Sunny 公司欲为某高校开发一套奖励审批系统，该系统可以实现教师奖励和学生审批（Award Check）。如果教师发表的论文数超过 10 篇或学生发表论文数超过 2 篇可以评选科研奖，如果教师教学反馈分大于等于 90 分或学生平均成绩大于等于 90 分可以评选成绩优秀奖。试使用访问者模式设计该系统，以判断候选人集合中的教师或学生是否符合某种获奖要求。
一、类结构图
抽象访问者类：设计为名称为 AwardChecker 的抽象类，面向具体元素类编程，包含访问具体候选人类 Teacher 的抽象方法 visit(Teacher teacher)、访问具体候选人类 Student 的抽象方法 visit(Student student)；
抽象元素类：设计为名称为 Candidate 的接口，面向抽象访问者类编程，包含接受访问的抽象方法 accept(AwardChecker awardChecker)；
具体访问者类：设计为抽象访问者类的子类，包括科研奖具体访问者类 ResearchAwardChecker、优秀成绩奖具体访问者类 ScoreAwardChecker，访问者类内部分别实现抽象方法 visit(Teacher teacher)、抽象方法 visit(Student student)；
具体元素类：设计为抽象元素类 Candidate 的子类，包括具体元素类 Teacher、具体元素类 Student，分类实现抽象方法 accept(AwardChecker awardChecker)；
对象结构类：设计为名称为 CandidateList 的具体类，面向抽象访问者类和抽象元素类编程，持有一个抽象元素 list 的引用，包含添加抽象元素类的具体方法 add(Candidate candidate)、接受抽象访问者类访问的具体方法 accept(AwardChecker awardChecker)。
二、典型实现代码
抽象奖项评选类：抽象访问者类
// 抽象奖项评选类：抽象访问者类public abstract class AwardChecker { public abstract void visit(Teacher teacher); public abstract void visit(Student student);}
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抽象候选者类：抽象元素类
// 抽象候选者类：抽象元素类public interface Candidate { void accept(AwardChecker awardChecker);}
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科研奖项评选类：具体访问者类
// 科研奖项评选类：具体访问者类public class ResearchAwardChecker extends AwardChecker{ private String awardName = "科研奖";
@Override public void visit(Teacher teacher) { if (teacher.getPaperAmount() > 10) { System.out.println(teacher.getName() + "获得" + this.awardName); } }
@Override public void visit(Student student) { if (student.getPaperAmount() > 2) { System.out.println(student.getName() + "获得" + this.awardName); } }}
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成绩优秀奖项评选类：具体访问者类
// 成绩优秀奖项评选类：具体访问者类public class ScoreAwardChecker extends AwardChecker{ private String awardName = "成绩优秀奖";
@Override public void visit(Teacher teacher) { if (teacher.getTeacherScore() >= 90) { System.out.println(teacher.getName() + "获得" + this.awardName); } }
@Override public void visit(Student student) { if (student.getScore() >= 90) { System.out.println(student.getName() + "获得" + this.awardName); } }}
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教师候选者类：具体元素类
// 教师候选者类：具体元素类public class Teacher implements Candidate{ private String name; private Integer paperAmount; private Integer teacherScore;
public Teacher(String name, Integer paperAmount, Integer teacherScore) { this.name = name; this.paperAmount = paperAmount; this.teacherScore = teacherScore; }
public String getName() { return name; }
public void setName(String name) { this.name = name; }
public Integer getPaperAmount() { return paperAmount; }
public void setPaperAmount(Integer paperAmount) { this.paperAmount = paperAmount; }
public Integer getTeacherScore() { return teacherScore; }
public void setTeacherScore(Integer teacherScore) { this.teacherScore = teacherScore; } @Override public void accept(AwardChecker awardChecker) { awardChecker.visit(this); }}
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学生候选者类：具体元素类
// 学生候选者类：具体元素类public class Student implements Candidate{ private String name; private Integer paperAmount; private Integer score;
public Student(String name, Integer paperAmount, Integer score) { this.name = name; this.paperAmount = paperAmount; this.score = score; }
public String getName() { return name; }
public void setName(String name) { this.name = name; }
public Integer getPaperAmount() { return paperAmount; }
public void setPaperAmount(Integer paperAmount) { this.paperAmount = paperAmount; }
public Integer getScore() { return score; }
public void setScore(Integer score) { this.score = score; }
@Override public void accept(AwardChecker awardChecker) { awardChecker.visit(this); }}
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候选者容器类：对象结构类
// 候选者容器类：对象结构类public class CandidateList { private ArrayList<Candidate> list = new ArrayList<Candidate>();
public void addCandidate(Candidate candidate) { this.list.add(candidate); }
public void accept(AwardChecker awardChecker) { for (Candidate candidate : list) { candidate.accept(awardChecker); } }}
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客户端代码：
public class Client { public static void main(String[] args) { CandidateList candidateList = new CandidateList(); Candidate teacher, student; teacher = new Teacher("张无忌", 10, 90); student = new Student("杨过", 5, 91); candidateList.addCandidate(teacher); candidateList.addCandidate(student);
AwardChecker researchAwardChecker, scoreAwardChecker; researchAwardChecker = new ResearchAwardChecker(); scoreAwardChecker = new ScoreAwardChecker(); candidateList.accept(researchAwardChecker); candidateList.accept(scoreAwardChecker); }}
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编译并运行程序，输出如下结果：
杨过获得科研奖张无忌获得成绩优秀奖杨过获得成绩优秀奖
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