Java, How do i add values to Object array

Question

I need to add values to an array of objects dynamically and pass that array variable to a function.

If I add values manually it works fine.

Object[][] listData = {{"Cheese", "Pepperoni", "Black Olives"},{"Cheese",    
"Pepperoni", "Black Olives"}};

This is the function that needs to use listData .

TableModel tblModel = new DefaultTableModel(new String[]{"Date", "Action", "Amount"}, listData);

but how can I add values into listData from a for loop?

ArrayList<Map<String, Object>> sampleArray =   (ArrayList)myPremiumspaid.get("Data"); 
for(int x =0; x<sampleArray.size(); x++)
 {
    //sampleArray.get(x).get("YearMonth");
   //listData[][] = "";  stuck here
 }

Java arrays have a fixed length; what do you mean "add values ... dynamically"? — Elliott Frisch
– Elliott Frisch, Commented May 3, 2016 at 13:02
i want to pull certain values from the Map, then populate Object[][], please check my updated question — Yung A
– Yung A, Commented May 3, 2016 at 13:12

Shai Almog · Accepted Answer · 2016-05-04 04:42:15Z

4

Arrays are fixed sized, after creating the array Object, you can't update it's size/ enlarge it's size. So the purpose to be dynamic size or auto growing sized, you need to use List ie. ArrayList.

Object[][] listData = {{"Cheese", "Pepperoni", "Black Olives"},{"Cheese",    
"Pepperoni", "Black Olives"}};

Instead:

List<List<Object>> listData=new ArrayList<List<Object>>();
listData.add(Arrays.asList("Cheese", "Pepperoni", "Black Olives"));
listData.add(Arrays.asList("Cheese", "Pepperoni", "Black Olives"));

But this ArrayList needs to be passed into a function which is taking array, so, you could convert the ArrayList to array object.

TableModel tblModel = new DefaultTableModel(new String[]{"Date", "Action", "Amount"}, (Object[][]) listData.toArray());

but how can I add values into listData from a for loop? Now you could do it as follows:

ArrayList<Map<String, Object>> sampleArray =   (ArrayList)myPremiumspaid.get("Data"); 
for(int x =0; x<sampleArray.size(); x++)
 {
    //sampleArray.get(x).get("YearMonth");
   listData.get(x).add(sampleArray.get(x).get("YearMonth"));
 }

Codename One's DefaultTableModel has an addRow method that accepts an array or series of Objects so just using:

((DefaultTableModel)tblModel).addRow("Cheese", "Pepperoni", "Black Olives");

Should work.

edited May 4, 2016 at 4:42

Shai Almog

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answered May 4, 2016 at 3:11

CrawlingKid

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3 Comments

Shai Almog Over a year ago

FYI added a small refinement to the answer at the bottom referring to DefaultTableModel in Codename One

Yung A Over a year ago

I managed to specify the size of listData array from the size of my returned data (sampleArray)

CrawlingKid Over a year ago

if you define the size of listData by the size of returned data of sampleArray, if you need to add more data from another object, you will not be able to extend the size of array because after creating the array, u cant extend it. So if you need dynamic growable size, you should use ArrayList.

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