Question

I’ve got 2 java Lists (Arraylists) of Floats, ListA and ListB of x and y coordinated which look like:

ListA = 10.1, 17.3, 30.0
ListB = 1.4, -14.7, 5.1

and I want to create a json object such that the two arraylists are consolidated into a single json object as:

[ { label: "A", data: [ [10.1, 1.4], [17.3, -14.7], [30.0, 5.1] ] }]

that I can plot using flot.

I’ve been looking at the Gson lib but I can’t see a concise way to do this – is there a simpler way than setting up loops for each key and manually appending “[ { …” etc ?

Thanks!

Answer 1

I think I understood what you need.
You are tryng to create the object structure to create the JSON in the format that you showed. Am I right? So, try something like:

// define a class to represent each graph
public class GraphData {

    private String label;
    private List<Float[]> data;

    // gets and sets to label and data

}

The lists of arrays of floats needs to be populated as (using listA and listB):

List<Float[]> yourFirstListOfData = new ArrayList<Float[]>();
for ( int i = 0; i < listA.size(); i++ ) {
    yourFirstListOfData.add( new Float[]{ listA.get(i), listB.get(i) } );
}

To generate JSON (in another class):

List<GraphData> graphList = new ArrayList<GraphData>();

GraphData graphData1 = new GraphData();
graphData1.setLabe1( "A" );
graphData1.setData( yourFirstListOfData );

GraphData graphData2 = new GraphData();
graphData2.setLabel( "B" );
graphData2.setData( yourSecondListOfData );

graphList.add(graphData1);
graphList.add(graphData2);

Gson gson = new Gson();
String json = gson.toJson( graphList );

// prints the generated json
System.out.println( json );