- /*有五个学生,每个学生有3门课的成绩
- * 从键盘输入以上数据(包括姓名,三门课成绩),
- * 输入的格式:如:zhangsan,30,40,60计算出总成绩,
- * 并把学生的信息和计算出的总分数高低顺序存放在磁盘文件“stud.txt”中
- *
- * 1,描述学生对象
- * 2,定义一个可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,因为学生有很多,那么就需要存储,使用到集合。因为要对学生的总分排序,
- * 所以可以使用TreeSet
- * 3,将集合的信息写入到一个文件中
- */
- package day21;
- import java.io.*;
- import java.util.*;
- class Student implements Comparable<Student>
- {
- private String name;
- private int ma,cn,en;
- private int sum;
- Student(String name,int ma,int cn,int en)
- {
- this.name = name;
- this.ma = ma;
- this.cn = cn;
- this.en = en;
- sum = ma +cn+en;
- }
- public int compareTo(Student s)
- {
- int num = new Integer(this.sum).compareTo(new Integer(s.sum));
- if(num==0)
- return this.name.compareTo(s.name);
- return num;
- }
- public String getName()
- {
- return name;
- }
- public int getSum()
- {
- return sum;
- }
- public int hashCode()
- {
- return name.hashCode()+sum*78;
- }
- public boolean equals(Object obj)
- {
- if(!(obj instanceof Student))
- throw new ClassCastException("类型不匹配");
- Student s = (Student)obj;
- return this.name.equals(s.name)&&this.sum==s.sum;
- }
- public String toString()
- {
- return "Student["+name+","+ma+","+cn+","+en+"]";
- }
- }
- class StudentInfoTool
- {
- public static Set<Student> getStudents() throws IOException
- {
- return getStudents(null);
- }
- public static Set<Student> getStudents(Comparator<Student> cmp) throws IOException
- {
- BufferedReader bufr =
- new BufferedReader(new InputStreamReader(System.in));
- String line = null;
- Set<Student> stus = null;
- if(cmp==null)
- stus = new TreeSet<Student>();
- else
- stus = new TreeSet<Student>(cmp);
- while((line=bufr.readLine())!=null)
- {
- if("over".equals(line))
- break;
- String[] info = line.split(",");
- Student stu = new Student(info[0],Integer.parseInt(info[1]),
- Integer.parseInt(info[2]),Integer.parseInt(info[3]));
- stus.add(stu);
- }
- bufr.close();
- return stus;
- }
- public static void write2File(Set<Student> stus) throws IOException
- {
- BufferedWriter bufw = new BufferedWriter(new FileWriter("stuinfo.txt"));
- for(Student stu : stus)
- {
- bufw.write(stu.toString()+"\t");
- bufw.write(stu.getSum()+"");
- bufw.newLine();
- bufw.flush();
- }
- bufw.close();
- }
- }
- class StudentInfoTest
- {
- public static void main(String[] args) throws IOException
- {
- Comparator<Student> cmp = Collections.reverseOrder();
- Set<Student> stus = StudentInfoTool.getStudents(cmp);
- StudentInfoTool.write2File(stus);
- }
- }
复制代码 对这个例子不是很理解,获取学生信息时定义了2个方法,一个用指定比较器,一个用默认方法比较,具体使用哪个,怎么调用的,求哪个大神讲解下,谢谢
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