Question

Design and code a JAVA program called ‘Grades’. ?

Your system should store student’s name, and his/her course names with grades. ?

Your system should allow the user to input, update, delete, list and search students’ grades. ?

Each student has a name (assuming no students share the same name) and some course/grade pairs. If an existing name detected, user can choose to quit or to add new courses to that student. ?

Each student has 1 to 5 courses, each course has a unique name and a grade from 0 to 100. ?

The course name has to be one of these 5 courses: Database, Data Structure, Operating System, Mathematics, and System Design.

Your system should provide below functions:

1. Add a student with course and grade pairs by: a. Spelling out the student’s name, and then provide “Course name” and “Grade” of that course to add a new student. b. Or add new course/grade pair to an existing student.

2. Delete a. A student by spelling out the student’s name. b. Or courses of a student by providing student’s name and course names.

3. Search a student’s grades by: a. Providing only the student’s name which will results to a list of course/grade pairs. Plus the average grade among all courses of that student. b. Or by providing student’s name and course(s) name(s) which will results to the grade of that course or grades of multiple courses.

4. Update student’s grades by: Providing student’s name, and then provide “Course name” of the required course and put the new “Grade”.

5. List all student/grade pairs of a course by: providing “Course name”. The list should be shown in descending orders of the grades, for same grades, list in ascending alphabetical order of students’ names. Also, the average grade should be shown.

Thank you so much for the work! really need your help!

Answer 1

CODE TO COPY:

import java.util.ArrayList;

import java.util.Arrays;

import java.util.Collections;

import java.util.Comparator;

import java.util.HashMap;

import java.util.Scanner;

public class Grades {

public static void main(String[] args) {

HashMap<String, HashMap<String, Double>> students=new HashMap<String, HashMap<String, Double>>();

Scanner obj=new Scanner(System.in);

int choice=-1;

char ch=' ';

String name=null, course=null;

double grade=0;

do {

switch(choice)

{

case 1:

System.out.println("Enter the student's name.");

name=obj.nextLine().toLowerCase();

System.out.println("Enter the course name.");

course=obj.nextLine().toLowerCase();

System.out.println("Enter the grade.");

grade=Double.parseDouble(obj.nextLine());

if(!students.containsKey(name))

{

students.put(name, new HashMap<String, Double>());

}

students.get(name).put(course, grade);

break;

case 2:

System.out.println("1. Delete student.");

System.out.println("2. Delete course of student.");

choice=Integer.parseInt(obj.nextLine());

System.out.println("Enter the student's name.");

name=obj.nextLine().toLowerCase();

if(choice==1)

{

students.remove(name);

}

else {

System.out.println("Enter the course name.");

course=obj.nextLine().toLowerCase();

students.get(name).remove(course);

}

break;

case 3:

System.out.println("1. Search for student's complete grades.");

System.out.println("2. Search for student's grades in multiple courses.");

choice=Integer.parseInt(obj.nextLine());

System.out.println("Enter the student's name.");

name=obj.nextLine().toLowerCase();

if(choice==1)

{

//print all grades

Object list[]=students.get(name).keySet().toArray();

System.out.printf("\n%30s%30s\n", "Course", "Grade");

double avg=0;

for(int i=0; i<list.length; i++)

{

System.out.printf("%30s%30f\n", (String)list[i], students.get(name).get((String)list[i]));

avg+=students.get(name).get((String)list[i]);

}

avg/=list.length;

System.out.println("Average Grade: "+avg);

}

else {

String list[]=new String[5];

int index=0;

do {

System.out.println("\nEnter a course name.");

course=obj.nextLine().toLowerCase();

list[index++]=course;

System.out.println("Do you want to enter another course? (Y/N)");

ch=obj.nextLine().charAt(0);

}while(ch=='Y' || ch=='y');

System.out.printf("\n%30s%30s\n", "Course", "Grade");

double avg=0;

for(int i=0; i<list.length; i++)

{

System.out.printf("%30s%30f\n", list[i], students.get(name).get(list[i]));

avg+=students.get(name).get(list[i]);

}

avg/=list.length;

System.out.println("Average Grade: "+avg);

}

break;

case 4:

System.out.println("Enter the student's name.");

name=obj.nextLine().toLowerCase();

System.out.println("Enter the course name.");

course=obj.nextLine().toLowerCase();

System.out.println("Enter the new grades.");

grade=Double.parseDouble(obj.nextLine());

students.get(name).put(course, grade);

break;

case 5:

{

System.out.println("Enter course name.");

String course_=obj.nextLine().toLowerCase();

ArrayList<String> names=new ArrayList<String>();

Object names_[]=students.keySet().toArray();

  

for(int i=0; i<names_.length; i++)

if(students.get((String)names_[i]).containsKey(course_))

names.add((String)names_[i]);

  

Comparator<String> cmp=new Comparator<String>()

{

public int compare(String a, String b)

{

if(students.get(a).get(course_)>students.get(b).get(course_))

return -1;

else if(students.get(a).get(course_)==students.get(b).get(course_))

return -1;

else

return 1;

}

};

  

Collections.sort(names, cmp);

double avg=0;

int stuCount=0;

System.out.printf("\n%30s%30s%30s\n", "Student Name", "Course Name", "Grades");

for(int i=0; i<names.size(); i++)

{

avg+=students.get(names.get(i)).get(course_);

System.out.printf("%30s%30s%30f\n", names.get(i), course_, students.get(names.get(i)).get(course_));

}

System.out.println("\nAverage Grade: "+(avg/names.size()));

}

break;

}

System.out.println("\n\n1. Insert");

System.out.println("2. Delete");

System.out.println("3. Search");

System.out.println("4. Update");

System.out.println("5. List all students grades by course name");

System.out.println("6. Exit");

choice=Integer.parseInt(obj.nextLine());

}while(choice!=6);

}

}

PROGRAM SCREENSHOTS:

OUTPUT:

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