lambda表达式的一些学习

关于lambda表达式的一些学习，例举出来。

1.学生实体类

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 +
                '}';
    }
}

2.操作对象有关的方法

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);
    }
}

3.lambda表达式的一些用法

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);
    }
}