import java.io.*;

class student
{
    private String name;
    private String id;  // hofstra id number
    private char grade;
    public String name() { return name; }
    public char grade() { return grade; }
    public student(String n, String i, char g) 
    { name=n; id = i; 
      grade = g;
    }
    public void setgrade(char newgrade) { grade=newgrade; }
    public double gradepoint()
    {
	if (grade=='F') return 0;
	  else return 4.0-((int)grade-65);
    }

    public void writeXML(PrintWriter pw ) throws Exception
    {
	pw.println("<student name=\""+name+"\">");
	pw.println("   <id>"+id+"</id>");
	pw.print("   <grade>");
	if (grade=='N') pw.print("no grade"); else
	    pw.print(grade);
	pw.println("</grade>");
	pw.println("</student>");
    }
}  // student


class csc15 // ha ha
{
    private student[] roster;
    private int size;  // the size is not necessarily the size of the class.

    public csc15()
    {
	roster = new student[25];  // 25 is max enrollment
        size = 0;
    }

    // add a student
    public void addstudent(String name, String id, char g) throws Exception
    {
	if (size>= roster.length) throw new Exception("class full");
	student stu = new student(name,id,g);
	roster[size] = stu;
	size++;
    }
    
    // lookup the grade for a student:
    public char gradefor(String name) throws Exception
    {
	char answer = 'E';  // 'E' indicates no grade.
	int i = 0;
        while(i<size && answer == 'E')
	    {
		if (roster[i].name() == name) answer = roster[i].grade();
		i++;
	    }
	if (answer == 'E') throw new Exception("no such student");
	return answer;			
    }

    // print all students who have a certain grade in the class
    public void havegrade(char g)
    {
	int i;
	for(i=0;i<size;i++)
	    { if (roster[i].grade()==g) 
		System.out.println(roster[i].name());
	    }
    }

    // write database to a printwriter in xml format
    public void writeXML(PrintWriter pw) throws Exception
    {   int i;
	pw.println("<?xml version=\"1.0\" ?>");
	pw.println("<roster>\n");
	for(i=0;i<size;i++)
	    { roster[i].writeXML(pw); }
	pw.println("\n</roster>");
    }
} // csc15 class

public class nov19
{
    public static void main(String[] args)
    {
	csc15 section1 = new csc15();
	csc15 section2 = new csc15();
        try {

	section1.addstudent("bilbo","700000000",'A');
	section1.addstudent("frodo","700000001",'B');
	section1.addstudent("gandolf","700000002",'A');
	System.out.println("frodo have grade "+section1.gradefor("frodo"));
	section1.havegrade('A');

	FileOutputStream fos = new FileOutputStream("section1.roster");
	PrintWriter pw = new PrintWriter(new OutputStreamWriter(fos));
	section1.writeXML(pw);
	pw.close();

	} catch (Exception e) {System.out.println(e);}

    } // main
}