Java8通过管道流(stream)来实现集合的一些聚合函数

stream的一些聚合函数包括:
count(), findFirst(), max(), min(), reduce(), sum()

SimpleStreamDemo.java

package corejava8.functional;

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public class SimpleStreamDemo {

	static class Hero {
		String name;
		int age;

		public Hero(String name, int age) {
			this.name = name;
			this.age = age;
		}
	}

	static Hero[] heroes = { 
			new Hero("Grelber", 21), new Hero("Roderick", 12),
			new Hero("Francisco", 35), new Hero("Superman", 65),
			new Hero("Jumbletron", 22), new Hero("Mavericks", 1),
			new Hero("Palladin", 50), new Hero("Athena", 50) };

	public static void main(String[] args) {

		long adultYearsExperience = Arrays.stream(heroes).filter(b -> b.age >= 18)
				.mapToInt(b -> b.age).sum();
		System.out.println("We're in good hands! The adult superheros have "
				+ adultYearsExperience + " years of experience");

		List