design patterns : state

design-pattern/gof/src/state/after/Client.java

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+package state.after;
+
+public class Client {
+
+    public static void main(String[] args) {
+        OnlineCourse onlineCourse = new OnlineCourse();
+        Student kim = new Student("kim");
+
+        onlineCourse.addStudent(kim);
+        onlineCourse.addReview("hello", kim);
+
+        onlineCourse.changeState(new Private(onlineCourse));
+        onlineCourse.addReview("hello", kim);
+
+        Student lee = new Student("lee");
+        onlineCourse.addStudent(lee);
+
+        lee.addPrivate(onlineCourse);
+        onlineCourse.addStudent(lee);
+
+        System.out.println(onlineCourse);
+    }
+}

design-pattern/gof/src/state/after/Draft.java

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+package state.after;
+
+public class Draft implements State {
+
+    private OnlineCourse onlineCourse;
+
+    public Draft(OnlineCourse onlineCourse) {
+        this.onlineCourse = onlineCourse;
+    }
+
+    @Override
+    public void addReview(String review, Student student) {
+        System.out.println("드래프트 상태에서는 리뷰를 남길 수 없습니다.");
+//        throw new UnsupportedOperationException("드래프트 상태에서는 리뷰를 남길 수 없습니다.");
+    }
+
+    @Override
+    public void addStudent(Student student) {
+        this.onlineCourse.getStudents().add(student);
+        if (this.onlineCourse.getStudents().size() > 1) {
+            this.onlineCourse.changeState(new Private(this.onlineCourse));
+        }
+    }
+}

design-pattern/gof/src/state/after/OnlineCourse.java

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+package state.after;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class OnlineCourse {
+
+    private State state = new Draft(this);
+
+    private List<Student> students = new ArrayList<>();
+
+    private List<String> reviews = new ArrayList<>();
+
+    public void addStudent(Student student) {
+        this.state.addStudent(student);
+    }
+
+    public void addReview(String review, Student student) {
+        this.state.addReview(review, student);
+    }
+
+    public State getState() {
+        return state;
+    }
+
+    public List<Student> getStudents() {
+        return students;
+    }
+
+    public List<String> getReviews() {
+        return reviews;
+    }
+
+    public void changeState(State state) {
+        this.state = state;
+    }
+
+    @Override
+    public String toString() {
+        return "OnlineCourse{" +
+                "state=" + state +
+                ", students=" + students +
+                ", reviews=" + reviews +
+                '}';
+    }
+
+}

design-pattern/gof/src/state/after/Private.java

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+package state.after;
+
+public class Private implements State {
+
+    private OnlineCourse onlineCourse;
+
+    public Private(OnlineCourse onlineCourse) {
+        this.onlineCourse = onlineCourse;
+    }
+
+    @Override
+    public void addReview(String review, Student student) {
+        if (this.onlineCourse.getStudents().contains(student)) {
+            this.onlineCourse.getReviews().add(review);
+        } else {
+            System.out.println("프라이빗 코스를 수강하는 학생만 리뷰를 남길 수 있습니다.");
+//            throw new UnsupportedOperationException("프라이빗 코스를 수강하는 학생만 리뷰를 남길 수 있습니다.");
+        }
+    }
+
+    @Override
+    public void addStudent(Student student) {
+        if (student.isAvailable(this.onlineCourse)) {
+            this.onlineCourse.getStudents().add(student);
+        } else {
+            System.out.println("프라이빗 코스를 수강할 수 없습니다.");
+//            throw new UnsupportedOperationException("프라이빗 코스를 수강할 수 없습니다.");
+        }
+    }
+}

design-pattern/gof/src/state/after/Published.java

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+package state.after;
+
+public class Published implements State {
+
+    private OnlineCourse onlineCourse;
+
+    public Published(OnlineCourse onlineCourse) {
+        this.onlineCourse = onlineCourse;
+    }
+
+    @Override
+    public void addReview(String review, Student student) {
+        this.onlineCourse.getReviews().add(review);
+    }
+
+    @Override
+    public void addStudent(Student student) {
+        this.onlineCourse.getStudents().add(student);
+    }
+}

design-pattern/gof/src/state/after/State.java

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+package state.after;
+
+public interface State {
+
+    void addReview(String review, Student student);
+
+    void addStudent(Student student);
+}

design-pattern/gof/src/state/after/Student.java

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+package state.after;
+
+import java.util.HashSet;
+import java.util.Set;
+
+public class Student {
+
+    private String name;
+
+    public Student(String name) {
+        this.name = name;
+    }
+
+    private Set<OnlineCourse> onlineCourses = new HashSet<>();
+
+    public boolean isAvailable(OnlineCourse onlineCourse) {
+        return this.onlineCourses.contains(onlineCourse);
+    }
+
+    public void addPrivate(OnlineCourse onlineCourse) {
+        this.onlineCourses.add(onlineCourse);
+    }
+
+    @Override
+    public String toString() {
+        return "Student{" +
+                "name='" + name + '\'' +
+                '}';
+    }
+}

design-pattern/gof/src/state/before/Client.java

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+package state.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());
+    }
+}

design-pattern/gof/src/state/before/OnlineCourse.java

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+package state.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) {
+            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);
+    }
+
+
+}

design-pattern/gof/src/state/before/Student.java

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+package state.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 + '\'' +
+                '}';
+    }
+}