Convert string to List

Question

I have a string with comma separated value that I am getting direclty from database. Now I want to pass that entire string to another query but the datatype required is long and i want to use in clause to get this done.

str1 = [123,456,789];

Is there any direct way to do it instead of looping.

To my knowledge the only method is looping. I would store them in a LinkedList for O(N*M) where M is the length of each number (cost for converting string to long) and N is the number of elements — Vineet Kosaraju, Nov 13 '13 at 06:38
Can you show the queries you're attempted to run? What RDBMS is this? — Mureinik, Nov 13 '13 at 06:40
When you say "comma separated value", are you talking about `.csv` file format, or numbers written for human consumption with a convention of commas between every group of 3 digits? — Robin Green, Nov 13 '13 at 06:45
@user2986404 If you are asking about limit of characers with IN clause: Check here http://stackoverflow.com/questions/1869753/maximum-size-for-a-sql-server-query-in-clause-is-there-a-better-approach — Nitin Dandriyal, Nov 13 '13 at 07:37
or if you could use jdbctemplate: http://stackoverflow.com/questions/1327074/how-to-execute-in-sql-queries-with-springs-jdbctemplate-effectivly — Nitin Dandriyal, Nov 13 '13 at 07:39

score 12 · Answer 1 · answered Nov 18 '15 at 02:07

12

You can use the Lambda functions of Java 8 to achieve this without looping

    String string = "1, 2, 3, 4";
    List<Long> list = Arrays.asList(string.split(",")).stream().map(s -> Long.parseLong(s.trim())).collect(Collectors.toList());

answered Nov 18 '15 at 02:07

virag

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6
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1

A slightly improved version: Stream.of(input.split(",")).map(s -> Long.parseLong(s.trim())).collect(Collectors.toList()); – naren May 23 '18 at 07:35

score 9 · Answer 2 · edited Mar 06 '22 at 09:47

9

A little shorter than virag's answer, as it skips asList() and doesn't do a string trim.

List<Long> list = Arrays.stream(str.split(",")).map(s -> Long.parseLong(s.trim())).collect(Collectors.toList());

edited Mar 06 '22 at 09:47

Stephan

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answered May 10 '18 at 21:54

Bienvenido David

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score 6 · Accepted Answer · 2015-11-25T07:58:07.050

6

With guava:

List<Long> longs = Lists.newArrayList(Iterables.transform(Splitter.on(',').split("1,2,3"), new Function<String, Long>() {
    public Long apply(final String in) {
        return in == null ? null : Longs.tryParse(in);
    }
}));

EDIT:

With a List<String> (stringList) as input:

List<Long> longs = Lists.newArrayList(Lists.transform(stringList, new Function<String, Long>() {
    public Long apply(final String in) {
        return in == null ? null : Longs.tryParse(in);
    }
}));

edited Nov 25 '15 at 07:58

answered Nov 13 '13 at 06:40

Hi Robin, this is giving me numberFormatException when I am passing the string. Actaully its List that I changed to String from toString() method. Or is there a way I can directlt use thie List to change to List? – user2986404 Nov 13 '13 at 07:32

score 2 · Answer 4 · answered Nov 13 '13 at 06:41

I doubt that you can do this without looping. Here is a sample workaround:

String str = "[123,456,789]";


Pattern pattern = Pattern.compile("\\d+");
Matcher matcher = pattern.matcher(str);

List<Long> list = new ArrayList<Long>();

 while (matcher.find()) {
System.out.println(matcher.group());
list.add(Long.parseLong(matcher.group())); // Add the value to the list
}
System.out.println(list);

score 2 · Answer 5 · answered Nov 13 '13 at 06:58

2

Use StringTokenizer and add split tokens to a list with a while loop.

StringTokenizer st = new StringTokenizer("1,2,3", ",");
List<Long> list = new ArrayList<Long>();
while (st.hasMoreTokens()) 
{
     list.add(Long.valueOf(st.nextToken()));
}

answered Nov 13 '13 at 06:58

Vignesh

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Kamlesh Arya · Answer 6 · 2013-11-13T06:54:47.017

0

you can try below code to get long value from a string

if str1="123,456,789"

 Long x=Long.parseLong(str1.replace(",",""));

and,

if str1="[123,456,789]"

Long x=Long.parseLong(str1.replace(",|\\[|\\]",""));

edited Nov 13 '13 at 06:54

answered Nov 13 '13 at 06:39

Kamlesh Arya

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Yes, if it is used for the whole string, but not if it is used for a valid long. – Robin Green Nov 13 '13 at 06:42
2

@RobinGreen the question is about a string that contains `,` and not how to parse a long – Narendra Pathai Nov 13 '13 at 06:45

score 0 · Answer 7 · answered Nov 13 '13 at 06:43

0

Use String.replace assuming str1 contains "[123,123,123]"

str1 = str1.replace(",|\\[|\\]",""); //should replace commas and brackets with nothing;

then you should be able to do

Long myLong =  Long.parseLong(str1);

answered Nov 13 '13 at 06:43

thermite

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19

I am assuming the questioner means comma separated value in the sense of `.csv` file format, not in the sense of a number written for human consumption with commas between every 3 digits, but you could be right! – Robin Green Nov 13 '13 at 06:44

Convert string to List

7 Answers7