首先是数据的基本类Student:
public class Student{
private String name;
private int score;
public Student(String name,int score){
this.name=name;
this.score=score;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getScore() {
return score;
}
public void setScore(int score) {
this.score = score;
}
}
然后是用于分类汇总的类,它强制子类实现getKey和getvalue两个方法:
public abstract class ClassifyRule {
public Student student;
public ClassifyRule(){
}
public void setStudent(Student student) {
this.student = student;
}
abstract public String getKey();
abstract public int getValue();
}
接下来是对Student进行CRUD处理的StudentService类,注意getSum方法,它保留了筛选过程,筛选规则则不在其中:
import java.util.ArrayList;
import java.util.Hashtable;
import java.util.List;
public class StudentService {
private List
public StudentService() {
students = new ArrayList
}
public void add(Student student) {
students.add(student);
}
public Hashtable getSum(ClassifyRule rule) {
Hashtable ht = new Hashtable();
for (Student student : students) {
rule.setStudent(student);
String key = rule.getKey();
int value = rule.getValue();
if (ht.containsKey(key)) {
Integer oldValue = ht.remove(key);
oldValue += value;
ht.put(key, oldValue);
} else {
ht.put(key, value);
}
}
return ht;
}
}
最后是测试代码,注意其中筛选规则的创建:
import java.util.Hashtable;
import java.util.Iterator;
public class Test {
public static void main(String[] args) {
// 初始化
StudentService service = new StudentService();
service.add(new Student("Andy", 90));
service.add(new Student("Bill", 95));
service.add(new Student("Cindy", 70));
service.add(new Student("Dural", 85));
service.add(new Student("Edin", 60));
service.add(new Student("Felix", 55));
service.add(new Student("Green", 15));
// 60分及格筛选
ClassifyRule rule60 = new ClassifyRule() {
public String getKey() {
return student.getScore() >= 60 ? "及格" : "不及格";
}
public int getValue() {
return 1;
}
};
System.out.println("60分及格筛选");
printHt(service.getSum(rule60));
// 50分及格筛选
ClassifyRule rule50 = new ClassifyRule() {
public String getKey() {
return student.getScore() >= 50 ? "及格" : "不及格";
}
public int getValue() {
return 1;
}
};
System.out.println("\n50分及格筛选");
printHt(service.getSum(rule50));
// 分"优良中差"等级
ClassifyRule ruleCn = new ClassifyRule() {
public String getKey() {
String retval = "";
int score = student.getScore();
if (score >= 90) {
retval = "优";
} else if (score >= 80) {
retval = "良";
} else if (score >= 60) {
retval = "中";
} else if (score > 0) {
retval = "差";
}
return retval;
