sorted merge nd student problem

[garima]

hey guys n gals,
i m having problem in implementing sorted merge op on arrays.another
problem is finding highest marks in each grade in a group of
students.anyone with the solution plz.

[manish]

class TwoDArrayTest
{
public static void main(String s[])
{
int a[][];
int nor=6;
int noc=5;
int sum=0;
int avg=0;
a=new int[nor][noc];
for(int i=0;i<a.length;i++)
{
for(int j=0;j<a[i].length;j++)
{
a[i][j]=(int)(Math.random()*100);
sum+=a[i][j];
avg =sum/noc;
System.out.print("\t"+a[i][j]);
}
System.out.print("\t"+sum);
System.out.print("\t"+avg);
System.out.println();
sum=0;
avg=0;
}
}
}

[manish]

class Student
{
static int i,j,k,l,m;
int roll,marks;
String name;
char Grade;
Student(int roll,String name)
{
this.roll=roll;
this.name=name;
}
Student()
{}
void exam(int marks)
{
this.marks=marks;
}
void show()
{
Grade=grade();

System.out.println(name +"\t"+roll +"\t"+marks+"\t"+Grade+"\t");
}
char grade()
{
if(marks>=85)
{
i++;
return 'A';

}
else if(marks>=75)
{
j++;
return 'B';
}
else if(marks>=60)
{
k++;
return 'C';
}
else if(marks>=45)
{
l++;
return 'D';
}
else
{
m++;
return 'E';
}
}
}

class StudentOperation
{
void sort(Student st[])
{
Student temp;
for(int i=0;i<st.length;i++)
{
for(int j=i+1;j<st.length;j++)
{
if(st[i].marks<st[j].marks)
{
temp=st[i];
st[i]=st[j];
st[j]=temp;
/*st[i]=st[i]+st[j];
st[j]=st[i]-st[j];
st[i]=st[j]-st[i];*/
}
}
}
}


}
class RefArrayTest

{
public static void main(String s[])
{

Student st[]=new Student[10];
for(int i=0;i<st.length;i++)
{
st[i]=new Student(101+i,s[i]);
int m=(int)(Math.random()*101);
st[i].exam(m);
}
System.out.println("list of student");
System.out.println("\nName\tRoll\tMarks\tGrade");
System.out.println();
for(int i=0;i<st.length;i++)
{
st[i].show();
}
Student s1=new Student();
System.out.println("Number of student in grade A "+s1.i );
System.out.println("Number of student in grade B "+s1.j );
System.out.println("Number of student in grade C "+s1.k );
System.out.println("Number of student in grade D "+s1.l );
System.out.println("Number of student in grade E "+s1.m );
StudentOperation op=new StudentOperation();
op.sort(st);
System.out.println("\nsorted list");
for(int i=0;i<st.length;i++)
{
st[i].show();
}


}
}

[garima yadav]

thanks but isme meri problem ka solution nhi h.i am having problem in
implementing 'find highest marks in each grade'.