7-1 建造者模式讲解
7-2 建造者模式coding
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:
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’}
我们可以打个断点来看看执行过程:
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’}
这个就是现在的类图:
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
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]