Question

In java. Using a linked list only, iterator and scanner.

Develop a program to maintain a Linked List of homework assignments name and due date. When an assignment is assigned, add it to the list, and when it is completed, remove it. You should keep track of the due date. Your program should provide the following services each contained within its own method:

• Add a new assignment. (3 pts)
• Remove an assignment. (3pts)
• Provide a list of the assignments in the order they were assigned. (3pts)
• Find the assignment(s) with the earliest due date (3pts)

Answer 1

code in java with explanation in comments

import java.util.*;
import java.text.*; 
class Test{
    //static helper method to print menu
    public static void print_menu(){
        System.out.println("Select an option.");
        System.out.println("1. Add a new assignment");
        System.out.println("2. Remove an assignment");
        System.out.println("3. List assignment in order they were assigned");
        System.out.println("4. Assignment with earliest due date");
        System.out.println("0. Exit");
    }
    public static void main(String[] args) throws Exception{
        //linked list to store assignment name
        LinkedList<String> homeworkAssignmentsName = new LinkedList<String>();
        //linked list to store assignment due date
        LinkedList<Date> homeworkAssignmentsDueDate = new LinkedList<Date>();
        //Scanner class to take input
        Scanner sc = new Scanner(System.in);
        //declare variable to read from user
        String name, dateString;
        Date date;
        //Dateformatter to convert entered date to date class
        DateFormat formatter = new SimpleDateFormat("ddMMyyyy");
        int op;
        //Menu driven program
        do{
            //print menu
            print_menu();
            //take input from user
            op = sc.nextInt();
            //check for invalid input
            if(op<0||op>4){
                 System.out.println("Invalid Input\nPlease select an option from 0 to 4 only");
            }
            //perform different operations depending on input
            switch(op){
                case 1: {
                    //take input for new assignment to add
                    System.out.print("Enter name of assignment: ");
                    name=sc.next();
                    System.out.print("Enter due date (ddMMyyyy): ");
                    dateString=sc.next();
                    date = formatter.parse(dateString);
                    //add new assignment to our linked list
                    homeworkAssignmentsName.add(name);
                    homeworkAssignmentsDueDate.add(date);
                    break;
                }
                case 2: {
                     //take input for assignment to remove
                    System.out.print("Enter name of assignment to remove: ");
                    name=sc.next();
                    //search for the assignment in our list
                    int index = homeworkAssignmentsName.indexOf(name);
                    if(index==-1){
                        //display message if not found
                        System.out.println("Assignment not found!");
                    }else{
                        //delete both assignment and due date if found
                        homeworkAssignmentsName.remove(index);
                        homeworkAssignmentsDueDate.remove(index);
                        System.out.println("Assignment deleted.");
                    }
                    break;
                }
                case 3: {
                    //declare iterators to traverse in the linked list
                    Iterator it1 = homeworkAssignmentsName.iterator();
                    Iterator it2 = homeworkAssignmentsDueDate.iterator();
                    System.out.println("Assignments: Name  -  Date");
                    //traverse both list and print on console
                    while(it1.hasNext()){
                        System.out.println(it1.next() + "  -  " + it2.next());
                    }
                    break;
                }
                case 4:{
                    //declare iterators to traverse in the linked list
                    Iterator it = homeworkAssignmentsDueDate.iterator();
                    //check if there are no assignments and display error
                    if(!it.hasNext()){
                        System.out.println("No assignments added!");
                    }
                    else{
                        //initialize d with first value to compare
                        Date d = (Date)it.next();
                        //compare d with all other dates and store least date
                        while(it.hasNext()){
                            Date x = (Date)it.next();
                            if(d.after(x)){
                                d=x;
                            }
                        }
                        //search for assignment with this date
                        int index = homeworkAssignmentsDueDate.indexOf(d);
                        //display in console
                        System.out.println("Assignments with least due date is : " + homeworkAssignmentsName.get(index) + "  -  " + d);
                    } 
                    break;
                }
            }
        }while(op!=0);
    }   
}

Code Screenshot

Console Output Screenshot

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