How To Return An ArrayList Of Objects

Question

I have an ArrayList in a class called Room that contains the Character object. I want to be able to print off a description that will give a list of the Characters in a Room. I have made a toString method in the character class that will return the names of the characters but cant get it to work from the Room class. Im fairly new to programming and still getting use to arrays, any help would be appreciated!

Here is the addCharacter method that adds a character to the Room arraylist.

 public void addCharacter(Character c)
{
    assert c != null : "Room.addCharacter has null character";
    charInRoom++;
    charList.add(c); 
    System.out.println(charList);

    // TO DO
}

Here is the getLongDescription() class that I to use to print the list of characters in the room. (This is the method im having trouble with).

public String getLongDescription()
{
    return "You are " + description + ".\n" + getExitString() 
    + "\n" + charList[].Character.toString;  // TO EXTEND
}

And here is the toString method in the Character class. This method works.

public String toString()
{
    //If not null (the character has an item), character 
    //and item description will be printed.
    if(charItem != null){
        return charDescription +" having the item " + charItem.toString();
    }
    //Otherwise just print character description.
    else {
        return charDescription;
    }

}

What exactly is your question? Can you provide code from the "Room class" where you seem to be invoking the method? — Ivan Kukic
– Ivan Kukic, Commented Feb 19, 2019 at 20:31
Possible duplicate of How do I create a toString method for an ArrayList of objects? — Jeppe
– Jeppe, Commented Feb 19, 2019 at 20:33

LppEdd · Accepted Answer · 2019-02-19 20:33:35Z

1

As you're using a List<Character>, and you already implemented your custom toString method, you can just call characters.toString().

public String getLongDescription() {
    return "You are " + description + ".\n" + getExitString() 
    + "\n" + characters; // toString implicitly called.
}

The ArrayList#toString method will simply call each element's toString.

public String toString() {
    Iterator<E> it = iterator();
    if (! it.hasNext())
        return "[]";
    StringBuilder sb = new StringBuilder();
    sb.append('[');
    for (;;) {
        E e = it.next();                                 // Get the element
        sb.append(e == this ? "(this Collection)" : e);  // Implicit call to toString
        if (! it.hasNext())
            return sb.append(']').toString();
        sb.append(',').append(' ');
    }
}

answered Feb 19, 2019 at 20:33

LppEdd

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5 Comments

David Conrad Over a year ago

I'm not sure including all the code of ArrayList's toString method here is going to be helpful to a beginner. It might create more confusion. Of course, I could be wrong.

LppEdd Over a year ago

@DavidConrad you're right David. I added a couple of comments near the "important" lines. Anyway, if he/she has questions, I'm here to answer them.

ol1ie310 Over a year ago

Is there possibly a way to do it by not changing the toString function as this is an assignment and i cannot change this function.

LppEdd Over a year ago

@ol1ie310 which toString? Of which class?

LppEdd Over a year ago

@ol1ie310 if you mean the method I posted above, it's a standard method from ArrayList. You don't have to write or edit anything.

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