Java: string split by regexp to get only integers

Your code is doing exactly what you tell it: split the string using "," as a delimiter:

"[1, 2, 3]" => "[1" , " 2", " 3]"

You could massage the string into shape before using split() - to remove the spaces and the square brackets. However a more direct, regex way to do it is to use a Matcher to scan through the input string:

    Pattern pattern = Pattern.compile("(\\d+)\\D+");
    ArrayList<String> list = new ArrayList<String>();
    Matcher matcher = pattern.matcher(input);
    while(matcher.find()) {
        list.add(matcher.group(1));
    }
    // if you really need an array
    String[] array = list.toArray(new String[0]);

This pattern (\d+)\D+ matches one or more digits, followed by one or more non-digits, and it captures the digits in a group, which you can access using matcher.group(1). It matches your input quite loosely; you could make it more specific (so that it would reject input in other forms) if you preferred.

Actually split function returns an array of string,That's why you getting this [].

Use replace method to do this.

Try this:

String str = "[1, 2, 3, 4]";
String num = str.replaceAll( "[^\\d,]", "" );

you will get String 1,2,3,4

Then use String[] allNums = num.split(",");

EDIT: this will also work for the input String str = "[[1], [2], [3], [4]]";

The regex that you give to the split method is used to determine the index of each split.

The cleanest solution to handle your case would be using Pattern.compile to create a pattern like [0-9]+ and then use the matcher to find each match in your source string.

Code example:

Pattern pattern = Pattern.compile("[0-9]+");
Matcher matcher = pattern.matcher(yourString);

while(matcher.find()) {
    System.out.println(matcher.group());
}

This prints out each consecutive number in yourString.

Appendix: if you use this piece of code often, create a static variable which compiles the Pattern already when loading the class, as pattern compilation is expensive. Like: private static final Pattern NUMBER_PATTERN = Pattern.compile("[0-9]+");

String s=s.substring(1,s.length()-1);
String s1[]=s.split(",");

this will give you the expected string.

Try doing this to the code:

yourString = yourString.replace ( /[^\d.]/g, '' );

replace the brackets [ ]and then split

str.replaceAll("\\[", "").replaceAll("\\]", "").split(",");