在文件中查找一个单词，将其存储在数组列表中，并确保该单词不会被多次占用？

Question

public ArrayList<String> getWords()
{
    int size1 = lines.size();
    int size2 = 0;
    int counter3 = 0;
    ArrayList<Integer> checkthewords;
    for (int x = 0; x < size1; x++)
    {
        size2 = lines.get(x).substring(x).length();
        for (int y = 0; y < size2; y++)
        {
            if (Character.isLetter(charAt(((lines.get(x)).indexOf(x, z + x)))))
            {
                words.set(z, lines.get(x).substring(x,z + 1));
            }
            else
            {
                checkthewords.set(counter3, words);
                counter3++;
            }
            if (checkthewords.get(x).equals(checkthewords.get(counter3)))
            {

            }
        }
    }
    return words;
}

The method above is a called getWords(). I am trying to get a word from a file and store it in the arrayList checkthewords. I want to make sure that a word is not going to be stored in the arrayList checkthewords more than once.

I have the if statement:

            if (Character.isLetter(charAt(((lines.get(x)).indexOf(x, z + x)))))

But, don't know where to go from there.

Answer 1

You should use Set in Java to store elements when duplicates are not allowed.

A collection that contains no duplicate elements.

If you want to retain insertion order as well then use LinkedHashSet which is Hash table and linked list implementation of the Set interface, with predictable iteration order.

Kindly refer to below tutorials to understand application of Set in java.
Tutorial 1
Tutorial 2
Tutorial 3

See Also-:
HashSet vs TreeSet vs LinkedHashSet
HashSet vs LinkedHashSet

Answer 2

I'm pretty sure your code won't run at the moment. You are doing some strange things in there and I don't really understand it.

Try to approach this one step at a time.

The first step is to get the word from the file. Make sure you can parse the line and extract the word you want.

Then you need to check if the word exists in your checkthewords list. If it doesn't exist, add it. You can use the contains method provided by List to see if the list contains something.

if(!checkthewords.contains(word)) {
    // it's not in the list yet, add it
    checkthewords.add(word);
}

Also when you create your checkthewords list, you don't initialise it (so it's null):

ArrayList<String> checkthewords;

should be:

ArrayList<String> checkthewords = new ArrayList<String>();

And you shouldn't use checkthewords.set() like that. set is used to replace an existing element, not to add a new element. You could easily be setting an element that doesn't exist yet and throw an ArrayIndexOutOfBoundsException . Use checkthewords.add(word) to add something to your list.

See the ArrayList documentation .

set(int index, E element)

Replaces the element at the specified position in this list with the specified element.

It seems like you're overthinking this. Keep it simple. :)