Question

Please help. I need a very simple code. For a CS 1 class.

Write a program in Java and run it in BlueJ according to the following specifications:

• The program reads a text file with student records (first name, last name and grade).
• Then it prompts the user to enter a command, executes the command and loops. The commands are the following:
  • "printall" - prints all student records (first name, last name, grade).
  • "firstname name" - prints all students with first name that starts with the provided parameter name.
  • "lastname name" - prints all students with first name that starts with the provided parameter name.
  • "interval m n" - prints all students with grades in the interval [m, n].
  • "end" - exits the loop the terminates the program.
• For example, if the input text file is students.txt and the user enters "printall" the program prints the following:

John Smith 90 

Barack Obama 95 

Al Clark 80 

Sue Taylor 55 

Ann Miller 75 

George Bush 58 

John Miller 65 

If the user enters "firstname A" the program prints the following:  

Al Clark 80 

Ann Miller 75 

If the user enters "lastname Miller" the program prints the following:

Ann Miller 75 

John Miller 65  

If the user enters "interval 75 90" the program prints the following:

John Smith 90 

Al Clark 80 

Ann Miller 75 

Requirements and restrictions:

1. Use the Student.java and Students.java classes from the course website to represent and process student records and modify them accordingly:
   • Define and use an array of objects of class Student to store all student records read from the file.
   • In class Students define the following methods that accept the array of students and other proper parameters and do the following:
   • • Prints all student records in the array.
     • Prints all students with first name that starts with the provided parameter. Hint: use the indexOf(String str) method form class String.
     • Prints all students with last that starts with the provided parameter. Hint: use the indexOf(String str) method form class String.
     • prints all students with grades in the interval [m, n].
   • Do NOT use the array of Students directly in the main method, all processing must be done by the methods described above using the array passed to them as a parameter.
   • Enforce the encapsulation principle.
   • No need to verify the user input.
2. When you write your program
   • use proper names for the variables suggesting their purpose.
   • format your code accordingly using indentation and spacing.
   • use multiple line comment in the beginning of the code and write your name, e-mail address, class, and section.
   • for each line of code add a short comment to explain its meaning.

Extra credit (up to 2 points):

The extra credit will be given for extending the program to accept the "sort" command that will print the array of students sorted by grade. Use the bubble sort algorithm as implemented in array.java.

students:

(John Smith 90

Barack Obama 95

Al Clark 80

Sue Taylor 55

Ann Miller 75

George Bush 58

John Miller 65)

Array: (

// A program demonstrating the use of arrays
// arrays parameters, min, max and bubble sort

import java.util.Scanner;

class array {

public static void main (String[] args)
{

Scanner scan = new Scanner(System.in);

int [] a = new int [100];
int i, n = 0, min, max;
float total = 0;

System.out.println ("Enter integers separated by blanks (non-integer to end):");

while (scan.hasNextInt()) {
a[n] = scan.nextInt();
n = n + 1;
}

System.out.println ("You entered " + n + " numbers");
  
swap(a,0,n-1);
  
System.out.println ("After swapping elements 0 and " + (n-1));
for (i=0; i<n; i++)
System.out.print (a[i] + " ");
System.out.println ();

min = a[0];
max = a[0];
for (i = 1; i < n; i++) {
if (max < a[i]) max = a[i];
if (min > a[i]) min = a[i];
total = total + a[i];
}

System.out.print ("Min = " + min + ", Max = " + max + ", Average = " + total/n);

int t, swaps = 0;
do {
swaps = 0;
for (i=0; i<n-1; i++)
if (a[i]>a[i+1]) {
t=a[i];
a[i]=a[i+1];
a[i+1]=t;
swaps++;
}
} while (swaps>0);

System.out.print ("\nSorted: ");
for (i=0; i<n; i++)
System.out.print (a[i] + " ");
System.out.println ();

}

public static void swap(int arr[], int i, int j)
{
int temp=arr[i];
arr[i]=arr[j];
arr[j]=temp;
}
}
)

Answer 1

As per the problem statement I have solve the problem. Please let me know if you have any doubts or you want me to modify the answer. And if you find this answer useful then don't forget to rate my answer as thumps up. Thank you! :)

import java.util.Scanner;
import java.io.*;

public class StudentDatabaseDriver
{
    public static void main (String[] args) throws IOException {
        String studentName, grades;
        int studentgrade, totalStudents=0, totalexcellentStudents=0, totalOkStudents=0, totalFailStudents=0, countStudents=0, countExcellentStudents=0, countOkStudents=0, countFailStudents=0;

        double averageGrades, averageGradesOfExcellentStudents, averageGradesOfOkStudents, averageGradesOfFailStudents;
        Scanner studetnsDataInput = new Scanner(new File("/Users/swapnil/IdeaProjects/StudentDatabase/src/students.txt"));
        while (studetnsDataInput.hasNext())
        {
            //set student name format first nam and last name
            studentName = studetnsDataInput.next() + " " + studetnsDataInput.next();

            //grades of current student
            studentgrade = studetnsDataInput.nextInt();

            //students grades
            grades = studentGradeName(studentgrade);

            //new student object for current student
            Student student = new Student(studentName, studentgrade, grades);
            //counts and totals Excellent students
            if (grades == "Excellent")
            {
                totalexcellentStudents = totalexcellentStudents + studentgrade;
                countExcellentStudents++;
            }
            //counts and totals OK students
            if (grades == "OK")
            {
                totalOkStudents = totalOkStudents + studentgrade;
                countOkStudents++;
            }
            //counts and totals Fail students
            if (grades == "Fail")
            {
                totalFailStudents = totalFailStudents + studentgrade;
                countFailStudents++;
            }

            //prints out students information
            System.out.println(student);

            totalStudents = totalStudents + studentgrade;
            countStudents++;
        }
        //all type of average grades calculations
        averageGrades = (double)totalStudents/countStudents;
        averageGradesOfExcellentStudents = (double)totalexcellentStudents/countExcellentStudents;
        averageGradesOfOkStudents = (double)totalOkStudents/countOkStudents;
        averageGradesOfFailStudents = (double)totalFailStudents/countFailStudents;
        //Prints for user
        System.out.println("There are total " + countStudents + " students with average grade " + averageGrades);
        System.out.println("There are total" + countExcellentStudents + " excellent students with average grade " + averageGradesOfExcellentStudents);
        System.out.println("There are total " + countOkStudents + " OK students with average grade " + averageGradesOfOkStudents);
        System.out.println("There are total" + countFailStudents + "failure students with average grade " + averageGradesOfFailStudents);
    }
    //method to check the student grades type
    public static String studentGradeName(int studentGrade)
    {

        if (studentGrade > 89){return "Excellent";}
        if (studentGrade > 60 && studentGrade < 89){return "OK";}
        if (studentGrade < 60) {return "Failure";}
        return "Null";
    }

}

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
class Student
{
    private String studentName, grades;
    private int studentGrades;
    //method for student object
    public Student (String studName, int studGrades, String grades)
    {
        studentName = studName;
        studentGrades = studGrades;
        this.grades = grades;
    }
    //a method to print student information
    public String toString()
    {
        return studentName + "\t" + studentGrades + "\t" + grades;
    }

}
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Program Output:

StudentDatabase - StudentDatabaseDriver.java StudentDatabase src Student DatabaseDriver m main Main StudentDatabaseDriver.java students.txt Student.java } 13 //counts and totals OK students if (grades = "OK") { totalokStudents = totalokStudents + studentgrade; countOkStudents++; } //counts and totals Fail students if (grades = "Fail") totalFailStudents = totalFailStudents + studentgrade; countFailStudents++; O } Project StudentDatabase -/IdeaProjects/StudentDatabase 30 31 ► idea 32 out 33 src 34 35 Student 36 StudentDatabaseDriver 37 students.txt 38 39 1. StudentDatabase.ml 40 Milli External Libraries 41 Scratches and Consoles 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 //prints out students information System.out.println(student); totalStudents = totalStudents + studentgrade; countStudents++; //average grades are calculated here averageGrades = (double)totalStudents/countStudents; averageGradesOfExcellentStudents = (double) totalexcellentStudents/countExcellentStudents; averageGradesofokStudents = (double)totalokStudents/countOkStudents; averageGradesOfFailStudents = (double)totalFailStudents/countFailStudents; //Prints for user System.out.println("There are total " + countStudents + " students with average grade " + averageGrades); System.out.println("There are total" + countExcellentStudents + " excellent students with average grade " + averageGradesOfExcellentStu System.out.println("There are total " + countókStudents + " OK students with average grade + averageGradesofokStudents); System.out.println("There are total" + countFailStudents + "failure students with average grade " + averageGradesOfFailStudents); Run: Main x John Smith 90 Excellent Barack Obama 95 Excellent Al Clark 80 OK Sue Taylor 55 Failure Ann Miller 75 OK George Bush 58 Failure John Miller 65 OK There are total 7 students with average grade 74.0 There are total2 excellent students with average grade 92.5 There are total 3 OK students with average grade 73.33333333333333 There are totaløfailure students with average grade NaN Favorites Process finished with exit code 0 6: TODO 2. Terminal E O: Messages O Build completed successfully in 7 s 722 ms (moments ago) 4: Run Event Log 39:14 LF UTF-8 4 spaces 0