Question

Copy the entire program 9A and paste it into this one. Be sure to change the class name to 9B.

Use descriptive variable names in camel-case with the first letter in lowercase.

In the Student class, change the public attributes firstName and lastName to private ones.

In the Student class, add getters and setters called getFirstName, getLastName, setFirstName, setLastName for the two attributes.

In the Student class, add a constructor for the Student class that accepts two Strings, one parameter that you will assign to firstName and the other parameter that you will assign to lastName. If you want, you can call your parameters firstName and lastName just like the attribute names, but if you do, you will have to call your attribute names this.firstName and this.lastName within the constructor so that the compiler will know which firstName is the parameter and which is the attribute. If you call the parameters by some other names like fn and ln, or firstNameInit and lastNameInit, then you don’t have to use the “this” modifier within your constructor. Normally, fn is NOT a good variable name because it’s not very descriptive, but in a constructor, there are only a few lines of code, so it should be obvious what these short parameter names stand for, and this is common in the real world. I personally prefer something like firstNameInit, but I’m a purist.

You could set each attribute here, but it would be better to call both of your setters. Here is one of my setter calls in my constructor:

setFirstName(firstNameInit);

In main, where you called the default constructor, call your new constructor and pass firstName and lastName as arguments, then you won’t need the next two lines where you made the assignments to the attributes.

In your print method, you won’t be able to access the attributes directly anymore, so you need to comment out that line with the print statement and redo it by calling the getter methods:

System.out.printf("%2d. %s, %s\n", i+1, students[i].getLastName(), 

                  students[i].getFirstName());

Get all this working before moving on.

Now comment out the printf lines you just made and replace with this line:

System.out.printf("%2d. %s\n", i+1, students[i].toString());

Note that you only need ONE %s in the format specifier now.

Get this working before moving on.

Now comment out those lines you just made and replace with this line:

System.out.printf("%2d. %s\n", i+1, students[i]);

The reason this still works is that when you try to print something into a String, the compiler automatically checks to see whether there is a toString method for this class, and if so, it replaces it there for you.

Run it with the Sample Data and make your screen prints and the other sections of the Word file.

Please don’t stay completely stuck for much over an hour without contacting the instructor.

Sample Runs:

Please enter the maximum number of students: 8

First name (enter period . to quit): Luke

Last name: Skywalker

First name (enter period . to quit): Darth

Last name: Vader

First name (enter period . to quit): Han

Last name: Solo

First name (enter period . to quit): R2D2

Last name: Droid

First name (enter period . to quit): 3CPO

Last name: Droid

First name (enter period . to quit): .

1. Skywalker   , Luke

2. Vader       , Darth

3. Solo        , Han

4. Droid       , R2D2

5. Droid       , 3CPO

1. Droid       , 3CPO

2. Droid       , R2D2

3. Skywalker   , Luke

4. Solo        , Han

5. Vader       , Darth

Here's 9A

public class Student {
public String firstName; // first name
public String lastName; // last name

public Student(String first, String last) {
firstName = firstName;
lastName = lastName;
}

public String toString() {

return String.format ("%-12s, %-12s", firstName, lastName);

}

}

Answer 1

Student9B.java

//Program saved as Student9B
public class Student9B {
   //private member variables
   private String firstName;   
private String lastName;   
  
//constructor that sets firstname and lastname
Student9B(String firstNameInit, String lastNameInit)
{
setFirstName(firstNameInit);
setLastName(lastNameInit);
}
  
//setter methods
//method to set firstname
public void setFirstName(String firstNameInit)
{
   this.firstName = firstNameInit;
}
  
//method to set lastname
public void setLastName(String lastNameInit)
{
   this.lastName = lastNameInit;
}
  
//getter methods
//method that returns firstname
public String getFirstName()
{
   return this.firstName;
}
//method that returns lastname
public String getLastName()
{
   return this.lastName;
}
  
public void sort(Student9B[] students,int count)
{
   //loop through the students array
           for(int i=0;i<=count;i++)
           {
               for(int j=i+1;j<=count-1;j++)
               {
                   //comparing the elements
                   int result = students[i].getLastName().compareTo(students[j].getLastName());
                   if(result>0){
                       //swapping in array
                       Student9B temp=students[i];
                       students[i]=students[j];
                       students[j]=temp;
                   }

               }

           }
}
  
//override toString method
public String toString() {
return String.format ("%-12s, %-12s", getLastName(), getFirstName());
  
}
}

Student9BDriver.java

import java.util.Scanner;

public class Student9BDriver {

   public static void main(String[] args) {
       Scanner input=new Scanner(System.in);
       String firstName,lastName;
       boolean repeat = true;
       int maxStudents;

       //prompt and read maximum number of students
       System.out.print("Please enter the maximum number of students: ");
       maxStudents = input.nextInt();

       //create an array of student objects
       Student9B[] students = new Student9B[maxStudents];
       input.nextLine();
       int count=0;

       //read the data from the user until the maximum nuber is reached or the user quits
       do
       {
           //prompt and read firstname
           System.out.print("First name (enter period . to quit): ");
           firstName = input.nextLine();
           //if user entered '.' exit the loop by setting repeat to false
           if(firstName.equals("."))
           {
               repeat = false;
           }
           else
           {
               //else prompt and read the lastname
               System.out.print("Last name: ");
               lastName = input.nextLine();
               //set the firstname and lastname to the object at index count
               students[count] = new Student9B(firstName, lastName);
               count++; //increment count, count will have actual number of data inserted
           }
       }while(repeat && count<maxStudents);

       System.out.println();
       //print the students names
       for(int i=0;i<count;i++ )
       {
           System.out.printf("%2d. %s\n", i+1, students[i]);
       }

       //sort the students based on last name
       sortStudentNames(students, count);
       System.out.println();

       //print the sorted list of students
       for(int i=0;i<count;i++ )
       {
           System.out.printf("%2d. %s\n", i+1, students[i].toString());
       }
       input.close();
   }

   //method that takes the students names and sorts them
   public static void sortStudentNames(Student9B[] students,int count)
   {
       //loop through the students array
       for(int i=0;i<=count;i++)
       {
           for(int j=i+1;j<=count-1;j++)
           {
               //comparing the students based on lastname
               int res = students[i].getLastName().compareTo(students[j].getLastName());
               if(res>0)
               {
                   //swap the students
                   Student9B temp=students[i];
                   students[i]=students[j];
                   students[j]=temp;
               }

           }

       }
   }

}

Output:

Console X <terminated> Student9BDriver [Java Application] C:\Program Files\N Please enter the maximum number of students: 8 First name (enter period . to quit): Luke Last name: Skywalker First name (enter period . to quit): Darth Last name: Vader First name (enter period . to quit): Han Last name: Solo First name (enter period . to quit): R2D2 Last name: Droid First name (enter period . to quit): 3CPO Last name: Droid First name (enter period. to quit): 1. Skywalker , Luke 2. Vader 3. Solo 4. Droid 5. Droid Darth Han , R2D2 , 3CPO 1. Droid 2. Droid 3. Skywalker, Luke 4. Solo 5. Vader , R2D2 , ЗСРО Han , Darth