list.stream的常见使用

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 filter
	List<Student> l1 = list.stream().filter(student -> student.sex.equals("男")).collect(toList());
	
	//map的key值true为男，false为女的集合
	Map<Boolean, List<Student>> map = list.stream().collect(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> map = 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(toList());

	//求所有人的平均年龄
	double avg = list.stream().collect(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(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(toList());

	//求年龄最小的两个学生
	List<Student> l4 = l3.stream().limit(2).collect(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());
}