关于私有成员变量的成员调用问题 - 黑马程序员技术交流社区

import java.util.*;
import java.io.*;
class Student implements Comparable<Student>
{
private String name;
private int en,cn,ma;
private int sum;
Student(String name,int en,int cn,int ma)
{
this.name=name;
this.en=en;
this.cn=cn;
this.ma=ma;
sum=en+cn+ma;
}
public String getSum()
{
return this.name;
}
public int compareTo(Student stu)
{
if(this.sum==stu.sum)//为什么可以stu.sum而不报错？sum不是私有变量吗？why?
return this.name.compareTo(stu.name);
return this.sum-stu.sum;
}
public int hashCode()
{
return name.hashCode()+sum*36;
}
public boolean equals(Object obj)
{
if(obj instanceof Student)
return false;
Student s=(Student)obj;
return s.name.equals(this.name) && s.sum==this.sum;
}
public String toString()
{
return "student"+"["+name+","+ma+","+en+","+cn+","+sum+"]";
}
}
class StudentTool
{
public static Set<Student> getStudents() throws IOException
{
Set<Student> set=new TreeSet<Student>();
BufferedReader bufr=
new BufferedReader(new InputStreamReader(System.in));
String line=null;
while((line=bufr.readLine())!=null)
{
if("over".equals(line))
break;
String[] info=line.split(",");
Student s=new Student(info[0],Integer.parseInt(info[1]),Integer.parseInt(info[2]),Integer.parseInt(info[3]));
set.add(s);
}
bufr.close();
return set;
}
public static void write2File(Set<Student> stu) throws IOException
{
BufferedWriter bw=new BufferedWriter(new FileWriter("student.txt"));
for(Student s : stu)
{
bw.write(s.toString()+"\t");
bw.write(s.getSum());
bw.newLine();
bw.flush();
}
bw.close();
}
}
class StudentsIOTest
{
public static void main(String[] args) throws IOException
{
Set<Student> ts=StudentTool.getStudents();
StudentTool.write2File(ts);
}
}

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