Question

I am trying to create a String[] which contains only words that comprise of certain characters. For example I have a dictionary containing a number of words like so:

arm
army
art
as
at
attack
attempt
attention
attraction
authority
automatic
awake
baby
back
bad
bag
balance

I want to narrow the list down so that it only contains words with the characters a, b and g. Therefore the list should only contain the word ‘bag’ in this example.
Currently I am trying to do this using regexes but having never used them before I can’t seem to get it to work.
Here is my code:

public class LetterJugglingMain {
public static void main(String[] args) {
    String dictFile = "/Users/simonrhillary/Desktop/Dictionary(3).txt";
    fileReader fr = new fileReader();
    fr.openFile(dictFile);
    String[] dictionary = fr.fileToArray();
    String regx = "able";
    String[] newDict = createListOfValidWords(dictionary, regx);
    printArray(newDict);
}

public static String[] createListOfValidWords(String[] d, String regex){
    List<String> narrowed = new ArrayList<String>();
    for(int i = 0; i<d.length; i++){
        if(d[i].matches(regex)){
            narrowed.add(d[i]);
            System.out.println("added " + d[i]);
        }
    }
    String[] narrowArray = narrowed.toArray(new String[0]);
    return narrowArray;
}

however the array returned is always empty unless the String regex is the exact word! Any ideas? I can post more code if needed…I think I must be trying to initialise the regex wrong.
The narrowed down list must contain ONLY the characters from the regex.

Answer 1

The OP wants words that contain every character. Not just one of them.
And other characters are not a problem.

If this is the case, I think the simiplest way would be to loop through the entire string, character by character, and check to see if it contains all of the characters you want. Keep flags to check and see if every character has been found.

If this isn’t the case…. :

Try using the regex:

^[able]+$

Here’s what it does:

^ matches the beginning of the string and $ matches the end of the string. This makes sure that you’re not getting a partial match.

[able] matches the characters you want the string to consist of, in this case a, b, l, and e. + Makes sure that there are 1 or more of these characters in the string.

Note: This regex will match a string that contains these 4 letters. For example, it will match:

able, albe, aeble, aaaabbblllleeee

and will not match

qable, treatable, and abled.