sortMathByAverage() 的测试出现问题

相关代码（School类）：

package com.comp.stumanage;

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

public class School {
	// 属性：存放班级的集合
	private Map<String, BanJi> schoolMap;

	// 无参构造
	public School() {
		// 注意：实例化 schoolMap
		schoolMap = new HashMap<String, BanJi>();
	}

	// getters and setters
	public Map<String, BanJi> getSchoolMap() {
		return schoolMap;
	}

	public void setSchoolMap(Map<String, BanJi> schoolMap) {
		this.schoolMap = schoolMap;
	}

	/**
	 * 显示所有班级名称
	 */
	public void displayBanJiName() {
		// 注意：Map能生成的 set只有 .keySet() 和 .entrySet()，没有 .valueSet()
		Set<String> nameset = schoolMap.keySet();
		for (String s : nameset) {
			System.out.println(s);
		}
	}

	/**
	 * 添加班级
	 * 
	 * @param bj 班级信息
	 */
	public void addBanji(BanJi bj) {
		Set<String> keyset = schoolMap.keySet();
		String bjName = bj.getClassName();
		for (String s : keyset) {
			if (s.equals(bjName)) {
				System.out.println("班级已存在，请重新输入...");
				return;
			}
		}
		schoolMap.put(bjName, bj);
		System.out.println("添加成功");
	}

	/**
	 * 根据班级名字找到班级
	 * 
	 * @param className 要找到的班级的名字
	 * @return 班级
	 */
	public BanJi searchByName(String className) {
		Set<String> keyset = schoolMap.keySet();
		// 注意：因为在没有找到对应班级名时应该返回 null，所以就直接设定返回变量为 null就好了
		BanJi bj = null;
		for (String s : keyset) {
			if (s.equals(className)) {
				bj = schoolMap.get(s);
				break;
			}
		}
		return bj;
	}

	/**
	 * 删除班级
	 * 
	 * @param bj 要删除的班级
	 */
	public void deleteBanji(BanJi bj) {
		Set<String> keyset = schoolMap.keySet();
		for (String s : keyset) {
			if (schoolMap.get(s).equals(bj)) {
				schoolMap.remove(s);
				return;
			}
		}

	}

	/**
	 * 对各班的语文平均成绩进行排序
	 */
	public void sortChineseByAverage() {
		Iterator<Entry<String, BanJi>> it = schoolMap.entrySet().iterator();
		Map<Double, String> averageScoreMap = new HashMap<Double, String>();
		List<Double> sortList = new ArrayList<Double>();
		// 做 map，key 为平均成绩，value 为班级名，然后对平均成绩进行排序，之后就可以通过 getValue 获得班级名
		while (it.hasNext()) {
			BanJi bj = it.next().getValue();
			List<Student> stuList = bj.getStuList();
			double sum = 0;
			for (Student stu : stuList) {
				sum += stu.getChinese();
			}
			sum = sum / bj.getStuList().size();
			averageScoreMap.put(sum, bj.getClassName());
			sortList.add(sum);
		}
		Collections.sort(sortList, new ScoreComparator());
		for (Double d : sortList) {
			String s = averageScoreMap.get(d);
			System.out.println("班级：" + s + "，中文平均成绩为：" + d);
		}

	}

	/**
	* 对各班的数学平均成绩进行排序
	*/
	public void sortMathByAverage() {
		Iterator<Entry<String, BanJi>> it = schoolMap.entrySet().iterator();
		Map<Double, String> averageScoreMap = new HashMap<Double, String>();
		List<Double> sortList = new ArrayList<Double>();
		// 做 map，key 为平均成绩，value 为班级名，然后对平均成绩进行排序，之后就可以通过 getValue 获得班级名
		while (it.hasNext()) {
			BanJi bj = it.next().getValue();
			List<Student> stuList = bj.getStuList();
			double sum = 0;
			for (Student stu : stuList) {
				sum += stu.getMath();
			}
			sum = sum / bj.getStuList().size();
			averageScoreMap.put(sum, bj.getClassName());
			sortList.add(sum);
		}
		Collections.sort(sortList,new ScoreComparator());
		for (Double d : sortList) {
			String s = averageScoreMap.get(d);
			System.out.println("班级：" + s + "，数学平均成绩为：" + d);
		}

	}
}

相关代码（Comparator 实现）：

package com.comp.stumanage;

import java.util.Comparator;

public class ScoreComparator implements Comparator<Double> {

	@Override
	public int compare(Double arg0, Double arg1) {
		// TODO Auto-generated method stub
		int n=new Double(arg1-arg0).intValue();
		return n;
	}


}

相关代码（Test类）：

package com.comp.test;

import com.comp.stumanage.BanJi;
import com.comp.stumanage.School;
import com.comp.stumanage.Student;

public class StuManageTest {

	public void stuTest() {
            ...
	}

	public void testBanJi() {
	    ...
	}

	public void testSchool() {
		//测试构造函数
		School school=new School();
		BanJi bj=new BanJi("b001","一班");
		BanJi bj0=new BanJi("b001","一班");

		//测试 addBanji
		school.addBanji(bj);
		school.addBanji(bj0);

		//测试 displayBanJiName
		System.out.println("***");
		school.displayBanJiName();

		//测试 searchByName
		System.out.println("***");
		if((bj=school.searchByName("零班"))==null)
			System.out.println("该班级不存在");
		else
			System.out.println(bj.getClassName());

		if((bj=school.searchByName("一班"))==null)
			System.out.println("该班级不存在");
		else
			System.out.println(bj.getClassName());

		//测试 deleteBanji
		System.out.println("***");
		BanJi bj2=new BanJi("b002","二班");
		school.addBanji(bj2);
		school.deleteBanji(bj);
		school.displayBanJiName();

		//测试 sortChineseByAverage
		System.out.println("***");
		BanJi bj3=new BanJi("b003","三班");
		school.addBanji(bj);
		school.addBanji(bj3);
		Student stu1=new Student("s001","张三",3,86);
		Student stu2=new Student("s002","李四",2,93);
		Student stu3=new Student("s003","王五",3,90);
		Student stu11=new Student("s0011","张三",50,87);
		Student stu22=new Student("s0022","李四",50,94);
		Student stu33=new Student("s0033","王五",50,91);
		bj.addStudent(stu1);
		bj2.addStudent(stu2);
		bj3.addStudent(stu3);
		bj.addStudent(stu11);
		bj2.addStudent(stu22);
		bj3.addStudent(stu33);
		school.sortChineseByAverage();

		//测试 sortMathByAverage
		System.out.println("***");
		school.sortMathByAverage();
	}

	public static void main(String[] args) {
		StuManageTest test=new StuManageTest();
		test.testSchool();
	}
}

相关截图：

问题描述：

为什么在 sortMathByAverage() 中平均成绩排序没有从大到小排呢？

sortMathByAverage() 的代码和 sortChineseByAverage() 是一样的。

是 Comparator() 哪里写错了吗？