New variable for each user input in a loop

Question

I am currently working on a program that takes a user input of the number of students in a class, then, (in a while loop), takes a user input of a student number and their average grade, then, after calculation, prints the highest mark, lowest mark, and average mark of the class.

This is what I have done so far:

import java.util.Scanner;
public class ClassMarks {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.println("Enter number of students in class: ");
        int students = input.nextInt();
        int x = students;
        while (x > 0) {
            System.out.println("Enter student number: ");
            double studentNumber = input.nextDouble();
            System.out.println("Enter student grade: ");
            double studentGrade = input.nextDouble();
            x = x - 1;
        }
    }
}

I am looking for a way to get the program to create a new variable for me that stores each new user input student grade inside the while loop. ex) studentGrade1, studentGrade2, studentGrade3 ...

@radoh +1 actually, storing is not necessary. The OP can also keep the highest mark, the lowest mark and the sum of the marks. — Arnaud Denoyelle
– Arnaud Denoyelle, Commented Feb 6, 2016 at 23:04
@ArnaudDenoyelle yup, I've just added such answer/suggestion — radoh
– radoh, Commented Feb 6, 2016 at 23:07

radoh · Accepted Answer · 2016-02-06 23:06:21Z

5

Before the while loop, create variables highest/lowest grades

double highestGrade = Double.MIN_VALUE, lowestGrade = Double.MAX_VALUE;
double gradeSum = 0;

Then as you loop through the values, adjust the variables appropriately, e.g.

if (studentGrade > highestGrade)
    highestGrade = studentGrade;
if (studentGrade < lowestGrade)
    lowestGrade = studentGrade;
gradeSum += studentGrade;

And then after the loop finishes, get the average like this

double averageGrade = gradeSum / students;

answered Feb 6, 2016 at 23:06

radoh

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3 Comments

Arnaud Denoyelle Over a year ago

highestGrade = Math.max(studentGrade, highestGrade) would be nicer :) Same for lowestGrade.

radoh Over a year ago

Nicer, true, but it would mean rewriting the variable on every loop, even when the value doesn't change. Hmmm, dilemma... :)

ScopeY Over a year ago

Ohhhhh... You're right, a list isn't required. Thank you!

Salih Erikci · Accepted Answer · 2016-02-06 23:31:11Z

0

How about using a List.

List<Student> students = new ArrayList<>()

and in while loop

create a student update its fields then add it to the list

Student myNewStudent = new Student();
// update fields 

students.add(myNewStudent);

To iterate the list you can use a for loop.

for (Student s : students) { 
    // Get student info
}

Adapting this into your code:

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class ClassMarks {
// Create an inner class Student

    public static class Student {

        public double studentNumber;
        public double studentGrade;
    }

    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);
        System.out.println("Enter number of students in class: ");
        int students = input.nextInt();
        int x = students;

        // Create a list to hold your students
        List<Student> studentsList = new ArrayList<>();

        while (x > 0) {
            Student myNewStudent = new Student();
            System.out.println("Enter student number: ");
            myNewStudent.studentNumber = input.nextDouble();
            System.out.println("Enter student grade: ");
            myNewStudent.studentGrade = input.nextDouble();

            // update fields 
            studentsList.add(myNewStudent);

            x = x - 1;
        }

        // Loop your student List
        for (Student s : studentsList) {
            // Get student info
            System.out.println("Student number is: "+s.studentNumber+" grade is : "+s.studentGrade);
        }
    }
}

edited Feb 6, 2016 at 23:31

answered Feb 6, 2016 at 22:58

Salih Erikci

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3 Comments

ScopeY Over a year ago

How would I then refer back to the variables when I need to do the calculations for average grade for example?

Salih Erikci Over a year ago

all the students will be in "students" list. you can refer them as for example students.get(0)

OneCricketeer Over a year ago

@ScopeY for (Student s : students) { (do something here) }

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