请高手能够解释下这段程序每行的大致意思

请高手能够解释下这段程序每行的大致意思
public class Test {
public static void main(String[] args)
{
Student st=new Student("张","男",123456);
st.setEnglish(91);
st.setMath(96);
st.setComputer(98);
st.Total();
st.Average();
System.out.println("张的总成绩是："+st.getTotal());
System.out.println("张的平均成绩是："+st.getAverage());
Graduate gra=new Graduate("王五","男",20090201);
gra.setComputer(85);
gra.setMath(73);
gra.setEnglish(96);
gra.Total();
gra.Average();
System.out.println("王五的总成绩是："+gra.getTotal());
System.out.println("王五的平均成绩是："+gra.getAverage());
}
}
class Graduate extends Student{
public Graduate(String na,String s,long n) {
super(na,s,n);
}
private String major;
private String researchDirection;
private double analyzeScore;
private int analyseScore;
public void Total()
{
super.total= analyseScore+super.com_score+super.math_score;
}
public void Average()
{
super.ave=(analyseScore+super.com_score+super.math_score)/3;
}
}
class Student {
private String name;
private String sex;
private long number;
private int en_score;
protected int math_score;
protected int com_score;
protected double ave;
protected double total;
public Student(String na,String s,long n)
{
this.name=na;
this.sex=s;
this.number=n;
}
public void Total()
{
this.total=en_score+math_score+com_score;
}
public void Average()
{
this.ave=(en_score+math_score+com_score)/3;
}
public void setName(String na)
{
this.name=na;
}
public void setNumber(long nb)
{
this.number=nb;
}
public void setSex(String s)
{
this.sex=s;
}
public void setEnglish(int a)
{
this.en_score=a;
}
public void setMath(int b)
{
this.math_score=b;
}
public void setComputer(int c)
{
this.com_score=c;
}
public String getName()
{
return name;
}
public long getNumber()
{
return number;
}
public String getSex()
{
return sex;
}
public int getEnglish()
{
return en_score;
}
public int getMath()
{
return math_score;
}
public int getComputer()
{
return com_score;
}
public double getTotal()
{
return total;
}
public double getAverage()
{
return ave;
}
}