Store indexes in an array

Question

I need help on how I can store the indexes of a particular word occurring in a sentence. I need to store the indexes in an array so that I can access it later. I'm using a while loop but its not working.

while (index > 0) {

            for (int i = 0; i < data.length; i++) {

                data[i] = index;

            }

            System.out.println("Index : " + index);


            index = input.indexOf(word, index + word.length());

        }

Can you add detail about what exactly you are trying to accomplish, what you want data to hold and what index is initialized to? — Stephen L, Apr 04 '11 at 20:16
@Stephen L: [here's the original question](http://stackoverflow.com/questions/5533164/of-times-a-single-word-in-a-sentence/5533329). — mre, Apr 04 '11 at 20:30

score 0 · Accepted Answer · answered Apr 04 '11 at 20:23

I've commented up your code below. Please read the comments for understanding.

while (index > 0) { //String.indexOf can return a 0 as a valid answer. Use -1.
//Looping over something... Why don't you show us the primer code?
    for (int i = 0; i < data.length; i++) {
        /*
        Looping over the `data` array.
        You're filling every value of `data` with whatever is in `index`. Every time.
        This is not what you want.
        */      
        data[i] = index; 
    }

    System.out.println("Index : " + index);
    //OK
    index = input.indexOf(word, index + word.length());
}

Replace your data array and associated loop with an ArrayList. Use ArrayList.add() for every index you find.

score 0 · Answer 2 · edited May 23 '17 at 11:46

0

If you are trying generate a list of the indices of a word in a string, try using the indexOf(String str, int fromIndex) overload (from the Java API).

EDIT : Also check out this question: Stack Overflow: Java Counting # of occurrences of a word in a string

edited May 23 '17 at 11:46

Community

1
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answered Apr 04 '11 at 20:24

user664939

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score 0 · Answer 3 · answered Apr 06 '11 at 23:19

If you are asking about a structure type you would use then I would suggest to go with a Map of Strings (names of words) to List of Integers (indexes of these words).

The class below shows how I implemented a Map storing Lists.



import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Set;

/**
 * Class of a map which allows to have a list of items under a single key. 
 * @author Konrad Borowiecki
 *
 * @param <T1> type of the key.
 * @param <T2> type of objects the value list will store.
 */
public class ListHashMap<T1, T2> extends HashMap<T1, List<T2>>
{
    private static final long serialVersionUID = -3157711948165169766L;

    public ListHashMap()
    {
    }

    public void addItem(T1 key, T2 item)
    {
        if(containsKey(key))
        {
            List<T2> tml = get(key);
            tml.add(item);
        }
        else
        {
            List<T2> items = new ArrayList<T2>();
            items.add(item);
            put(key, items);
        }
    }

    public void removeItem(T1 key, T2 item)
    {
        List<T2> items = get(key);
        items.remove(item);
    }

    public void removeItem(T2 item)
    {
        Set<java.util.Map.Entry<T1, List<T2>>> set = entrySet();
        Iterator<java.util.Map.Entry<T1, List<T2>>> it = set.iterator();

        while(it.hasNext())
        {
            java.util.Map.Entry<T1, List<T2>> me = it.next();
            if(me.getValue().contains(item))
            {
                me.getValue().remove(item);
                if(me.getValue().isEmpty())
                    it.remove();
                break;
            }
        }
    }
}

In your case you would have a mapping of words to list of indexes so, you would call the class like this: ListHashMap<String,Integer> wordToIndexesMap = new ListHashMap<String,Integer>();

Enjoy, Boro.

Store indexes in an array

3 Answers3