java8 stream操作:从集合中获取符合条件的元素

List students = new ArrayList<>();

students.add(new Student(1,"张三",11));
students.add(new Student(2,"李四",11));
students.add(new Student(3,"王五",13));
students.add(new Student(4,"赵六",14));

int studentId = 1;
Student student = students.stream().filter(o -> o.getId() == studentId).findAny().orElse(null);

如上，获取id为1的元素对象，如果不存在返回null。

获取11岁年纪的学生，如下：

int ageNum = 11;
List stuList = students.stream().filter(o -> o.getAge() == ageNum ).collect(Collectors.toList());

获取学生姓名集合，如下：

List names = students.stream().map(Student::getName()).collect(Collectors.toList()).stream().distinct().collect(Collectors.toList());

student类：

public class Student {

    private int id;
    private String name;
    private int age;

    public Student(int id, String name, int age) {
        this.id = id;
        this.name = name;
        this.age= age;
    }
get...
set...
}