StreamTest.java

package com.bootdo.test;

import java.util.Comparator;
import java.util.IntSummaryStatistics;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

import com.google.common.collect.Lists;

public class StreamTest {

	public static void main(String[] args) {
        List<Student> list = Lists.newArrayList();
        list.add(new Student("测试", "男", 18));
        list.add(new Student("开发", "男", 20));
        list.add(new Student("运维", "女", 19));
        list.add(new Student("DBA", "女", 22));
        list.add(new Student("运营", "男", 24));
        list.add(new Student("产品", "女", 21));
        list.add(new Student("经理", "女", 25));
        list.add(new Student("产品", "女", 21));
 
        //求性别为男的学生集合
        List<Student> l1 = list.stream().filter(student -> student.sex.equals("男")).collect(Collectors.toList());
        
        //map的key值true为男，false为女的集合
        Map<Boolean, List<Student>> map = list.stream().collect(Collectors.partitioningBy(student -> student.getSex().equals("男")));
 
        //求性别为男的学生总岁数
        Integer sum = list.stream().filter(student -> student.sex.equals("男")).mapToInt(Student::getAge).sum();
 
        //按性别进行分组统计人数
        Map<String, Integer> map9 = list.stream().collect(Collectors.groupingBy(Student::getSex, Collectors.summingInt(p -> 1)));
 
        //判断是否有年龄大于25岁的学生
        boolean check = list.stream().anyMatch(student -> student.getAge() > 25);
 
        //获取所有学生的姓名集合
        List<String> l2 = list.stream().map(Student::getName).collect(Collectors.toList());
 
        //求所有人的平均年龄
        double avg = list.stream().collect(Collectors.averagingInt(Student::getAge));

        //求年龄最大的学生
        Student s = list.stream().reduce((student, student2) -> student.getAge() > student2.getAge() ? student:student2).get();
        
        Student stu = list.stream().collect(Collectors.maxBy(Comparator.comparing(Student::getAge))).get();
 
        //按照年龄从小到大排序
        List<Student> l3 = list.stream().sorted((s1, s2) -> s1.getAge().compareTo(s2.getAge())).collect(Collectors.toList());
 
        //求年龄最小的两个学生
        List<Student> l4 = l3.stream().limit(2).collect(Collectors.toList());
 
        //获取所有的名字，组成一条语句
        String str = list.stream().map(Student::getName).collect(Collectors.joining(",", "[", "]"));
        
        //获取年龄的最大值、最小值、平均值、求和等等
        IntSummaryStatistics intSummaryStatistics = list.stream().mapToInt(Student::getAge).summaryStatistics();
        System.out.println(intSummaryStatistics.getMax());
        System.out.println(intSummaryStatistics.getCount());
    }
 
 
}


class Student{
    String name;
    String sex;
    Integer age;
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getSex() {
		return sex;
	}
	public void setSex(String sex) {
		this.sex = sex;
	}
	public Integer getAge() {
		return age;
	}
	public void setAge(Integer age) {
		this.age = age;
	}
	public Student(String name, String sex, Integer age) {
		super();
		this.name = name;
		this.sex = sex;
		this.age = age;
	}
    
    
}