[Solved] Java formatting a arraylist

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I tried to guess what exactly you’re trying to achieve. Assuming you’ve got an ArrayList containing Strings, the following code will probably do what you want to achieve (use the method updateList to change an ArrayList that looks like your first example into an ArrayList that looks like your second example):

import java.util.ArrayList;
import java.util.regex.Pattern;
import java.util.regex.Matcher;

public class Main
{
    public static void main(String[] args)
    {
        ArrayList<String> list = new ArrayList<String>();
        list.add("netl"); list.add("etnl"); list.add("ltc"); list.add("6.3"); list.add("6.3");
        list.add("maat"); list.add("lo"); list.add("CombiGym"); list.add("mr"); list.add("wisB");
        list.add("nat"); list.add("schk"); list.add("biol"); list.add("6.4"); list.add("6.4");
        list.add("wisD"); list.add("L&W"); list.add("9"); list.add("8.5"); list.add("reken");
        list.add("exp");
        log(list);
        log(updateList(list));
    }

    public static ArrayList<String> updateList(ArrayList<String> list)
    {
        ArrayList<String> ret = new ArrayList<String>();
        for (int i=0; i<list.size(); i++)
        {
            if (i == 0)
                ret.add(list.get(i));
            else
            {
                Pattern p = Pattern.compile("^[0-9]+(\\.[0-9]+)?$");
                Matcher m = p.matcher(list.get(i));
                if (m.find()) ret.set(ret.size()-1, ret.get(ret.size()-1) + " " + list.get(i));
                else ret.add(list.get(i));
            }
        }
        return ret;
    }

    public static void log(ArrayList<String> list)
    {
        String logstr = "[";
        for (int i=0; i<list.size(); i++)
        {
            if (i > 0) logstr += ", ";
            logstr += list.get(i);
        }
        logstr += "]";
        System.out.println(logstr);
    }
}

If I run the code above, I get the following output:

[netl, etnl, ltc, 6.3, 6.3, maat, lo, CombiGym, mr, wisB, nat, schk, biol, 6.4, 6.4, wisD, L&W, 9, 8.5, reken, exp]
[netl, etnl, ltc 6.3 6.3, maat, lo, CombiGym, mr, wisB, nat, schk, biol 6.4 6.4, wisD, L&W 9 8.5, reken, exp]

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solved Java formatting a arraylist