Question

USE JAVA. Write a very general sort method that can sort any type of data arrays/lists. For example, can sort a list of integers in ascending order, a list of integers in descending order, a list of doubles, a list of student objects (with names and scores) in ascending order of names, or in descending order of scores, … You can use any pre-defined sort function or can code your own. Use your favorite language for implementation. If your language doesn’t support these features, implement a revised version (clearly state the revision you made to the problem with a brief discussion of the language’s weakness.) Then test the following cases: (a) 4, 3, 7, 2, 1, 9 in ascending order (b) 4.5, 2.0, 9.0, 8.4, 7.2, 6.1, 20.5, 2.1 in descending order (c) John 40, Casey 45, Ben 47, Zadi 41, Kay 39, Tay 43 in ascending order of names (d) John 40, Casey 45, Ben 47, Zadi 41, Kay 39, Tay 43 in descending order of scores Include your program source code and test cases (may copy paste output or show screenshots) as answer to any coding problem. Use Java.

Answer 1

I have created a MENU DRIVEN program in java with the following menu:-
***MENU FOR SORTING***
1. Sort list of integers in ascending order
2. Sort list of integers in descending order
3. Sort list of doubles in ascending order
4. Sort list of doubles in descending order
5. Sort student objects in ascending order of their names
6. Sort student objects in descending order of their scores

There are comments in those lines which could have been difficult to understand for you. In case of any confusion, fell free to ask in the comments down below.

For the first four options, I have used built-in functions for sorting and printed the ouput using System.out.print() statement. For options 5 and 6 I have used Comparator Interface to successfully compare and sort the objects of type Student. Comparator interface is used to order the objects of user-defined classes. A comparator object is capable of comparing two objects of two different classes. In this program, we have created an List and called Comparator using Collections. the Java collections framework is a set of classes and interfaces that implement commonly reusable collection data structures.

note:- copy the code and save the file with name "sort.java" to successfully compile and run the program.

Here is the code for the same :-

//import Arrays, List, Collections
import java.util.*;

// A class to represent a student.
class Student {
    int score;
    String name;
    // Constructor
    public Student(int score, String name) {
        this.score = score;
        this.name = name;
    }

    //getter and setter methods
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getscore() {
        return score;
    }

    public void setscore(Integer score) {
        this.score = score;
    }
    // Used to print student details in main()
    public String toString()
    {
        return this.name+ " "+this.score;
    }
}   //class Student ends here

class Sortbyname implements Comparator<Student>{
    // Used for sorting in ascending order of roll number
    public int compare(Student a, Student b) {
        return a.name.compareTo(b.name);
    }
} //Sortbyname ends here

class SortbyScore implements Comparator<Student>
{
    // Used for sorting in descending order of score
    public int compare(Student a, Student b)
    {
        return a.score - b.score;
    }
} //SortbyScore ends here

public class sort{
    public static void main(String args[])
    {
        final Scanner scr=new Scanner(System.in); //for taking input from the user
        char ch='y';   //Loop variable

        do{
            //Menu for the program
            System.out.println("***MENU FOR SORTING***");
            System.out.println("1. Sort list of integers in ascending order");
            System.out.println("2. Sort list of integers in descending order");
            System.out.println("3. Sort list of doubles in ascending order");
            System.out.println("4. Sort list of doubles in descending order");
            System.out.println("5. Sort student objects in ascending order");
            System.out.println("6. Sort student objects in descending order");
            System.out.print("Enter Your Choice: ");
            //Read input from user and parse it to type int and store as choice
            int choice=scr.nextInt();

            System.out.println(""); //For proper formatting

            switch(choice)
            {
                case 1: //Sort list of integers in ascending order
                int n1;
                System.out.print("Enter no. of elements you want in integer array:");
                n1 = scr.nextInt();
      
                int a1[] = new int[n1];
                System.out.println("Enter all the elements:");
                for (int i = 0; i < n1; i++){
                    a1[i] = scr.nextInt();
                }
              
                Arrays.sort(a1); //sort using built in function
       
                System.out.print("Ascending Order of integer array:");
                for (int i = 0; i < n1 ; i++){
                    System.out.print(a1[i] + ",");
                }        
                    break;
          
                case 2: //Sort list of integers in descending order
                int n2, temp;
                System.out.print("Enter no. of elements you want in integer array:");
                n2 = scr.nextInt();
      
                int a2[] = new int[n2];
                System.out.println("Enter all the elements:");
                for (int i = 0; i < n2; i++)
                {
                    a2[i] = scr.nextInt();
                }
              
                //Sort the array in descending order  
                for (int i = 0; i < n2; i++) {   
                    for (int j = i+1; j < n2; j++) {   
                        if(a2[i] < a2[j]) {  
                            temp = a2[i];
                            a2[i] = a2[j];  
                            a2[j] = temp;  
                        }   
                    }   
                }
       
                System.out.print("Descending Order of integer array:");
                for (int i = 0; i < n2 ; i++){
                    System.out.print(a2[i] + ",");
                }             
                    break;

                case 3: //Sort list of doubles in ascending order
                int n3;
                System.out.print("Enter no. of elements you want in double array:");
                n3 = scr.nextInt();
      
                double a3[] = new double[n3];
                System.out.println("Enter all the elements:");
                for (int i = 0; i < n3; i++) {
                    a3[i] = scr.nextDouble();
                }
              
                Arrays.sort(a3); //sort using built in function
       
                System.out.print("Ascending Order of double array:");
                for (int i = 0; i < n3 ; i++){
                    System.out.print(a3[i] + ",");
                }
                        break;
              
                case 4: //Sort list of doubles in descending order
                int n4;
                double temp1;
                System.out.print("Enter no. of elements you want in double array:");
                n4 = scr.nextInt();
      
                double a4[] = new double[n4];
                System.out.println("Enter all the elements:");
                for (int i = 0; i < n4; i++){
                    a4[i] = scr.nextDouble();
                }
              
                //Sort the array in descending order  
                for (int i = 0; i < n4; i++) {   
                    for (int j = i+1; j < n4; j++){
                        if(a4[i] < a4[j]) {  
                            temp1 = a4[i];
                            a4[i] = a4[j];
                            a4[j] = temp1;  
                        }   
                    }   
                }
       
                System.out.print("Descending Order of double array:");
                for (int i = 0; i < n4 ; i++){
                    System.out.print(a4[i] + ",");
                }
                    break;

                case 5: //Sort student objects in ascending order of their names
                //creating object of type Student
                List<Student> ar= new ArrayList<>() ;
                System.out.println("Enter the number of students: ");
                int n5= scr.nextInt();

                for(int i=0; i<n5; i++){
                    /*consuming the leftover new line using the nextLine() method to avoid errors*/
                    scr.nextLine();
                    System.out.println("Enter name of new student: ");
                    String name= scr.nextLine();
                    System.out.println("Enter score of this student: ");
                    int score= scr.nextInt();

                    //allocating memory and initializing
                    Student obj= new Student(score, name);
                    ar.add(obj); //adding object to List
                }

                //Built-in function to sort
                Collections.sort(ar, new Sortbyname());
                System.out.println("\nSorted by name in ascending order");
                for (int i=0; i<ar.size(); i++)
                System.out.println(ar.get(i));
                    break;

                case 6: //Sort student objects in descending order of their scores
                 //creating object of type Student
                 List<Student> ls= new ArrayList<>() ;
                 System.out.println("Enter the number of students: ");
                 int n6= scr.nextInt();

                 for(int i=0; i<n6; i++){
                     /*consuming the leftover new line using the nextLine() method to avoid errors*/
                     scr.nextLine();
                     System.out.println("Enter name of new student: ");
                     String name= scr.nextLine();
                     System.out.println("Enter score of this student: ");
                     int score= scr.nextInt();

                     //allocating and initializing
                     Student obj= new Student(score, name);
                     ls.add(obj); //add object to List
                 }

                 //Built-in function to sort
                 Collections.sort(ls, new SortbyScore());
                 //Built-in function to reverse
                 Collections.reverse(ls);
                 //printing the values in descending
                 System.out.println("\nSorted by score in descending order");
                 for (int i=0; i<ls.size(); i++)
                 System.out.println(ls.get(i));
                    break;

                default:
                        System.out.println("Wrong choice!!! Try again...");
            }

            System.out.println(""); //For proper formatting
            System.out.print("Want to enter more? (y/n): ");
            ch=scr.next().charAt(0); //Read next char from user

            System.out.println(""); //For proper formatting
        }while(ch=='y' || ch=='Y');

        System.out.println("Exiting the Program...");
        scr.close(); //closing scanner object

    }   //main() ends here
  
}   //class sort ends here

The ouput for test cases are as follows:-

(a)

(b)

(c)

(d)

Ask doubts in comment section.

Happy Learning..

.