Using the while Looping (Repetition) Structure Design and write code for the Jav

ID: 3561525 • Letter: U

Question

Using the while Looping (Repetition) Structure

Design and write code for the Java programs that use while loops.

1. a. Design a Java program that asks for the number of students registered in a course. The user should be prompted to enter the number of students enrolled in a course. If the number of students is greater than 0, use a counter-controlled while loop to prompt the user to enter the names of the students registered for the class. Create an output file that contains the names of the students in the class. Display a message to the user when the program is complete.

Following is a copy of the screen results that might appear after running your program, depending on the data entered. The input entered by the user is in bold. This program asks the user to enter the number and names of students in a course.

How many students are registered for this class? 10

Enter the student's name: George Smith

Enter the student's name: Elaine Sanders

Enter the student's name: Jack Cunningham

Enter the student's name: Susie Brown

Enter the student's name: Marvella Garcia

Enter the student's name: Tony Peterson

Enter the student's name: John Jones

Enter the student's name: Mary Evans

Enter the student's name: Nancy Drew

Enter the student's name: Lola Zapata

The class is full.

Write your design in the following space. Your design should be a list of Java comments without any code.

b. Write a Java program based on the design you created in Exercise 1a.Enter your program and name it Roster1.java. Name your output file student1.dat.

Step through your code by hand and complete a memory chart showing what occurs in memory when the Java code is executed.

To fill out the memory chart for each variable, specify the name of the variable, its data type, the line number in which the variable is assigned its initial value, the initial value assigned to the variable, and the line numbers in which the variable

Explanation / Answer

Design -

/*
* Declare variable to store number of students noofstudents
* Prompt user for number of students and store entered value in noofstudents
* declare an array of size noofstudents
* run a while loop for noofstudents
* in loop prompt user to enter student name and store in array
* after loop ends check if user has entered same number of namse as noofstudents
* if yes print message class is full
* use a loop to iterate through array and create a output file
*/

Code-

import java.io.PrintWriter;
import java.util.Scanner;

public class Roster1 {
    public static void main(String Args[])
    {
        int noofstudents=0;
        try
        {
            System.out.println("How many students are registered for this class?");
            Scanner objscan=new Scanner(System.in);
            noofstudents = objscan.nextInt();

            int i=0;
            String[] arrStudents=new String[noofstudents];
            while(i<noofstudents)
            {
                System.out.println("Enter the student's name: ");
                arrStudents[i] = objscan.next();
                i++;
            }
            if(i>=noofstudents)
                System.out.println("The class is full");

            PrintWriter writer = new PrintWriter("student1.dat", "UTF-8");
            i=0;
            while(i<noofstudents)
            {
                writer.println((i+1) + " ." + arrStudents[i]);
                i++;
            }
            writer.close();
        }
        catch(Exception e)
        {
            System.out.println("Error in operation: "+e.getMessage());
        }
    }

}

output-

How many students are registered for this class?
2
Enter the student's name:
rtyh
Enter the student's name:
yusgdf
The class is full

Variable name

Data type

Declaration line number

Initialization line number

Initial

Change

value

line number

noofstudents

int

21,28,32

arrStudents

String[]

null