Compare and retrieve elements from ArrayList

Question

I'm trying to build a simple dictionary that compares a string to a word on the ArrayList and then returns a different value from the list. The ArrayList is laid out with the foreign word and then followed by the English equivalent so the idea is that I type in a word, use scanner to compare it to the array list and then return the index value +1 so if the word I type is 7th on the list, I want it to return the 8th word and print it out.

I've got the basic idea of inputting a string and comparing it, but I don't know how to return the following word from the ArrayList:

public void translateWords(){
        String nameSearch;
        nameSearch=input.nextLine();

        for (Phrase c:phrases) {
            if (c.getName().equals(nameSearch))  {
                System.out.println( c.advancedToString());      
                return;
            }
        }
        System.out.println("not on list");

I've tried playing about with the get method for the ArrayList but I'm unsure on how to use it so any feedback would be very appreciated here.

If you want to create a dictionary, why not use a [dictionary](http://docs.oracle.com/javase/6/docs/api/java/util/HashMap.html)? — tobias_k, Nov 11 '13 at 11:06
You could do the loop the old way (i.e. using a integer counter) and then calling phrases.get(i+1) — orique, Nov 11 '13 at 11:13

score 0 · Answer 1 · edited Nov 11 '13 at 11:12

0

Would something like this do the job for you? Not tested, just from my head:

public void translateWords(){
    String nameSearch;
    nameSearch=input.nextLine();

    if(c.indexof(nameSearch)){
        System.out.println(c.get(c.indexof(c.indexof(nameSearch)+1));
    } else {
        System.out.println("not on list");
    }
}

edited Nov 11 '13 at 11:12

answered Nov 11 '13 at 11:10

Bjørn Jostein Aurheim

82
6

`indexOf` won't work this way, since it is a list of Phrases, not of Strings. – tobias_k Nov 11 '13 at 11:20
Moreover, the code is pretty wrong... The line `c.get(c.indexof(c.indexof(nameSearch)+1)` will try to get the index of... an index? Also, parentheses do not match. Drop the second `indexOf(`. Still, `indexOf` is called unnecessarily often, and won't work in the first place (see previous comment). – tobias_k Nov 11 '13 at 11:35

user987339 · Accepted Answer · 2013-11-11T11:15:56.470

for-each is not appropriate in this case because you can not access successive elements, in your case translated words. So I suggest you to use Iterate

I suppose phrases is of type List<Phrase>

public void translateWords(){
        String nameSearch;
        nameSearch=input.nextLine();

        Iterator<Phrase> it = phrases.iterator();
        while(it.hasNext())
        {
           Phrase c = it.next();
           if (c.getName().equals(nameSearch))  {
                System.out.println( it.next().advancedToString());      
                return;
            }
        }

        System.out.println("not on list");
}

Thank you, this one works a treat. It does exactly what I want it to. — Lukasz Medza, Nov 11 '13 at 11:26

score 0 · Answer 3 · edited May 23 '17 at 12:29

Another way would be to use a dictionary, e.g., a Java HashMap. Without knowing how your Phrase class is implemented, this might look like this:

// create dictionary
Map<Phrase, Phrase> d = new HashMap<Phrase, Phrase>();
// add phrases
d.put(new Phrase("Guten Tag", "de"), new Phrase("Good morning", "en"));
// get translation
Phrase p = d.get(new Phrase(nameSearch, "de"));

(To make this work, Phrase.equals and Phrase.hashCode have to be implemented.)

This seems to be a better choice of data structure for your task. Using a HashMap, lookup times for items are O(1), as opposed to O(n) in your approach, which could be relevant if your dictionary contains thousands or millions of phrases, or if you have to do this very often. A possible downside is that the entries have to be really equal, e.g. you could not (easily) check for "similar" phrases or words.

Compare and retrieve elements from ArrayList

3 Answers3

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