How to remove an object from a linked list in java

Question

I have a linkedlist called seatList made up of Seat objects set up like so...

public class Seat {

    int row, col;
    char type;

    Seat(int row, int col, char type){
        this.row = row;
        this.col = col;
        this.type = type;
    }

    String printSeat(){
        return "(" + row + ", " + col + ", " + type + ")";
    }

}

When i try to remove the seats with the same properties by creating a new seat object and storing it in a seperate linked list called collections, they do not get removed from the Linked List.

LinkedList<Seat> collection = new LinkedList();

    for (int q : indexToRemove){
        collection.add(new Seat(seatList.get(q).row, seatList.get(q).col, seatList.get(q).type));
    }

    for (Seat s : collection){
        if (seatList.contains(s)){
            println("true");
            seatList.remove(s);
        }

    }

    if (orders.get(indexes.get(index)).seatList.isEmpty()){
        orders.remove((int)indexes.get(index));
    }

Reason it is different: linked question talks about altering the list you are iterating as stated by csm_dev

Answer 1

To remove object from list you have to use Iterator and call remove() on iterator an example :

    Iterator<Seat> collection = seatList.iterator();
    while (collection.hasNext()) 
    {
       Seat element = collection.next();

       //some condition on your object "element"

        collection.remove();
      }

and don't foget to define hashCode/equals methodes logic to compare your Seat objects

Answer 2

You have to use Iterator for this :

Scanner scr= new Scanner(System.in);
System.out.print("Enter Seat Row number to delete: ");
int row = scr.nextInt();

for (Iterator<Seat> iter = list.iterator(); iter.hasNext();) {

    Seat data = iter.next();

    if (data.getRow() == row) {
        iter.remove();
    }
}

You have to add setters and getters in your been class.

Answer 3

LinkedList & other list implementations uses equals() method to check if the object is present in the list. Since you don't have equals() method implemented, java will use the implementation provided by Object class, which is very crude & not work for you.

You need to implement equals() method & give jvm a way to see if 2 objects of seat are same.

Answer 4

If you really don't need to create new objects to add to collection list, you can add objects from seatList and second for in you code snippet will remove objects from that list.

for (int q : indexToRemove){
    collection.add(seatList.get(q));
}

When you check weather list contains object or not, object's equals() method is used and you should implement it accordingly along with hashCode() method to get desired result.