問題添加到ArrayLists

Question

我看過視頻，搜索過該網站以及許多其他網站，但沒有任何幫助。 這是我第一次使用ArrayLists。 如果我將ArrayList作為String可以，但是一旦我設置Comment（這是該類），它就不再起作用。 但是導師暗示這就是它的用法。 我還有另外兩個需要訪問它的類，當然還有main方法。

我遇到的主要問題是它不允許我添加到arraylist。 而且我很困惑，這可能真的很簡單。

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

問題是您嘗試添加String但是數組列表中需要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

您可以修改代碼以執行以下操作：

/**
 *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));
}

要打印注釋，可以添加toString方法，如下所示：

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

這樣，System.out.println（comment）; 將打印：

ID : 123412, Comment : This is a comment

對於這樣實例化的對象：

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