상태패턴 1부 패턴소개

package me.whiteship.designpatterns._03_behavioral_patterns._20_state._01_before;

public class Client {

    public static void main(String[] args) {
        Student student = new Student("whiteship");
        OnlineCourse onlineCourse = new OnlineCourse();

        Student keesun = new Student("keesun");
        keesun.addPrivateCourse(onlineCourse);

        onlineCourse.addStudent(student);
        onlineCourse.changeState(OnlineCourse.State.PRIVATE);

        onlineCourse.addStudent(keesun);

        onlineCourse.addReview("hello", student);

        System.out.println(onlineCourse.getState());
        System.out.println(onlineCourse.getStudents());
        System.out.println(onlineCourse.getReviews());
    }
}

package me.whiteship.designpatterns._03_behavioral_patterns._20_state._01_before;

import java.util.ArrayList;
import java.util.List;

public class OnlineCourse {

    public enum State {
        DRAFT, PUBLISHED, PRIVATE
    }

    private State state = State.DRAFT;

    private List<String> reviews = new ArrayList<>();

    private List<Student> students = new ArrayList<>();

    public void addReview(String review, Student student) {
        if (this.state == State.PUBLISHED) {
            this.reviews.add(review);
        } else if (this.state == State.PRIVATE && this.students.contains(student)) {
            this.reviews.add(review);
        } else {
            throw new UnsupportedOperationException("리뷰를 작성할 수 없습니다.");
        }
    }

    public void addStudent(Student student) {
        if (this.state == State.DRAFT || this.state == State.PUBLISHED) {
            this.students.add(student);
        } else if (this.state == State.PRIVATE && availableTo(student)) {
            this.students.add(student);
        } else {
            throw new UnsupportedOperationException("학생을 해당 수업에 추가할 수 없습니다.");
        }

        if (this.students.size() > 1) {// 두명이상인 경우 private 상태가 된다고 가정
            this.state = State.PRIVATE;
        }
    }

    public void changeState(State newState) {
        this.state = newState;
    }

    public State getState() {
        return state;
    }

    public List<String> getReviews() {
        return reviews;
    }

    public List<Student> getStudents() {
        return students;
    }

    private boolean availableTo(Student student) {
        return student.isEnabledForPrivateClass(this);
    }

}

package me.whiteship.designpatterns._03_behavioral_patterns._20_state._01_before;

import java.util.ArrayList;
import java.util.List;

public class Student {

    private String name;

    public Student(String name) {
        this.name = name;
    }

    private List<OnlineCourse> privateCourses = new ArrayList<>();

    public boolean isEnabledForPrivateClass(OnlineCourse onlineCourse) {
        return privateCourses.contains(onlineCourse);
    }

    public void addPrivateCourse(OnlineCourse onlineCourse) {
        this.privateCourses.add(onlineCourse);
    }

    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                '}';
    }
}