Is there a direct equivalent in Java for Python's str.join?
Question:
Possible Duplicates:
What’s the best way to build a string of delimited items in Java?
Java: convert List<String> to a join()d string
In Java, given a collection, getting the iterator and doing a separate case for the first (or last) element and the rest to get a comma separated string seems quite dull, is there something like str.join in Python?
Extra clarification for avoiding it being closed as duplicate: I’d rather not use external libraries like Apache Commons.
Thanks!
update a few years after…
Answers:
There is nothing in the standard library, but Guava for example has Joiner that does this.
Joiner joiner = Joiner.on(";").skipNulls();
. . .
return joiner.join("Harry", null, "Ron", "Hermione");
// returns "Harry; Ron; Hermione"
You can always write your own using a StringBuilder, though.
For a long time Java offered no such method. Like many others I did my versions of such join for array of strings and collections (iterators).
But Java 8 added String.join():
String[] arr = { "ala", "ma", "kota" };
String joined = String.join(" ", arr);
System.out.println(joined);
A compromise solution between not writing extra “utils” code and not using external libraries that I’ve found is the following two-liner:
/* collection is an object that formats to something like "[1, 2, 3...]"
(as the case of ArrayList, Set, etc.)
That is part of the contract of the Collection interface.
*/
String res = collection.toString();
res = res.substring(1, res.length()-1);
Nope there is not. Here is my attempt:
/**
* Join a collection of strings and add commas as delimiters.
* @require words.size() > 0 && words != null
*/
public static String concatWithCommas(Collection<String> words) {
StringBuilder wordList = new StringBuilder();
for (String word : words) {
wordList.append(word + ",");
}
return new String(wordList.deleteCharAt(wordList.length() - 1));
}
Not in the standard library. It is in StringUtils of commons lang.
Possible Duplicates:
What’s the best way to build a string of delimited items in Java?
Java: convert List<String> to a join()d string
In Java, given a collection, getting the iterator and doing a separate case for the first (or last) element and the rest to get a comma separated string seems quite dull, is there something like str.join in Python?
Extra clarification for avoiding it being closed as duplicate: I’d rather not use external libraries like Apache Commons.
Thanks!
update a few years after…
There is nothing in the standard library, but Guava for example has Joiner that does this.
Joiner joiner = Joiner.on(";").skipNulls(); . . . return joiner.join("Harry", null, "Ron", "Hermione"); // returns "Harry; Ron; Hermione"
You can always write your own using a StringBuilder, though.
For a long time Java offered no such method. Like many others I did my versions of such join for array of strings and collections (iterators).
But Java 8 added String.join():
String[] arr = { "ala", "ma", "kota" };
String joined = String.join(" ", arr);
System.out.println(joined);
A compromise solution between not writing extra “utils” code and not using external libraries that I’ve found is the following two-liner:
/* collection is an object that formats to something like "[1, 2, 3...]"
(as the case of ArrayList, Set, etc.)
That is part of the contract of the Collection interface.
*/
String res = collection.toString();
res = res.substring(1, res.length()-1);
Nope there is not. Here is my attempt:
/**
* Join a collection of strings and add commas as delimiters.
* @require words.size() > 0 && words != null
*/
public static String concatWithCommas(Collection<String> words) {
StringBuilder wordList = new StringBuilder();
for (String word : words) {
wordList.append(word + ",");
}
return new String(wordList.deleteCharAt(wordList.length() - 1));
}
Not in the standard library. It is in StringUtils of commons lang.