java基础——常用聚合操作

朱雀 2023-06-30 08:48 20阅读 0赞

package lambda;
    
    import character.Hero;
    
    import java.util.ArrayList;
    import java.util.Arrays;
    import java.util.List;
    import java.util.Random;
    
    public class TestAggregate { 
        public static void main(String[] args){ 
            Random r = new Random();
            List<Hero> heros = new ArrayList<>();
            for(int i=0;i<8;i++){ 
                heros.add(new Hero("hero-"+i,r.nextInt(200),r.nextInt(100)));
            }
            heros.add(heros.get(0));
            System.out.println("初始化的集合：");
            System.out.println(heros);
    
            System.out.println("hp>100&&damage<50的集合：");
            heros
                    .stream()
                    .filter(h->h.hp>100&&h.damage<50)
                    .forEach(h->System.out.println(h));
    
            System.out.println("去除重复数据：");
            heros
                    .stream()
                    .distinct()
                    .forEach(h->System.out.println(h));
    
            System.out.println("按照血量大小排序：");
            heros
                    .stream()
                    .sorted((h1,h2)->h1.hp>h2.hp?1:-1)
                    .forEach(h->System.out.println(h));
    
            System.out.println("保留前三个:");
            heros.stream()
                    .limit(3)
                    .forEach(h->System.out.println(h));
    
            System.out.println("忽略前三个：");
            heros
                    .stream()
                    .skip(3)
                    .forEach(h->System.out.println(h));
    
            System.out.println("转换为double的Stream：");
            heros
                    .stream()
                    .mapToDouble(Hero::getHp)
                    .forEach(h->System.out.println(h));
    
            System.out.println("转换为任意类型的stream：");
            heros
                    .stream()
                    .map((h)->h.name+" - "+h.hp+" - "+h.damage)
                    .forEach(h->System.out.println(h));
    
            System.out.println("返回一个数组：");
            Object[] hs = heros
                    .stream()
                    .toArray();
            System.out.println(Arrays.toString(hs));
    
            System.out.println("返回伤害最低的：");
            Hero minHero = heros
                    .stream()
                    .min((h1,h2)->h1.damage-h2.damage)
                    .get();
            System.out.println(minHero);
    
            System.out.println("返回伤害最高的：");
            Hero maxHero = heros
                    .stream()
                    .max((h1,h2)->h1.damage-h2.damage)
                    .get();
            System.out.println(maxHero);
    
            System.out.println("流中的个数：");
            long count = heros
                    .stream()
                    .count();
            System.out.println(count);
    
            System.out.println("第一个英雄：");
            Hero first = heros
                    .stream()
                    .findFirst()
                    .get();
            System.out.println(first);
    
            Hero h = heros
                    .stream()
                    .sorted((h1,h2)->h1.hp>h2.hp?-1:1)
                    .skip(2)
                    .findFirst()
                    .get();
            System.out.println("血量第三高："+h);
    
        }
    }