public class Student {

    private String name;

    private int age;

    public String getName() {

        return name;

    }

    public Student setName(String name) {

        this.name = name;

        return this;

    }

    public int getAge() {

        return age;

    }

    public Student setAge(int age) {

        this.age = age;

        return this;

    }

    @Override

    public String toString() {

        return "Student{" +

                "name='" + name + '\'' +

                ", age=" + age +

                '}';

    }

}

public class Test {

    public static void main(String[] args) {

        List<Student> list = new ArrayList<>();

        for (int i = 0; i < 4; i++) {

            list.add(new Student().setAge(i + 10).setName("yiqq" + i));

        }

        //直接返回对象

        Student student = list.stream().filter(a -> "yiqq0".equals(a.getName())).findFirst().orElse(null);

        System.out.println(student);

        //返回Optional

        Optional<Student> firstA = list.stream().filter(a -> "yiqq0".equals(a.getName())).findFirst();

        Student stu = firstA.orElse(null);

        System.out.println(stu);

        //获取对象

        if (firstA.isPresent()) {

            Student stus = firstA.get();

            System.out.println(stus);

        }

        //返回集合

        List<Student> studentList = list.stream().filter(a -> "yiqq0".equals(a.getName())).collect(Collectors.toList());

        System.out.println(studentList);

        //取对象中所有的id的集合

        List<Integer> integerList = list.stream().map(Student::getAge).distinct().collect(Collectors.toList());//distinct去重

        System.out.println(integerList);

    }

}

public class TestL {

    public static void main(String[] args) {

        String[] atp = {"00006", "00002","00001","00005","00004", "00003"};

        Arrays.sort(atp, new Comparator<String>() {

            @Override

            public int compare(String s1, String s2) {

                return (s1.compareTo(s2));

            }

        });

        Arrays.sort(atp, (String s1, String s2) -> (s1.compareTo(s2)));//Lambdas排序集合

        List<String> players =  Arrays.asList(atp);//数组转list集合

        String [] array = players.toArray(new String[0]);//list集合转数组

        System.out.println(Arrays.toString(array));//数组转化为string输出

        // 以前的循环方式

        for (String player : players) {

            System.out.print(player + "; ");

        }

        // 使用 lambda 表达式以及函数操作(functional operation)

        players.forEach((player) -> System.out.print(player + "; "));

        // 在 Java 8 中使用双冒号操作符(double colon operator)

        players.forEach(System.out::println);

    }

}