Question

How would you make it hold both the student's name and their teacher? then be able to sort based on either the students name or who their teacher is?

import java.util.Scanner; //for taking user input

public class StudentName{ //you can change class name

public static void main(String[] args);

{

Scanner in = new Scanner(System.in);

//finding length of array studentNames

System.out.print("how many students? :") ;

int totalStudents = in. nextInt() ;

String[] studentNames = new String[totalStudents] ;

//input user name

for(int j=0;j<studentNames.length;j++)

{

System. out. println(j) ;

System. out.print("enter student name:") ;

studentNames[j]=in.nextline();

}

for (String element : studentName)

{

System. out. println(element) ;

}

}

Answer 1

Code:

import java.util.Scanner;
import java.util.Arrays;
class Student
{
   // Class variables for student and their teacher names
   public String studentName;
   public String teacherName;
  
   // Constructor parameters
   Student(String studentName,String teacherName)
   {
       this.studentName = studentName;
       this.teacherName = teacherName;
   }
  
   public String toString()
   {
       return "Student:" + studentName + " Teacher:" + teacherName;
   }
  
   void setStudentName(String newStudentName)
   {
       studentName = newStudentName;
   }
  
   void setTeacherName(String newTeacherName)
   {
       teacherName = newTeacherName;
   }
  
}

// An class of Generic Type
class CustomArrayList<E>
{
   // This variable is used to create an Array of type object of size initial list capacity
   private static final int INITIAL_LIST_CAPACITY = 5;
   // An array of type Object
   private Object data[] = {};
   // This variable is used to store the size of the custom arrayList
   private int size = 0;
  
   // Constructor
   public CustomArrayList()
   {
       // Initializing the array with size of initial list capacity
       data = new Object[INITIAL_LIST_CAPACITY];
   }
  
   // An method to add values to the custom arrayList
   public void add(E e)
   {
       // If there is no space to add values to the arrayList, double the size of the arrayList
       if(size == data.length)
       {
           increaseCapacity();
       }
      
       // Adding the value to the arrayList
       data[size++] = e;
   }
  
   @SuppressWarnings("unchecked")
   public E get(int index)
   {
       if ( index <0 || index>= size)
       {
           throw new IndexOutOfBoundsException("Index: " + index + ", Size " + index);
       }
       return (E) data[index];
   }
  
   public void set(int index,Student s)
   {
       if ( index <0 || index>= size)
       {
           throw new IndexOutOfBoundsException("Index: " + index + ", Size " + index);
       }
      
       data[index] = s;
   }
  
   // An method to remove values from the custom arrayList
   public Object remove(int index)
   {
       // If the value of the index is 0 or negative
       if(index < 0 || index >= size)
       {
           // Throw an IndexOutOfBoundsException if the index is invalid
           throw new IndexOutOfBoundsException("Index: " + index + ", Size " + index);
       }
      
       Object removedElement = data[index];
      
       // Update the list
       for(int i = index;i<size-1;i++)
       {
           data[i] = data[i+1];
       }
      
       // Decrementing the size of the list by 1
       size--;
      
       // Returning the removed element
       return removedElement;
   }
  
   // An method to increase the list capacity
   private void increaseCapacity()
   {
       // Calculating the new capacity
       int newIncreasedCapacity = data.length * 2;
       // Updating the list
       data = Arrays.copyOf(data, newIncreasedCapacity);
   }
  
   // Displaying the elements of the list
   public void display()
   {
       // Printing the elements of the list
       for(int i=0;i<size;i++)
       {
           System.out.println(data[i]);
       }
   }
}

public class StudentData2
{
   // QuickSort where the comparison is based on student name
   static int QuickSortStudentName(CustomArrayList<Student> s, int low, int high)
{
Student pivot_data = s.get(high);
       // index of smaller element
int i = (low-1);
for (int j=low; j<high; j++)
{
              
           if ( s.get(j).studentName.compareTo(pivot_data.studentName) <=0)
           {
               i++;
               // swap student objects at index i and j
               Student temp = new Student(s.get(i).studentName,s.get(i).teacherName);
               s.set(i,s.get(j));
               s.set(j,temp);
           }              

}

  // swap student objects at index i+1 and high
       Student temp = new Student(s.get(i+1).studentName,s.get(i+1).teacherName);
       s.set(i+1,s.get(high));
       s.set(high,temp);
return i+1;
}
  
// QuickSort where the comparison is based on student name
   static int QuickSortTeacherName(CustomArrayList<Student> s, int low, int high)
{
       Student pivot_data = s.get(high);
       // index of smaller element
int i = (low-1);
       // Sort based on teacher name
       for (int j=low; j<high; j++)
{
           if ( s.get(j).teacherName.compareTo(pivot_data.teacherName) <=0)
           {
               i++;
               // swap student objects at index i and j
               Student temp = new Student(s.get(i).studentName,s.get(i).teacherName);
               s.set(i,s.get(j));
               s.set(j,temp);
           }
              
       }
       // swap student objects at index i+1 and high
       Student temp = new Student(s.get(i+1).studentName,s.get(i+1).teacherName);
       s.set(i+1,s.get(high));
       s.set(high,temp);
       return i+1;
   }
  
   static void sort(CustomArrayList<Student> s, int low, int high,int choice)
{
       if(choice==1)
       {
           if (low < high)
           {
               /* pi is partitioning index, Student object at index pi is now at right place */
               int pi = QuickSortStudentName(s, low, high);
  
               // Recursively sort elements before
               // partition and after partition
               sort(s, low, pi-1,1);
               sort(s, pi+1, high,1);
           }
       }
      
       else if(choice==2)
       {
           if (low < high)
           {
               /* pi is partitioning index, Student object at index pi is now at right place */
               int pi = QuickSortTeacherName(s, low, high);
  
               // Recursively sort elements before
               // partition and after partition
               sort(s, low, pi-1,2);
               sort(s, pi+1, high,2);
           }          
       }
}  
  
   public static void main(String[] args)
   {
       // Creating an object of Custom arrayList
       CustomArrayList<Student> students = new CustomArrayList<Student>();
      
       // Scanner object which is used to read inputs
       Scanner in = new Scanner(System.in);
       // Prompting the user to enter number of students data to be entered
       System.out.print("how many students?:");
       // Reading the input
       int totalStudents = Integer.parseInt(in.nextLine());
      
       // This for loop is iterated totalStudents times
       for(int j = 0; j<totalStudents;j++)
       {
           // Prompting the user to enter student name
           System.out.printf("Enter name of student %d:",j+1);
           // Reading the student name
           String studentName = in.nextLine();
           // Prompting the user to enter teacher name
           System.out.printf("Enter name of the teacher for student %d:",j+1);
           // Reading the teacher name
           String teacherName = in.nextLine();
          
           // Adding the data to the custom arrayList
           students.add(new Student(studentName,teacherName));
       }
      
       // Prompting the user to enter their choice for sort
       System.out.println("Enter 1 to sort the array based on student name");
       System.out.println("Enter 2 to sort the array based on teacher name");
       System.out.print("Enter your choice:");
      
       // Reading the choice
       int choice = in.nextInt();
      
       // If choice is 1
       if(choice==1)
       {
           // Sort the array based on student name
           sort(students,0,totalStudents-1,1);
           System.out.println("The array after sort based on student name:");
       }
      
       // If choice is 2
       else if(choice==2)
       {
           // Sort the array based on teacher name
           sort(students,0,totalStudents-1,2);
           System.out.println("The array after sort based on teacher name:");
       }
      
       // If the choice is not either 1 or 2
       else
       {
           System.out.println("Invalid choice");
           // Terminating the program
           System.exit(0);
       }
students.display();
   }
}

OUTPUT: