在java中创建自定义收集器

import java.util.stream.Collector;
import java.util.stream.Collectors;

public class CustomCollectorDemo {

    public static void main(String[] args) {
        double average = Stream.of(1, 2, 3, 4, 5)
                .collect(averageCollector());

        System.out.println("Average: " + average);
    }

    public static Collector<Integer, AverageAccumulator, Double> averageCollector() {
        return Collector.of(
                AverageAccumulator::new,
                AverageAccumulator::add,
                AverageAccumulator::combine,
                AverageAccumulator::average
        );
    }

    static class AverageAccumulator {
        private int sum;
        private int count;

        public void add(int value) {
            sum += value;
            count++;
        }

        public AverageAccumulator combine(AverageAccumulator other) {
            sum += other.sum;
            count += other.count;
            return this;
        }

        public double average() {
            return (double) sum / count;
        }
    }
}