Question

my java is rusty and I was wondering if someone could give me a code sample of how to do the following:

I have a result set from a database call that returns the following table:

object_id(int), marker_id(int), xpos(float), ypos(float)

the results are grouped by object_id such that you have something like this:

1023, 19, 0.2, 0.8
1023, 63, 0.2, 0.9
1023, 63, 0.2, 0.9
1072, 63, 0.2, 0.23
1072, 63, 0.2, 0.9
1072, 63, 0.2, 0.6
1012, 63, 0.2, 0.6
1012, 63, 0.2, 0.6


I was looking for the most effective way of generating two 2d double arrays such that
the first has

double[][] array1 = {
{0.2,0.8,0.2,0.9...},
{0.2,0.8,0.2,0.9...},
...}


each sub array contains the sequence x1,y1,x2,y2,x3,y3 for row1,row2,etc… for the corresponding object_id in the result set.

The second 2d array would contain:

double[][] array2 = {
{1.0},
{0.9},
{0.8},
...
{0.0}}


Where there’s an entry for each unique object_id and the first entry has 1.0 and the last entry has 0.0

The two arrays should have the same length since each entry represents an object_id

Hope that makes sense

Thanks

Answer 1

Edited Answer Below

“I need to transform it into arrays for input to another library. – user257543”

Well in order to do that, one approach is to turn the columns into an array and then combine them however you want.

    //get the size of the ResultSet
    myResultSet.last();
    int resultSetSize = myResultSet.getRow();
    //initialize your arrays to be joined
    int[] array1 = new int[resultSetSize];
    int[] array2 = new int[resultSetSize];
   //loop through the result so array1 will be the same as column1 of your table, etc.
    int count = 0;
    myResultSet.beforeFirst();
    while (myResultSet.next()){
        array1[count] = myResultSet.getInt("my column 1");
        array2[count] = myResultSet.getInt("my column 2");
        count++;
    }
    //declare rows and columns for easy code readability
    int row = 0;
    int column = 2;
    //set your combined array row and column lengths
    int[][] aCombined = new int[array1.length][column];
    //reset your column value to put array1 down column 0
    column = 0;
    for (int tempInt : array1){
        aCombined[row][column] = tempInt;
        row++;
    }
    //reset your row and go to the next column to do the same as above
    row = 0;
    column = 1;
    for (int tempInt : array2){
        aCombined[row][column] = tempInt;
        row++;
    }

Using the above-code, if your original arrays were:
int[] array1 = {1, 2, 3, 4};
int[] array2 = {5, 6, 7, 8};
aCombined would then result in [[1, 5], [2, 6], [3, 7], [4, 8]]

Which can be visualized as

• [column1/array1, column2/array2]

• [1, 5]

• [2, 6]

• [3, 7]

• [4, 8]

Original Answer Below

Why do you need to transform it into arrays? Why not just work with the result set itself?

For instance, if you need to get the marker_id of all of the objects with object_id of 1072, just:

public ArrayList getMarkerID(int objectId){
     ArrayList<int> myArrayList = new ArrayList<>();
     myResultSet.beforeFirst();
     while (myResultSet.next()){
         if (myResultSet.getInt("object_id") == objectId){
              myArrayList.add(myResultSet.getInt("marker_id"));
         }
      }
      return myArrayList;
  }

(I just typed this up real quick, and didn’t test it, so I may be missing a semi-colon or the logic may be off a little)