Question

Convert this java code from hashmap into arraylist.
import java.io.*;
import java.util.*;

public class Solution {

        public static void main(String[] args) throws IOException {

                Scanner sc = new Scanner(System.in);
                HashMap labs = new HashMap();

                while (true) {
                        System.out.println("Choose operation : ");
                        System.out.println("1. Create a Lab");
                        System.out.println("2. Modify a Lab");
                        System.out.println("3. Delete a Lab");
                        System.out.println("4. Assign a pc to a Lab");
                        System.out.println("5. Remove a pc from a Lab");
                        System.out.println("6. Quit");

                        int choice = sc.nextInt();
                        String name=sc.nextLine();
                        switch (choice) {
                        case 1:
                                System.out.println("Enter Lab name (i.e. LAB A or LAB B) : ");
                                name = sc.nextLine();
                                labs.put(name, new Lab(name));
                                break;
                        case 2:
                                System.out.println("Enter name of lab to modify : ");
                                name = sc.nextLine();
                                
                                if (labs.containsKey(name)) {
                                        System.out.println("Enter new name to modify : ");
                                        String name2 = sc.nextLine();
                                        Lab lab = labs.get(name);
                                        labs.remove(name);
                                        labs.put(name2, lab);
                                } else {
                                        System.out.println("Invalid name");
                                }

                                break;
                        case 3:
                                System.out.println("Enter name of lab to delete : ");
                                name = sc.nextLine();
                                if (labs.containsKey(name)) {
                                        Lab lab = labs.get(name);
                                        System.out.println("Total pc in this lab are : " + lab.pc_count);
                                        labs.remove(name);
                                } else {
                                        System.out.println("Invalid name");
                                }
                                break;
                        case 4:
                                System.out.println("Enter name of lab to assign a pc : ");
                                name = sc.nextLine();
                                if (labs.containsKey(name)) {
                                        if (labs.get(name).pc_count >= 50) {
                                                System.out.println("cannot assign more pc");
                                        } else {
                                                labs.get(name).pc_count++;
                                        }
                                } else {
                                        System.out.println("Invalid name");
                                }
                                break;
                        case 5:
                                System.out.println("Enter name of lab to assign a pc : ");
                                name = sc.nextLine();
                                if (labs.containsKey(name)) {
                                        if (labs.get(name).pc_count <= 0) {
                                                System.out.println("cannot remove pc");
                                        } else {
                                                labs.get(name).pc_count--;
                                        }
                                } else {
                                        System.out.println("Invalid name");
                                }
                                break;
                        case 6:
                                return;
                        default:
                                System.out.println("Invalid choice choose again.");
                                break;
                        }
                }

        }

        static class Lab {
                String name;
                int pc_count;

                Lab(String name) {
                        this.name = name;
                        pc_count = 0;
                }
        }
}

Answer 1

THE CODE IS:

import java.io.IOException;
import java.util.ArrayList;
import java.util.Scanner;

public class Solution {

    // In stead of hashmap we will use two arraylist.
    // One arraylist of type String to act as the Key arraylist
    // Second arraylist to store the Lab to act as the Value arraylist
    static ArrayList<String> key = new ArrayList<>();
    static ArrayList<Lab> value = new ArrayList<>();

    public static void put(String name, Lab lab) {
        // if key is already there in hashmap then replace the previous lab value
        if (key.contains(name)) {
            int index = key.indexOf(name);
            value.set(index, lab);
        }// else if key is not present then add the key-value pair to the hashmap
        else {
            key.add(name);
            value.add(lab);
        }
    }

    public static void main(String[] args) throws IOException {

        Scanner sc = new Scanner(System.in);

        while (true) {
            System.out.println("Choose operation : ");
            System.out.println("1. Create a Lab");
            System.out.println("2. Modify a Lab");
            System.out.println("3. Delete a Lab");
            System.out.println("4. Assign a pc to a Lab");
            System.out.println("5. Remove a pc from a Lab");
            System.out.println("6. Quit");

            int choice = sc.nextInt();
            String name = sc.nextLine();
            switch (choice) {
                case 1:
                    System.out.println("Enter Lab name (i.e. LAB A or LAB B) : ");
                    name = sc.nextLine();
                    put(name, new Lab(name));
                    break;
                case 2:
                    System.out.println("Enter name of lab to modify : ");
                    name = sc.nextLine();

                    if (key.contains(name)) {
                        System.out.println("Enter new name to modify : ");
                        String name2 = sc.nextLine();
                        // getting index of current position of key and updating the name
                        int index = key.indexOf(name);
                        key.set(index, name2);
                    } else {
                        System.out.println("Invalid name");
                    }

                    break;
                case 3:
                    System.out.println("Enter name of lab to delete : ");
                    name = sc.nextLine();
                    if (key.contains(name)) {
                        // getting lab
                        int index = key.indexOf(name);
                        Lab lab = value.get(index);
                        System.out.println("Total pc in this lab are : " + lab.pc_count);
                        // removing the lab from the hashmap
                        key.remove(index);
                        value.remove(index);
                    } else {
                        System.out.println("Invalid name");
                    }
                    break;
                case 4:
                    System.out.println("Enter name of lab to assign a pc : ");
                    name = sc.nextLine();
                    if (key.contains(name)) {
                        // checking if number of pc in the lab exceeds 50
                        if (value.get(key.indexOf(name)).pc_count >= 50) {
                            System.out.println("cannot assign more pc");
                        }// if it doesn't then increment the value of pc in the lab
                        else {
                            value.get(key.indexOf(name)).pc_count++;
                        }
                    } else {
                        System.out.println("Invalid name");
                    }
                    break;
                case 5:
                    System.out.println("Enter name of lab to remove a pc : ");
                    name = sc.nextLine();
                    if (key.contains(name)) {
                        if (value.get(key.indexOf(name)).pc_count <= 0) {
                            System.out.println("cannot remove pc");
                        } else {
                            value.get(key.indexOf(name)).pc_count--;
                        }
                    } else {
                        System.out.println("Invalid name");
                    }
                    break;
                case 6:
                    return;
                default:
                    System.out.println("Invalid choice choose again.");
                    break;
            }
        }

    }

    static class Lab {

        String name;
        int pc_count;

        Lab(String name) {
            this.name = name;
            pc_count = 0;
        }
    }
}