Why do my array.size() give wrong value?

Question

I have an instance of ArrayList named array. When I parse some JSON data it will store it all in array. When I do a System.out.println(array); it will list a long list of items, around 30, but when I write System.out.println(array.size); it will give the value one.

How come it only gives me the value 1 when the list contains at least 30 values?

My code for this:

public void setLocationName (String name) {
 array = new ArrayList<String>();
 array.add(name);
 System.out.println(array); //This return a long list
 System.out.println(array.size()); //But this only return the value 1
}
public String[] getLocationName() {
 String tArray[] = null;
 for (int i = 0; i < array.size(); i++){
 System.out.println(i);
 tArray = array.toArray(new String[i]); 
 } 
 return tArray;
}

}

The long list :

[Brunnsparken, Göteborg]
[Brunnsgatan, Göteborg]
[Brunnslyckan, Lerum]
[Brunnsbotorget, Göteborg]
[Brunnsnäs, Ulricehamn]
[Brunnshult, Mellerud]
[Brunnsdal, Skövde]
[Brunns skola, Ulricehamn]
[Brunnsgården, Kungälv]
[Brunns kyrka, Ulricehamn]
[Boråsparken, Borås]
[Stadsparken, Ulricehamn]
[Lysekilsparken, Lysekil]
[Mössebergsparken, Falköping]
[Dalaborgsparken, Vänersborg]
[Rösparken, Åmål]
[Lillhagsparken Norra, Göteborg]
[Lillhagsparken Södra, Göteborg]
[Sylte Ryrbäcksparken, Trollhättan]
[Skogstomtsparken, Borås]
[Svinesundsparken, Norge]
[Håjumsparken, Trollhättan]
[Eriksdalsparken, Bollebygd]
[Fridhemsparken, Lidköping]

My result will be that only one item from the list will be returned in the tArray but I wanna return the whole list.

How to solve this?

• Michael Berry: You're creating a new array and adding 1 element to it - therefore, it's always, at the point you're printing out the size, going to only have 1 element in it.
• Boris the Spider: What do you mean by This return a long list? You create a new ArrayList then add one item. There is no way it can contain a long list. Please post an example of name.
• Josef: When I printe System.out.println(array); it gived a long list I posted it above
• Boris the Spider: Please provide an example.
• dapperwaterbuffalo: What is the content of the string parsed to the setter?

Answer 1

Java doesn't understand Json and basically what you're doing is add a string to an array

this.array.add(name); ---> add one value to the array, therefore the size is just one

you may need to use a specific Json library to parse the data in to an java arraylist.

regards

• Josef: So I have to split the String
• ajcm: yes, but you might have to do it by hand. Welcome to world of java =)

Answer 2

Look like you need to parse the String into pairs.

Looks to me like a Map might be the most appropriate structure to store the data in - I presume the first part from the value is unique.

Regex is probably the best approach to parsing the data:

public static void main(String[] args) {
 final String data = "[Brunnsparken, Göteborg]\n"
 + "[Brunnsgatan, Göteborg]\n"
 + "[Brunnslyckan, Lerum]\n"
 + "[Brunnsbotorget, Göteborg]\n"
 + "[Brunnsnäs, Ulricehamn]\n"
 + "[Brunnshult, Mellerud]\n"
 + "[Brunnsdal, Skövde]\n"
 + "[Brunns skola, Ulricehamn]\n"
 + "[Brunnsgården, Kungälv]\n"
 + "[Brunns kyrka, Ulricehamn]\n"
 + "[Boråsparken, Borås]\n"
 + "[Stadsparken, Ulricehamn]\n"
 + "[Lysekilsparken, Lysekil]\n"
 + "[Mössebergsparken, Falköping]\n"
 + "[Dalaborgsparken, Vänersborg]\n"
 + "[Rösparken, Åmål]\n"
 + "[Lillhagsparken Norra, Göteborg]\n"
 + "[Lillhagsparken Södra, Göteborg]\n"
 + "[Sylte Ryrbäcksparken, Trollhättan]\n"
 + "[Skogstomtsparken, Borås]\n"
 + "[Svinesundsparken, Norge]\n"
 + "[Håjumsparken, Trollhättan]\n"
 + "[Eriksdalsparken, Bollebygd]\n"
 + "[Fridhemsparken, Lidköping]";
 final Pattern pattern = Pattern.compile("\\[([^,]++),\\s++([^\\]]++)\\]");
 final Matcher matcher = pattern.matcher(data);
 final Map<String, String> items = new TreeMap<>();
 while (matcher.find()) {
 items.put(matcher.group(1), matcher.group(2));
 }
 for (final Entry<String, String> entry : items.entrySet()) {
 System.out.println(entry);
 }
}

Output from this:

Boråsparken=Borås
Brunns kyrka=Ulricehamn
Brunns skola=Ulricehamn
Brunnsbotorget=Göteborg
Brunnsdal=Skövde
Brunnsgatan=Göteborg
Brunnsgården=Kungälv
Brunnshult=Mellerud
Brunnslyckan=Lerum
Brunnsnäs=Ulricehamn
Brunnsparken=Göteborg
Dalaborgsparken=Vänersborg
Eriksdalsparken=Bollebygd
Fridhemsparken=Lidköping
Håjumsparken=Trollhättan
Lillhagsparken Norra=Göteborg
Lillhagsparken Södra=Göteborg
Lysekilsparken=Lysekil
Mössebergsparken=Falköping
Rösparken=Åmål
Skogstomtsparken=Borås
Stadsparken=Ulricehamn
Svinesundsparken=Norge
Sylte Ryrbäcksparken=Trollhättan

You can the access the items by looping (as above) or by getting values from the Map by key. The TreeMap I have used will sort the data by key, you can also use a LinkedHashMap to store the data in insertion order.

You could also store the items in a List of tuple like structures.

Answer 3

public void setLocationName (String name) {
 array = new ArrayList<String>();
 array.add(name);
 System.out.println(array); //This return a long list
 System.out.println(array.size()); //But this only return the value 1
}

You are creating a new ArrayList each time you call this method:

array = new ArrayList<String>();

You could just remove the above line, however I suggest you rename the method as this is no longer a setter and you are in fact now adding to an existing list each time you call this method.

I suggest what you want to do is build your List before parsing to the setter, perhaps using a foreach loop (I'm not sure what kind of object you are working with) and simplify your setter (setLocationName) to accomodate.

So it would become:

public void setLocationName(ArrayList<String> names)
 {
 this.array = names;
 System.out.println(array); //This return a long list
 System.out.println(array.size()); //But this only return the value 1
 }

• Josef: Actually just moving the arrayList solved the whole problem :-) Now my combobox display all the items from my JSON. You solved it.
• dapperwaterbuffalo: Problem by doing that is that you no longer have a traditional setter as you are actually now contributing to an existing list each time you call this method. So perhaps you should rename the method to something else at least.
• M7Jacks: Perhaps you should give this person credit for solving your problem.