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]); 
 }
}

• Roland Illig: Are you sure that you want to use the inefficient String + String in your answer?
• dariosicily: @RolandIllig Hello, I decided to use it to simplify how the string is built without use of StringBuilder even loosing in performance, probably not the best choice considering OP already used `StringBuilder' in the proposed approach.