Add(concatenate) to elements of Arraylist from another arraylist

Question

, I'm comparing one arrayList with another arrayList, if elements that are "contained" in both i would like to attach the element in the second arraylist to the element in the first along with "== neg==". The problem is I'm creating a new element in the first Arraylist instead of appending it to the element. I'm new to programming any assistance would be appreciated!!

 public static List<String> neg_compare(  List<String>tagged, List<String>negative_words, List<String>total_compare )
        {
        //int pos_sentiment = 0;
        //int pos_count = 0;
        int total_tweets = 0;
        int neg_count = 0;


                for(int j =0 ; j < tagged.size(); j++)
                {
                    total_tweets ++;
                    total_compare.add(tagged.get(j));

                    for(int  k = 0; k < negative_words.size(); k++)
                    {
                        if(tagged.get(j).contains(negative_words.get(k)))
                        {

                            //pos_count ++;

                            total_compare.add( "   == neg == " + negative_words.get(k) +"\n");

                        }
                    }
                    System.out.print(total_compare + "\n");
                    System.out.print(total_tweets);
                }
                    return total_compare;
            }
}

Please put more effort into formatting your code before you post - it's all over the place at the moment. Look at the preview when you're writing your post, and only submit the post when it looks reasonable. It would also help massively if you'd give a short but complete program which demonstrates the problem. (Say what you expected to happen vs what actually happened.) — Jon Skeet
– Jon Skeet, Commented Mar 11, 2014 at 9:14
You are not allowed to make changes to an arraylist inside of normal loops. To be able to add, remove or modify an ecisting element you should be using an Iterator. Information on how to use them in your example can be found at the Java Tutorial Docs: docs.oracle.com/javase/tutorial/collections/interfaces/… I hope this information can help. — Remy Baratte
– Remy Baratte, Commented Mar 11, 2014 at 9:16
You said that " I'm creating a new element in the first Arraylist instead of appending it to the element" - this sounds as if it might be worth mentioning that you can not modify strings. (But maybe I misunderstood something here - your intention is not very clear) — Marco13
– Marco13, Commented Mar 11, 2014 at 9:24
@Marco13: That is the way I know it, however, I did a quick test and I did not get any exceptions. I am not sure if it is because I am not messing around with the order or the size of the list though... — npinti
– npinti, Commented Mar 11, 2014 at 9:26

npinti · Accepted Answer · 2014-03-11 09:17:47Z

1

You should take a look at the .set(int index, E element) method. This would allow you to replace an old element with a new one, so in your case, you could have something like so: total_compare.set(j, total_compare.get(j) + " == neg == " + negative_words.get(k) +"\n");

answered Mar 11, 2014 at 9:17

npinti

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user3359502 · Accepted Answer · 2014-03-12 19:36:11Z

    public static List<String> pos_compare(List<String> pos_words, List<String>sentiment,List<String>positive_tweets , List<String>negative_words )
    {

    int pos_count = 0;
    int total_tweets = 0;



            for(int j =0 ; j < sentiment.size(); j++)
            {
                total_tweets ++;

                //Search each tweet with words from pos.word
                for(int  k = 0; k < pos_words.size(); k++)
                {
                    if(sentiment.get(j).contains(pos_words.get(k)))
                    {

                        pos_count ++;

                    }

                }
                //Search for negative
                for(int i  = 0 ; i< negative_words.size() ; i++)
                {
                    if(sentiment.get(j).contains(negative_words.get(i)))
                    {

                        pos_count --;

                    }
                }
                if ((pos_count) > 0)
                {
                    positive_tweets.add(sentiment.get(j) + "positive" + "\n" );
                }
                else if((pos_count) == 0)
                {
                    positive_tweets.add( sentiment.get(j) +  "neutral" +"\n");
                }
                else if((pos_count) < 0)
                {
                    positive_tweets.add( sentiment.get(j) + "negative" + "\n");
                }


                pos_count = 0;
            }
            //System.out.print(positive_tweets + "\n");
            return positive_tweets;
    }

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