Remove element of arraylist from user input without using iteratior

Question

I need to remove any element of ArrayList, from user input and without using java iterator:

(see (switch) case 2:)

when I select Option 2 and proceed to input a name, for example James, it wont do anything as the list of friends would be the same. Any help would be much appreciated!

import java.util.Scanner;
import java.util.ArrayList;

public class FriendsTest
{
   public static void main(String[] args)
   {
      Scanner input = new Scanner(System.in);

      // objects
      ArrayList<Friends> friendsList = new ArrayList<>();

      Friends a1 = new Friends("James", 10);
      Friends a2 = new Friends("Christopher", 17);
      Friends a3 = new Friends("George", 25);
      Friends a4 = new Friends("Linda", 31);
      Friends a5 = new Friends("Karen", 62);

      friendsList.add(a1);
      friendsList.add(a2);
      friendsList.add(a3);
      friendsList.add(a4);
      friendsList.add(a5);

      // menu

      int menu_choice;

      String name;
      int age;

      do
      {
         System.out.println("\n1. Add a Friend");
         System.out.println("2. Remove a Friend");
         System.out.println("3. Display all Friends");
         System.out.println("4. Exit\n");

         System.out.print("\nSelect one option: ");
         menu_choice = input.nextInt();

         switch (menu_choice)
         {
            case 1:
               System.out.print("Enter Friend's name: ");
               name = input.next();

               System.out.print("Enter Friend's age: ");
               age = input.nextInt();

               Friends a6 = new Friends(name, age);
               friendsList.add(a6);
               break;

            case 2:
               System.out.print("Enter Friend's name to remove: ");
               name = input.next();

               friendsList.remove(name);
               break;

            case 3:
               for(int k = 0; k < friendsList.size(); k++)
               {
                  System.out.println(friendsList.get(k).name + " " + friendsList.get(k).age);
               }
               break;

            case 4:
               System.exit(0);

         }//end switch        



      } while (menu_choice != 4);


   }//end main



}//end class

Update with my constructor and methods class

public class Friends 
   {
      public String name;
      public int age;

      // parameters
      public Friends(String _name, int _age)
      {
         name = _name;
         age = _age;
      }

       // set name
       public void setName(String friendName)
       {
          name = friendName;
       }

       // get name
       public String getName()
       {
          return name;
       }

       // set age
       public void setAge(int friendAge)
       {
          age = friendAge;
       }

       // get age
       public int getAge()
       {
          return age;
       }

       // return toString()
       public String toString()
       {
       return getName() + " " + getAge();
       }

    } //end clas

The problem is that you're trying to remove a string from an ArrayList of objects that are very much not strings. You'll need to identify which item has the name entered. Why can't you use an iterator? — Ben N
– Ben N, Commented Nov 29, 2015 at 23:46
Your Friends will need to override (and correctly implement) the equals and hashcode methods. You should then be able to use ArrayList#remove(T) to remove and element by creating a new Friends object with the EXACT same properties as the one you have in you List — MadProgrammer
– MadProgrammer, Commented Nov 29, 2015 at 23:48
I might be off but how did case 2 even compile? You're trying to remove a String from an ArrayList of Friends. — Blazo
– Blazo, Commented Nov 29, 2015 at 23:55
Yeah, its a homework so we "haven't" yet seem iterators in java, is part of the specification of the homework... — Jsch
– Jsch, Commented Nov 29, 2015 at 23:57
@Jsch Have you seen a loop? Because essentially ANY answer will use a form of iteration within it's own implementation — MadProgrammer
– MadProgrammer, Commented Nov 30, 2015 at 0:01

sprinter · Accepted Answer · 2015-11-30 01:45:09Z

3

A simple mechanism to use is removeIf. Something like:

friendsList.removeIf(friend -> friend.hasName(name);

Note this uses Java 8.

That is assuming a hasName method of Friend. If you only have getName then:

friendsList.removeIf(friend -> friend.getName().equals(name));

edited Nov 30, 2015 at 1:45

answered Nov 29, 2015 at 23:56

sprinter

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2 Comments

Jsch Over a year ago

Yes, I'm very new in java. But how do you apply ("whatevernamehere") dynamically so the user is the one who selects which friend to remove. I don't quite understand well, thanks!

Jsch Over a year ago

I'll update my main post with my second class (constructor and methods)

JayC667 · Accepted Answer · 2015-11-29 23:59:41Z

Simple problem: instead of passing a Friends Object to the remove() method, you pass just the String. Write a custom remove code.

Also keep in mind to always do indexed deleting from bottom to top to not jump entries:

            System.out.print("Enter Friend's name to remove: ");
            name = input.next();

            //                  friendsList.remove(name);
            System.out.println("Trying to locate <" + name + ">");
            for (int i = friendsList.size() - 1; i >= 0; --i) {
                final Friends f = friendsList.get(i);
                System.out.println("\tChecking with <" + friendsList.get(i).name + ">");
                if (f.name.equals(name)) {
                    System.out.println("Found that bitch at index " + i);
                    friendsList.remove(i);
                    System.out.println("... and kicked him out");
                }
            }

            break;

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