Print array of sentences vertically

Question

Suppose I have an array of sentences:

[ "How To Format", "put returns between paragraphs", "for linebreak add 2 spaces at end" ]

I want to print it like this:

How        put            for
To         returns        linebreak
Format     between        add
           paragraphs     2
                          spaces
                          at
                          end

Here's my code:

public static void solve(String[] sentences) {
    int n = sentences.length;

    if(n == 0)
        return;

    List<List<String>> matrix = new ArrayList<List<String>>();
    int maxLength = Integer.MIN_VALUE;

    for(String sentence : sentences) {
        List<String> words = Arrays.asList(sentence.split(" "));
        maxLength = Math.max(maxLength, words.size());

        matrix.add(words);
    }

    for(int col = 0; col < maxLength; col++) {
        for(int row = 0; row < matrix.size(); row++) {
            try {
                System.out.format("%-15s", matrix.get(row).get(col));
            }
            catch(IndexOutOfBoundsException e) {
                System.out.format("%-15s", "");
            }
        }
        System.out.println();
    }
}

Is this easy to understand? Can I make it simpler, such as by using different data structures?

Answer 1

Use if statements rather than try/catch

Your method is understandable, you shouldn't use try catch, instead simply check that the index does not exceed the length. e.g.

if (col < matrix.get(row).size()) {
   // print what you want
} else {
   // print just a space
}

Better Regex

Rather than sentence.split(" "); The regex you want is sentence.split("\\s+) This ensures that you get all spaces and don't have an incorrect array length due to splitting on multiple empty spaces in a row. You can read more on Regex here.

Though this only applies if you don't want spaces to delimit words, ever, which is the assumption. The input itself sounds like it has to do with the specifications of the problem, but I simply took it as input and nothing more.

Use two dimensional arrays

You also don't need the list overhead for this. Simply use a two dimensional of the same size as the original array and make the inner arrays the result of calling the aforementioned split() method.

public static String[][] convertToWordArray(String[] input) {
        String[][] result = new String[input.length][];

        for (int i = 0; i < result.length; i++) {
            result[i] = input[i].trim().split("\\s+");
        }

        return result;
}

Alternative Implmentation:

public class Format {
    public static void main(String[] args) {
        String[] target = {
            "How To Format",
            "put returns between paragraphs",
            "for linebreak add 2 spaces at end"
        };

        printWordsVertically(target);
    }
/* These next two methods are relics of my initial implementation
   You can adjust for the use of 2d arrays and only need 1 method. */
    public static int wordCount(String input) {
        return input.trim().split("\\s+").length;
    }

    public static int longestWordCount(String[] input) {
        int result = 0;

        for (String s : input) {
            if (result < wordCount(s)) {
                result = wordCount(s);
            }
        }

        return result;
    }

    public static void printWordsVertically(String[] input) {
        int longestWordCount = longestWordCount(input);
        int spacesBetweenColumns = 7; // use needed int, or pass as argument
        String formatSpecifier = "%-" + (longestWordCount + spacesBetweenColumns) + "s";
        String[][] words = convertToWordArray(input);

        for (int i = 0; i < longestWordCount; i++) {
            for (int j = 0; j < words.length; j++) {
                if (i < words[j].length) {
                    System.out.printf(formatSpecifier, words[j][i]);
                } else {
                    System.out.printf(formatSpecifier, "");
                }
            }
            System.out.println();
        }
    }

    public static String[][] convertToWordArray(String[] input) {
        String[][] result = new String[input.length][];

        for (int i = 0; i < result.length; i++) {
            result[i] = input[i].trim().split("\\s+");
        }

        return result;
    }
}