Java8 Stream實例--統計出所有含‘張’字的人員的平均年齡

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("張")>=0)
            .mapToDouble(s->s.getAge())
            .average()
            .getAsDouble();
        System.out.println("包含張字的所有人的平均年齡為："+ 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("張三",16,Student.Sex.MALE);
        Student s2 = new Student("張四",18,Student.Sex.FEMALE);
        Student s3 = new Student("王五",26,Student.Sex.MALE);
        Student s4 = new Student("趙柳",36,Student.Sex.FEMALE);
        List<Student> ss = new ArrayList<Student>();
        ss.add(s1);
        ss.add(s2);
        ss.add(s3);
        ss.add(s4);
        return ss;
    }
}