有5个学生,每个学生有三门课程,从键盘输入以上数据(包括姓名、三门课成绩)输入格式:如zhangsan,30,40,50计算出总成绩,并将学生的信息和计算出的总分数从高到底存放在磁盘文件“stu.txt”
1,描述学生对象
2,定义一个可以操作学生对象的工具类
思想:
1,通过获取键盘录入一行数据,并将该行中的信息取出封装成学生对象
2,因为你学生有很多,那么就需要存储,使用集合,因为要对学生的总分数进行排序,所以可以用用TreeSet
3,将集合的信息写入到文件
//学生类
public class Student implements Comparable<Student> {
private String name;
private int chinGrade;
private int mathGrade;
private int engGrade;
private int sumGrade;
Student(String name,int chinGrade,int mathGrade,int engGrade ){
this.name=name;
this.chinGrade=chinGrade;
this.mathGrade=mathGrade;
this.engGrade=engGrade;
sumGrade= chinGrade+mathGrade+ engGrade;
}
//可能被二叉树使用
public int compareTo(Student stu) {
if(this.sumGrade>stu.sumGrade)
return -1;
if(this.sumGrade==stu.sumGrade)
return this.name.compareTo(stu.name);
return 1;
}
public int getSumGrade() {
return sumGrade;
}
public String getName() {
return name;
}
//可能被哈希用到
public int hashCode() {
return name.hashCode()+sumGrade*85;
}
public boolean equals(Object obj) {
if(!(obj instanceof Student ))
throw new ClassCastException();
Student stu=(Student)obj;
return this.getName().equals(stu.getName())&&this.sumGrade==stu.sumGrade;
}
public String toString() {
return "姓名:"+name+" 语文:"+chinGrade+" 数学:"+mathGrade+" 英语"+engGrade+" 总分:"+sumGrade;
}
}
//
import java.io.*;
import java.util.*;
public class StuDemo {
public static TreeSet<Student> getStudents() throws IOException{
return getStudents(null);
}
public static TreeSet<Student> getStudents(Comparator<Student> cmp) throws IOException//将数据写入集合
{
TreeSet<Student> ts=null;
if(cmp==null)
ts=new TreeSet<Student>();
else
ts=new TreeSet<Student>(cmp);
int count=1;
while(count<=5)
{
System.out.println("请输入第"+count+"名学生的信息");
BufferedReader bufr=new BufferedReader(new InputStreamReader(System.in));
String line=bufr.readLine();
String[] every=line.split(",");
//将键盘输入的数据封装成对象
ts.add(new Student(every[0],Integer.parseInt(every[1]),Integer.parseInt(every[2]),Integer.parseInt(every[3])));
count++;
}
return ts;
}
public static void write2File(TreeSet<Student> ts)throws IOException//将集合中的数据写入文件
{
//将集合中的数据写入文件中
FileWriter fos=new FileWriter("E:\\grade.txt");//因为要用到一行一行的写,所以用Writer
BufferedWriter bufw=new BufferedWriter(fos);
bufw.write("学生成绩以及排名如下:");
bufw.newLine();
Iterator<Student> it=ts.iterator();
while(it.hasNext()) {
Student stu=it.next();
bufw.write(stu.toString());
bufw.newLine();
bufw.flush();
}
bufw.close();
}
public static void main(String[] args)throws IOException {
//Comparator<Student> cmp=Collections.reverseOrder(new MyComp());
//TreeSet ts=getStudents(cmp);//用比较器比较
TreeSet ts=getStudents();//用compareTo比较
write2File(ts);
}
}
//升序比较器
public class MyComp implements Comparator<Student>{
public int compare(Student stu1,Student stu2){
if(stu1.getSumGrade()>stu2.getSumGrade())
return 1;
if(stu1.getSumGrade()>stu2.getSumGrade())
return stu1.getName().compareTo(stu2.getName());
return -1;
}
}