问题添加到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);
    }
}

}

Answer 1

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));
}

Answer 2

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")