1、建造者定义
将一个复杂对象的构建与它的表示分离,使得同样的构建过程可以创建不同的表示。用户只需要指定需要创建的类型就可以得到它们,建造过程及细节不需要知道。适用场景:1) 如果一个对象具有非常复杂的内部结构(很多属性)2) 想把复杂对象的创建和使用分离优点:1) 封装性好,创建和使用分离2) 扩展性好、建造类之间独立,一定程度上解耦缺点:1) 产生多余的Builder对象2) 产品内部发生变化,建造者都要修改,成本较大
2、代码演示
public class Course { private String courseName; private String coursePPT; private String courseVideo; private String courseArticle; 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; private String courseQA; public CourseBuilder buildCourseName(String courseName){ this.courseName = courseName; return this; } public CourseBuilder buildCoursePPT(String coursePPT) { this.coursePPT = coursePPT; return this; }
public CourseBuilder buildCourseVideo(String courseVideo) { this.courseVideo = courseVideo; return this; } public CourseBuilder buildCourseArticle(String courseArticle) { this.courseArticle = courseArticle; return this; } public CourseBuilder buildCourseQA(String courseQA) { this.courseQA = courseQA; return this; } public Course build(){ return new Course(this); } }}
public class Test { public static void main(String[] args) { Course course = new Course.CourseBuilder() .buildCourseName("Java设计模式精讲") .buildCoursePPT("Java设计模式精讲PPT") .buildCourseVideo("Java设计模式精讲视频").build(); System.out.println(course); Set<String> set = ImmutableSet.<String>builder().add("a").add("b").build(); System.out.println(set); }}