java设计模式精讲 Debug 方式+内存分析 第7章 建造者模式

7-1 建造者模式讲解

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7-2 建造者模式coding

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我们来建造一个视频课程：
首先，创建一个课程类：

public class Course {
    private String courseName;
    private String coursePPT;
    private String courseVideo;
    private String courseArticle;
    /** 问题和答案 */
    private String courseQA;

    public String getCourseName() {
        return courseName;
    }

    public void setCourseName(String courseName) {
        this.courseName = courseName;
    }

    public String getCoursePPT() {
        return coursePPT;
    }

    public void setCoursePPT(String coursePPT) {
        this.coursePPT = coursePPT;
    }

    public String getCourseVideo() {
        return courseVideo;
    }

    public void setCourseVideo(String courseVideo) {
        this.courseVideo = courseVideo;
    }

    public String getCourseArticle() {
        return courseArticle;
    }

    public void setCourseArticle(String courseArticle) {
        this.courseArticle = courseArticle;
    }

    public String getCourseQA() {
        return courseQA;
    }

    public void setCourseQA(String courseQA) {
        this.courseQA = courseQA;
    }

    @Override
    public String toString() {
        return "Course{" +
                "courseName='" + courseName + '\'' +
                ", coursePPT='" + coursePPT + '\'' +
                ", courseVideo='" + courseVideo + '\'' +
                ", courseArticle='" + courseArticle + '\'' +
                ", courseQA='" + courseQA + '\'' +
                '}';
    }
}

我们再来创建一个抽象类：

public abstract class CourseBuilder {

    public abstract void buildCourseName(String courseName);
    public abstract void buildCoursePPT(String coursePPT);
    public abstract void buildCourseVideo(String courseVideo);
    public abstract void buildCourseArticle(String courseArticle);
    public abstract void buildCourseQA(String courseQA);

    public abstract Course makeCourse();
}

我们再来创建一个实现CourseBuilder 的子类：

public class CourseActualBuilder extends CourseBuilder {

    /** 这里把课程组合到实际的Builde当中 */
    private Course course = new Course();

    @Override
    public void buildCourseName(String courseName) {
        course.setCourseName(courseName);
    }

    @Override
    public void buildCoursePPT(String coursePPT) {
        course.setCoursePPT(coursePPT);
    }

    @Override
    public void buildCourseVideo(String courseVideo) {
        course.setCourseVideo(courseVideo);
    }

    @Override
    public void buildCourseArticle(String courseArticle) {
        course.setCourseArticle(courseArticle);
    }

    @Override
    public void buildCourseQA(String courseQA) {
        course.setCourseQA(courseQA);
    }

    @Override
    public Course makeCourse() {
        return course;
    }
}

这里还引入了一个教练类：

public class Coach {
    private CourseBuilder courseBuilder;
    /** 这里的CourseBuilder通过set的方式给注入进来 */
    public void setCourseBuilder(CourseBuilder courseBuilder) {
        this.courseBuilder = courseBuilder;
    }

    public Course makeCourse(String courseName,String coursePPT,
                             String courseVideo,String courseArticle,String courseQA) {
        this.courseBuilder.buildCourseName(courseName);
        this.courseBuilder.buildCoursePPT(coursePPT);
        this.courseBuilder.buildCourseVideo(courseVideo);
        this.courseBuilder.buildCourseArticle(courseArticle);
        this.courseBuilder.buildCourseQA(courseQA);

        return this.courseBuilder.makeCourse();
    }
}

这个就是类图：

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测试：

public class Test {
    public static void main(String[]args){
        /** 利用多态，抽象类的引用指向子类的实现 */
        CourseBuilder courseBuilder = new CourseActualBuilder();
        Coach coach = new Coach();
        /** 这里利用set方法注入进去 */
        coach.setCourseBuilder(courseBuilder);
        Course course = coach.makeCourse("Java设计模式", "Java设计模式PPT", "Java设计模式视频", "Java设计模式手记", "Java设计模式问答");
        System.out.println(course);
    }
}

运行结果：

Course{courseName=‘Java设计模式’, coursePPT=‘Java设计模式PPT’, courseVideo=‘Java设计模式视频’, courseArticle=‘Java设计模式手记’, courseQA=‘Java设计模式问答’}

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我们可以打个断点来看看执行过程：

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我们再来演进一下：使用静态内部类

把具体的实体类和实体类对应的Builder写在一个类里面：

这里一个很关键的地方就是this和静态内部类的使用：

public class Course {
    
    private String courseName;
    private String coursePPT;
    private String courseVideo;
    private String courseArticle;
    /** 问题和答案 */
    private String courseQA;

    public Course(CourseBuilder courseBuilder) {
        this.courseName = courseBuilder.courseName;
        this.coursePPT = courseBuilder.coursePPT;
        this.courseVideo = courseBuilder.courseVideo;
        this.courseArticle = courseBuilder.courseArticle;
        this.courseQA = courseBuilder.courseQA;
    }

    public static class CourseBuilder{
        private String courseName;
        private String coursePPT;
        private String courseVideo;
        private String courseArticle;
        /** 问题和答案 */
        private String courseQA;

        public CourseBuilder builderCourseName(String courseName) {
            this.courseName = courseName;
            return this;
        }
        public CourseBuilder builderCoursePPT(String coursePPT) {
            this.coursePPT = coursePPT;
            return this;
        }
        public CourseBuilder builderCourseVideo(String courseVideo) {
            this.courseVideo = courseVideo;
            return this;
        }
        public CourseBuilder builderCourseArticle(String courseArticle) {
            this.courseArticle = courseArticle;
            return this;
        }
        public CourseBuilder builderCourseQA(String courseQA) {
            this.courseQA = courseQA;
            return this;
        }

        public Course build() {
            return new Course(this);
        }
    }

    @Override
    public String toString() {
        return "Course{" +
                "courseName='" + courseName + '\'' +
                ", coursePPT='" + coursePPT + '\'' +
                ", courseVideo='" + courseVideo + '\'' +
                ", courseArticle='" + courseArticle + '\'' +
                ", courseQA='" + courseQA + '\'' +
                '}';
    }
}

我们再来写上一个测试类来测试：

public class Test {
    public static void main(String[]args){
        Course course = new Course.CourseBuilder()
                .builderCourseName("Java设计模式")
                .builderCoursePPT("Java设计模式PPT")
                .builderCourseVideo("Java设计模式视频")
                .builderCourseArticle("Java设计模式手记")
                .builderCourseQA("Java设计模式问答").build();
        System.out.println(course);
    }
}

运行结果：

Course{courseName=‘Java设计模式’, coursePPT=‘Java设计模式PPT’, courseVideo=‘Java设计模式视频’, courseArticle=‘Java设计模式手记’, courseQA=‘Java设计模式问答’}

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这个就是现在的类图：

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7-3 建造者模式源码解析(jdk+guava+spring+mybatis)

StringBuilder

而StringBuffer里面同样也是如此，只不过方法里面加入了synchronized关键字

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Guava里面的 ：

测试：

    public static void main(String[]args){
        Set<String> set = ImmutableSet.<String>builder().add("a").add("b").build();
        System.out.println(set);
    }

运行结果：

[a, b]

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