());
        //先对limit_list2_1升序排序，再取前三个
        List<Integer> limit_list2_1 = limit_list1.stream().sorted().limit(3).collect(Collectors.toList());
        //用自己定义的比较器进行排序
        List<Integer> limit_list3 = limit_list1.stream().sorted(new MyComparetor()).collect(Collectors.toList());
        List<String> limit_list4 = Arrays.asList("a223", "tsr", "bdd", "cdd", "caa", "a122");
        List<String> limit_list5 = limit_list4.stream().sorted(new MyComparetor1()).collect(Collectors.toList());
        limit_list2.forEach(System.out::println);
        limit_list2_1.forEach(System.out::println);
        limit_list3.forEach(System.out::println);
        limit_list5.forEach(System.out::println);

        //sorted
        Random random1 = new Random();
        random1.ints().limit(10).sorted().forEach(System.out::println);

    }

    static class MyComparetor implements Comparator<Integer> {

        @Override
        public int compare(Integer o1, Integer o2) {
            //升序：o1-o2
            //降序：o2-o1
            return o1 - o2;
        }
    }

    static class MyComparetor1 implements Comparator<String> {

        @Override
        public int compare(String o1, String o2) {
            //升序：o1.compareTo(o2)
            //降序：o2.compareTo(o1)
            return o1.compareTo(o2);
        }
    }
}

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