Issues adding to ArrayLists

Question

I have watched videos, searched this websites and many others, but nothing really helps. This is the first time I have used ArrayLists. If I have the ArrayList as String it's fine, but as soon as I set Comment (which is the class) it no longer works. But the tutor has implied that this is how it's meant to be used. I have two other classes that need access to it plus obviously the main method.

Main problem I am having is it won't allow me to add to the arraylist. And I'm stumped and it's probably really simple.

public class Comment {

// somehow need to link it to the game/app
private ArrayList<Comment> Reply = new ArrayList<Comment>();

private String usrComment;
private String usrID;

public Comment() {
}

public Comment(String usrID, String usrComs) {
    this.usrComment = usrComs;
    this.usrID = usrID;
}

public void addReview(String addRev) {

    this.Reply.add(addRev); // not working
}

public void addReply(String addRep) {

    Reply.add(addRep); // not working and I cannot figure it out
}

public void printRep() {
    for (Comment comment : Reply) {
        System.out.println(comment);
    }
}

}

The method add(Comment) in the type ArrayList<Comment> is not applicable for the arguments (String — N Woods
– N Woods, Commented May 12, 2018 at 13:55
Well, it itsn't: you're giving it a string, your list expects Comments. — Dave Newton
– Dave Newton, Commented May 12, 2018 at 13:56
Well, read what the compiler must have told you. Your "not working" is in fact "not compilable" and just follow the compiler error message: you cannot assign String to Comment and vice versa. — Honza Zidek
– Honza Zidek, Commented May 12, 2018 at 13:58
This is where I show my ignorance. Isn't Comment just an object of the Comment class? — N Woods
– N Woods, Commented May 12, 2018 at 14:00

StaticBeagle · Accepted Answer · 2018-05-12 14:04:03Z

3

The problem is that you are trying to add a String but the array list is expecting a Comment

public void addReview(String addRev) {
    // Reply is an ArrayList<Comment> of Comments not of Strings
    // this.Reply.add(addRev); // not working
    // you can create a new Comment and then add that comment
    this.Reply.add(new Comment("userId", addRev));
}

public void addReply(String addRep) {
    // same here
    // Reply.add(addRep); // not working and I cannot figure it out
    // you can create a new Comment and then add that comment
    this.Reply.add(new Comment("userId", addRep));
}

edited May 12, 2018 at 14:04

answered May 12, 2018 at 13:59

StaticBeagle

5,2052 gold badges27 silver badges36 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

N Woods Over a year ago

Wow thanks, like I said it's probably really simple. I have a terrible tutor. A lovely person, but she cannot teach. If I had known that at the start I would have saved so much time.

StaticBeagle Over a year ago

@NWoods Glad I could help! To be honest, it threw me off a bit because in real life, "comments are strings" haha.

Aditya Satyavada · Accepted Answer · 2018-05-12 14:14:21Z

You could modify your code to do the following :

/**
 *id - ID of the user reviewing the comment
 *review - The review comment made by the user
 */
public void addReview(String id, String review) {
this.Reply.add(new Comment(id,review));
}

/**
 *id - ID of the user replying
 *review - The reply comment made by the user
 */
public void addReply(String id, String reply) {
this.Reply.add(new Comment(id,reply));
}

To print the comment, you could add a toString method as follows :

public String toString(){
  return "ID : "+this.usrID+", Comment : "+this.usrComment;
}

That way, System.out.println(comment); will print :

ID : 123412, Comment : This is a comment

for an object instantiated like this :

Comment comment = new Comment("123412", "This is a comment")

I did that and it worked, but the way the main method is setup it just would work.
@NWoods I've edited my answer so that you can improve your code slightly. I'd suggest putting this up on codereview.stackexchange.com

Collectives™ on Stack Overflow

Issues adding to ArrayLists

2 Answers 2

2 Comments

2 Comments

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

2 Comments

Related