java-list

某中学有若干学生学生对象放在一个List中，每个学生有一个姓名属性、班级名称属性(String)和考试成绩属性(int)，某次考试结束后，每个学生都获得了一个考试成绩。请打印出每个班级的总分和平均分。

源码如下：

package com.practice3;
/***
    * 自定义CompareTo接口
    * @author HDC
    */
public interface MyCompare<T> {
	int myCompareTo(T o);
}
package com.practice3;
/***
    * 自定义MySort排序
    */
import java.util.List;
public class MySort {
	public static <T extends MyCompare<T>> void sort(List<T> list) {
		for (int i = 0; i < list.size(); i++) {
			for (int j = 0; j < list.size(); j++) {
				if ((list.get(i)).myCompareTo(list.get(j))>0) {
					T t = list.get(i);
					list.set(i, list.get(j));
					list.set(j, t);
				}
			}
		}
	}
}

package com.practice3;
/***
    * 学生类里面有班级，姓名，成绩属性
    * @author HDC
    *
    */
public class Student implements MyCompare<Student>{
	private String name;
	private String cls;
	private int grade;
	public Student(String name,String cls,int grade){
		this.name=name;
		this.cls=cls;
		this.grade=grade;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getCls() {
		return cls;
	}
	public void setCls(String cls) {
		this.cls = cls;
	}
	public int getGrade() {
		return grade;
	}
	public void setGrade(int grade) {
		this.grade = grade;
	}
	@Override
	public int myCompareTo(Student o) {
		if(o.cls.compareTo(this.cls)!=0){
			return o.cls.compareTo(this.cls);
		}else if(o.name.compareTo(this.name)!=0){
			return o.name.compareTo(this.name);
		}else{
			return this.grade-o.grade;
		}
	}
}

package com.practice3;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

/***
    * 测试学生类  
    * @author HDC
    */
public class Test {
	public static void main(String[] args) {
		List<Student> std = new ArrayList<Student>();
		std.add(new Student("asd", "A", 80));
		std.add(new Student("qwe", "C", 70));
		std.add(new Student("zxc", "B", 60));
		std.add(new Student("aaa", "A", 70));
		std.add(new Student("sss", "C", 90));
		std.add(new Student("ddd", "C", 85));
		std.add(new Student("dfd", "B", 70));
		std.add(new Student("dfg", "A", 90));
		MySort.sort(std);
		for (Student s : std) {
			System.out.println(s.getCls()+"\t"+s.getName()+"\t"+s.getGrade());
		}
		System.out.println("---------------------------");
		//求平均分和总分
		Iterator<Student> it = std.iterator();// 使用迭代器
		Student s = it.next();// 获取对象
		String cls = s.getCls();
		int sum=s.getGrade(),i=1;
		while (it.hasNext()) {// 判断迭代器当中是否存在下一个数
			s = it.next();// 获取对象
			if(s.getCls()!=cls){
				System.out.println(cls+"班的总分为："+sum+"\t平均分是："+(double)sum/i);
				cls=s.getCls();
				i=1;
				sum=s.getGrade();
			}else{
				i++;
				sum+=s.getGrade();
			}
		}
		System.out.println(cls+"班的总分为："+sum+"\t平均分是："+(double)sum/i);
	}
}