Add comma/and between string array in java

Question

i get an array of authors from json response and i have to display authors name in TextView(android) in proper format like =>Viraj, Chetan and George R. R. Martin my code work fine, but it's a mess....

public class SeprateAuthors {
public static void main(String[] args) {
    String[] authors0 = {"a", "b"};
    String[] authors1 = {"a", "b", "c"};
    String[] authors2 = {"a", "b", "c","d"};
    String[] authors3 = {"a", "b", "c","d","e","f"};
    
    System.out.println(displayAuthors(authors0));
    System.out.println(displayAuthors(authors1));
    System.out.println(displayAuthors(authors2));
    System.out.println(displayAuthors(authors3));        
}
public static String displayAuthors(String[] authors) {
    StringBuilder stringBuilder = new StringBuilder();
    String stringAuthors="";
    String prefixComma = ", ";
    String prefixAnd = " and ";
    if ((authors != null) && (authors.length > 0)) {
        
        for (int i = 0; i < authors.length; i++) {
            if (i < authors.length - 2) {
                stringBuilder.append(authors[i]).append(prefixComma);
            } else {
                stringBuilder.append(authors[i]).append(prefixAnd);
            }
        }
        //  Java Remove extra Characters("and ") from String
        stringAuthors = stringBuilder.substring(0, stringBuilder.length() - 4);
    }
    return stringAuthors;
}

}

Answer 1

Welcome to Code Review, I have some hints about your code, starting from your main method:

public static void main(String[] args) {
    String[] authors0 = {"a", "b"};
    String[] authors1 = {"a", "b", "c"};
    String[] authors2 = {"a", "b", "c","d"};
    String[] authors3 = {"a", "b", "c","d","e","f"};
    
    System.out.println(displayAuthors(authors0));
    System.out.println(displayAuthors(authors1));
    System.out.println(displayAuthors(authors2));
    System.out.println(displayAuthors(authors3));        
}

You have defined several arrays forcing the multiple print , you can obtain the same result defining an 2d array storing arrays of different dimensions like below :

public static void main(String[] args) {
    String[][] authors = { {"a"},
                           {"a", "b"},
                           {"a", "b", "c"},
                           {"a", "b", "c","d"},
                           {"a", "b", "c","d","e","f"}};
    
    for (String[] row : authors) {
        System.out.println(displayAuthors(row));
    } 
}

About the print of the authors array you can distinguish three cases :

1. array with zero elements : you will print the "" empty string.
2. array with one element : you will print the unique element of the array.
3. array with more than one element : you will print elements with ", " as separator except for the penultimate element and the last one that will be separated by "and".

You can rewrite your displayAuthors method in this way:

public static String displayAuthors(String[] authors) {
    if (authors == null) { return ""; }
        
    switch (authors.length) {
        case 0: return "";
        case 1: return authors[0];
        default: return helperDisplayAuthors(authors);
    }
}

I defined a new method called helperDisplayAuthors :

private static String helperDisplayAuthors(String[] authors) {
    final int length = authors.length;
    String result = "";
        
    for (int i = 0; i < length - 2; ++i) {
        result += authors[i] + ", ";
    }
        
    return String.format("%s%s and %s", result, 
            authors[length - 2], authors[length - 1]);
    }

}

The method String.format helps you to compose the final string. Here the code of your class:

public class SeparateAuthors {

    public static void main(String[] args) {

        String[][] authors = {{"a"},
                              {"a", "b"},
                              {"a", "b", "c"},
                              {"a", "b", "c", "d"},
                              {"a", "b", "c", "d", "e", "f"}};

        for (String[] row : authors) {
            System.out.println(displayAuthors(row));
        }
    }
    
    public static String displayAuthors(String[] authors) {
        if (authors == null) { return ""; }
        
        switch (authors.length) {
            case 0: return "";
            case 1: return authors[0];
            default: return helperDisplayAuthors(authors);
        }
    }

    private static String helperDisplayAuthors(String[] authors) {
        final int length = authors.length;
        String result = "";
        
        for (int i = 0; i < length - 2; ++i) {
            result += authors[i] + ", ";
        }
        
        return String.format("%s%s and %s", result, 
                authors[length - 2], authors[length - 1]);       
    }

}