How to create a Java object from a string representation at runtime

Question

Eg if I have a string "{1,2,3,4,5}" I would like to get an int[] object from that string.

I have looked a bit at Janino and Beanshell, but can't seem to find the correct way to get them to do this for me.

I am looking for a generic solution, one that works for all types - not only integer arrays.

Just a normal Java string containing something like "{1,2,3}", "1", "Stackoverflow" and so forth. — Mellson
– Mellson, Commented Jun 18, 2012 at 10:37
That's a different question, since now you're asking about converting an essentially arbitrary string into, apparently, arbitrary Java objects. What are you really trying to do? — Dave Newton
– Dave Newton, Commented Jun 18, 2012 at 10:38
I am trying to create objects based on what a user types in a field. So if a user types {1,2,3}, I want an int array. If the user types Hello, I want a string. — Mellson
– Mellson, Commented Jun 18, 2012 at 10:44
ok, do not go this way... it's a lot of parsing... there is no clean way to do so... you never know, what the user is typing into your textfiel — headgrowe
– headgrowe, Commented Jun 18, 2012 at 10:45

amicngh · Accepted Answer · 2012-06-18 10:52:16Z

2

Better to use Regular Expression.Not necessary that your String is Array it could be any String which contains numbers.

        String s="{1,2,3,4,5}";
        Pattern p = Pattern.compile("-?\\d+");
        Matcher m = p.matcher(s);
        List<Integer> list=new ArrayList<Integer>();
        while (m.find()) {
          Integer num=new Integer(m.group());

          list.add(num);
        }

        System.out.println(list);

Output:

[1, 2, 3, 4, 5]

answered Jun 18, 2012 at 10:52

amicngh

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1 Comment

amicngh Over a year ago

That's true , but he asking generic way so here it is

headgrowe · Accepted Answer · 2012-06-18 10:38:46Z

2

looks like a parse problem to me. look at the string methods :)

the code could look like:

String s = "{1,2,3,4,5}"
String justIntegers = s.substring(1, s.length()-1);
LinkedList<Integer> l = new LinkedList();
for (String string: justIntegers.split(','))
l.add(Integer.valuesOf(string));
l.toArray();

if you are using strings to send/save objects pls use xml or json...

answered Jun 18, 2012 at 10:38

headgrowe

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4 Comments

Mellson Over a year ago

Thanks for the effort, that would work if all I am getting is integer arrays. However I would like a generic solution.

headgrowe Over a year ago

for a generic solution, use "XStream" it's a java-lib to convert java objects to xml-strings and back... just 1 line code each... really usefull

Mellson Over a year ago

Thanks, I will try that straight away

headgrowe Over a year ago

you can just read/convert xml-Strings... not normal strings... its a way to send/save java-objects via String or byte[]

Community · Accepted Answer · 2017-05-23 10:34:26Z

2

Take a look at https://stackoverflow.com/a/2605050/1458047

The answer proposes a few options.

edited May 23, 2017 at 10:34

CommunityBot

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answered Jun 18, 2012 at 10:46

Christoph Eberhardt

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