How can I convert List<Integer> to String? E.g. If my List<Integer> contains numbers 1 2 and 3 how can it be converted to String = "1,2,3"? Every help will be appreciated.
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4Why the downvotes? It's a good question and neither @GermannArlington or orangegoat have answered it.Joe– Joe2012-11-02 15:58:00 +00:00Commented Nov 2, 2012 at 15:58
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1Probably because "the question does not show any research effort".JB Nizet– JB Nizet2012-11-02 15:59:53 +00:00Commented Nov 2, 2012 at 15:59
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5Still, it's a useful question and from the answer it's not obvious. I think it's quite obvious that if a user is asking a question like this they are very new to the language and therefore this is a reasonable question. If there are no duplicate questions (I did't check) then that's an even stronger case. IMHO.Joe– Joe2012-11-02 16:04:28 +00:00Commented Nov 2, 2012 at 16:04
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1I've tried to find solution but I could't find solution that solves my problem. I don't understand what is wrong with my question...Martin– Martin2012-11-02 16:08:28 +00:00Commented Nov 2, 2012 at 16:08
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4@Martin, Joe: when you ask such a question, don't just ask for a solution for your problem. Show what you have tried to solve the problem, and explain what you're having problems with. This is what consitutes a "Research effort". Otherwise, it just looks like: "Hey, I'm too lazy to find out how to do this simple thing. Could anyone do it for me?".JB Nizet– JB Nizet2012-11-02 16:11:46 +00:00Commented Nov 2, 2012 at 16:11
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5 Answers
In vanilla Java 8 (streams) you can do
// Given numberList is a List<Integer> of 1,2,3...
String numberString = numberList.stream().map(String::valueOf)
.collect(Collectors.joining(","));
// numberString here is "1,2,3"
1 Comment
Camille
Better, nicer, newer way to do it properly ++1!
I think you may use simply List.toString() as below:
List<Integer> intList = new ArrayList<Integer>();
intList.add(1);
intList.add(2);
intList.add(3);
String listString = intList.toString();
System.out.println(listString); //<- this prints [1, 2, 3]
If you don't want [] in the string, simply use the substring e.g.:
listString = listString.substring(1, listString.length()-1);
System.out.println(listString); //<- this prints 1, 2, 3
Please note: List.toString() uses AbstractCollection#toString method, which converts the list into String as above
2 Comments
ed22
The format of the string returned by AbstractCollection#toString is implementation specific I assume?
Ahmad Abdelghany
This is a bit hacky and outdated imo.
With Guava:
String s = Joiner.on(',').join(integerList);
2 Comments
One way would be:
Iterate over list, add each item to StringBuffer (or) StringBuilder and do toString() at end.
Example:
StringBuilder strbul = new StringBuilder();
Iterator<Integer> iter = list.iterator();
while(iter.hasNext())
{
strbul.append(iter.next());
if(iter.hasNext()){
strbul.append(",");
}
}
strbul.toString();
2 Comments
Aravind Yarram
StringBuilder if using Java 5 or greater
Bienvenido David
list.stream().map(String::valueOf).collect(Collectors.joining(",")) since Java 8.
Just to add another (of many) options from a popular library (Apache Commons):
import org.apache.commons.lang3.StringUtils;
String joinedList = StringUtils.join(someList, ",");
See documentation: https://commons.apache.org/proper/commons-lang/apidocs/org/apache/commons/lang3/StringUtils.html#join-java.lang.Iterable-java.lang.String-
An elegant option from others' comments (as of Java 8):
String joinedList = someList.stream().map(String::valueOf).collect(Collectors.joining(","));
