Java8 Stream实例--统计出所有含‘张’字的人员的平均年龄

package com.zhangxueliang.demo;

import java.util.ArrayList;
import java.util.List;
import java.util.stream.Stream;

public class Lambda_Stream_Demo {
    public static void main(String[] args){
        //method1();
        List<Student> list = createStudent();
        double d = list.stream()
            .filter(s->s.getName().indexOf("张")>=0)
            .mapToDouble(s->s.getAge())
            .average()
            .getAsDouble();
        System.out.println("包含张字的所有人的平均年龄为："+ d);
    }
    private static void method1() {
        List<Student> list = createStudent();
        Stream<Student> stream = list.stream();
        stream.filter(s->s.getGender()==Student.Sex.FEMALE).forEach(s->System.out.println(s.toString()));
    }
    public static List<Student> createStudent(){
        Student s1 = new Student("张三",16,Student.Sex.MALE);
        Student s2 = new Student("张四",18,Student.Sex.FEMALE);
        Student s3 = new Student("王五",26,Student.Sex.MALE);
        Student s4 = new Student("赵柳",36,Student.Sex.FEMALE);
        List<Student> ss = new ArrayList<Student>();
        ss.add(s1);
        ss.add(s2);
        ss.add(s3);
        ss.add(s4);
        return ss;
    }
}