Make ArrayList with words that start with specific letter?

Question

I am trying to make a method that takes in an ArrayList and a letter. If the words in the arraylist start with that letter, than it will be put into a new array of words that start with that letter. For example, an arraylist with ("Apple", "Anny", "Bob") and a letter of "A" would create a new arraylist ("Apple", "Anny"). I am not allowed to use .startsWith(char ch)

public ArrayList<String> wordsThatStartWith(ArrayList<String> words, String letter)
{
    ArrayList<String> newWords = new ArrayList<String>();
    for(int i = 0; i < words.size(); i++){
        if((words.get(i)).substring(i, i + 1) == letter){
        newWords.add(words.get(i));
    }
}
return newWords;
}

I am not sure why it will not add into a new ArrayList.

Use `words.get(i).charAt(0) == letter`. Also change `letter` to `char` instead of `String`. — cegredev, Apr 20 '20 at 21:33
I'd recommend you to read more about `String` class and it's methods. — the_tech_maddy, Apr 20 '20 at 21:36
@Schred I have to solve this problem without changing the parameters of the method — JohnCooket123, Apr 20 '20 at 21:36
`letter` is of type `String`, you compare it with `==`, and this won't work. — Johannes Kuhn, Apr 20 '20 at 21:37
Then take a look at the link Johannes Kuhn provided and change `substring(i, i + 1)` to `substring(0, 1)`. — cegredev, Apr 20 '20 at 21:38

Arvind Kumar Avinash · Accepted Answer · 2020-04-20T21:44:10.207

0

Replace

if((words.get(i)).substring(i, i + 1) == letter)

with

if((words.get(i)).substring(0, 1).equalsIgnoreCase(letter))

as you need to get just the first character from the string.

Using the enhanced for loop, you can write it as

for(String word: words) {
    if(word.substring(0, 1).equalsIgnoreCase(letter)){
        newWords.add(word);
    }   
}

edited Apr 20 '20 at 21:44

answered Apr 20 '20 at 21:40

Arvind Kumar Avinash

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Have you thought about using [`String.startsWith()`](https://docs.oracle.com/en/java/javase/14/docs/api/java.base/java/lang/String.html#startsWith%28java.lang.String%29)? – Johannes Kuhn Apr 20 '20 at 21:42
1

@JohannesKuhn Op is not allowed to use that. – cegredev Apr 20 '20 at 21:43
Then use `startsWith(String)`. It's an different method. Or `regionMatches`. – Johannes Kuhn Apr 20 '20 at 21:43
@JohannesKuhn - OP has mentioned, `I am not allowed to use .startsWith(char ch)`. By the way, what is wrong with my answer? – Arvind Kumar Avinash Apr 20 '20 at 21:46
Then use `startsWith(String)`. It's an different method. Or `regionMatches`. – Johannes Kuhn Apr 20 '20 at 21:48
@JohannesKuhn - Why should I use `use startsWith(String)`? You haven't answered if there is anything wrong with my answer. – Arvind Kumar Avinash Apr 20 '20 at 21:49
What about `regionMatches(true, 0, letter, 0, 1)`? You haven't answered why you did not consider this. – Johannes Kuhn Apr 20 '20 at 21:50
1

@JohannesKuhn I don't think that's a reason to downvote an answer. This one works fine and is in keeping with what OP tried. – cegredev Apr 20 '20 at 21:54
Last time I checked, "because I feel like it" was on the list of valid reasons. Anyway, not my downvote. – Johannes Kuhn Apr 20 '20 at 21:57

Make ArrayList with words that start with specific letter?

1 Answers1