B4J Question For Each statement difference between B4J and B4A?

[PaulMeuris]

Hi,
I am working on a B4X app and there seems to be a difference in the result after compilation with B4J and B4A.
The source code is in both cases the same (in B4XMainPage).
Here is the code snippet in question:

            Dim hoofd As Map = parser.NextObject
            Dim items As List = hoofd.Get("categories")
            For i = 0 To items.Size-1
                Dim rec As Map = items.Get(i)
                If i = 0 Then
                    sb.Append("<tr>").Append(CRLF)
                    For Each key As String In rec.Keys
                        Log("key = " & key)
                        sb.Append("<th>").Append(key).Append("</th>")
                    Next
                    sb.Append("</tr>").Append(CRLF)
                End If

In B4J the logs give the following result:

In B4A the logs give the following result:

The data comes from an online database and is in both cases the same (JSON string).
Why is the order of the column headers different?

Greetings,
Paul.

 

[Erel]

Moved to the questions forum.

The order of map keys, returned by the json parser is not determined. There are very rare cases where the order is important.

 

[Sandman]

There are very rare cases where the order is important.

I would go even further and say that if the order in a map is important, then that map is poorly designed.

(I'm willing to listen if somebody wants to change my mind.)

 

[PaulMeuris]

So the B4J Java Map implementation is different from the B4A Java Map implementation?

 

[OliverA]

I would go even further and say that if the order in a map is important, then that map is poorly designed.

In JSON, if you want to preserve the order, one should use an array (so yes, if order is important, it is not a very well designed JSON structure)

 

[PaulMeuris]

Thank you Erel and Sandman for your quick reply. I tried a different approach...
A JSON object can consist of an object of objects OR an array of arrays.
Using indexed arrays (and not associative arrays or key/value maps) to produce a JSON object results in a consistent way to order the columns.
An example:

        Log(j.GetString)
        Dim parser As JSONParser
        parser.Initialize(j.GetString)
        Dim hoofd As List = parser.NextArray
        Dim lst As List = hoofd.Get(0)
        Log(lst)
        sb.Append("<tr>").Append(CRLF)
        For i = 0 To lst.Size - 1
            sb.Append("<th>").Append(lst.Get(i)).Append("</th>")
        Next
        sb.Append("</tr>").Append(CRLF)
        sb.Append("<tr>")
        For i = 1 To hoofd.Size - 1
            Dim rec As List = hoofd.Get(i)
            Log(rec)
            For x = 0 To rec.Size - 1
                sb.Append("<td>").Append("<a href='http://").Append(rec.Get(x)).Append(".").Append("categories").Append(".local'>").Append(rec.Get(x)).Append("</a>").Append("</td>")               
            Next
            sb.Append("</tr>").Append(CRLF)
        Next

And the logs show the same results...
B4J log:

B4A log:

And the result in a webview:

So in my future apps I will go with this approach...

 

[PaulMeuris]

In JSON, if you want to preserve the order, one should use an array (so yes, if order is important, it is not a very well designed JSON structure)

Thank you OliverA.
I also came up with that solution...

 

[aeric]

I would go even further and say that if the order in a map is important, then that map is poorly designed.

(I'm willing to listen if somebody wants to change my mind.)

The order is not important for machine to read, I mean json parser but I found it is better for my eyes as a human to expect a consistent format.

 

[PaulMeuris]

Thank you Aeric.
Consistency avoids confusion...