How to construct an array of arrays from Resultset

Question

I am working on Google charts API and Google Visualization Candlestick Charts expects data to be an array of arrays for it to work .

For example the below format

[
[ "2011-08-01", 136.65, 136.96, 134.15, 136.49 ],
[ "2011-08-02", 135.26, 135.95, 131.50, 131.85 ],
[ "2011-08-05", 132.90, 135.27, 128.30, 135.25 ]
]

This is my SQL by which i am retrieving the data from database

String selectsql = "select current_day ,  open_val , high_val , low_val , close_val  from   historical_data where symbol_name = ?";
while(Rset.next())
            {
                String current_day =  SgxRset.getString("current_day");
                String open_val =  SgxRset.getString("open_val");
                String high_val =  SgxRset.getString("high_val");
                String low_val =  SgxRset.getString("low_val");
                String close_val =  SgxRset.getString("close_val");
            }

Could you please tell me how to construct how to construct an array of arrays ??

sample program

import java.util.ArrayList;
import java.util.List;

import org.json.JSONException;

public class TestJSON {

    public static void main(String[] args) throws JSONException {
        Employee emp1 = new Employee();
        emp1.setName("Ravi");
        emp1.setName("20");
        Employee emp2 = new Employee();
        emp2.setName("Kiran");
        emp2.setName("20");
        List<Employee> histList = new ArrayList<Employee>();

         Object[] arrayResultData = histList.toArray();

    }
}


public class Employee {

    String name ;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getAge() {
        return age;
    }
    public void setAge(String age) {
        this.age = age;
    }
    String age ;

}

I don't think this is an array of array. It has one string and others are float values. — pri
– pri, Commented Nov 5, 2015 at 13:28
You don't want an array of arrays if you don't know how many rows you will have, because you can't resize the array - you'd need an array list of arrays, or something similar. — Andy Turner
– Andy Turner, Commented Nov 5, 2015 at 13:29
What have you tried? What part are you stuck on? Return a JSON array of arrays, creating a data structure in Java? Something else? — Michael Lloyd Lee mlk
– Michael Lloyd Lee mlk, Commented Nov 5, 2015 at 13:32

Srijani Ghosh · Accepted Answer · 2015-11-05 14:06:44Z

1

Create a class which will held all these data together in an object like this with getters and setters:

 public class Data {
            private String current_day;
    private double open_val;
    private double high_val;
    private double low_val;
    private double close_val;

    public Data(String current_day, double open_val, double high_val,
            double low_val, double close_val) {
        this.current_day = current_day;
        this.open_val = open_val;
        this.high_val = high_val;
        this.low_val = low_val;
        this.close_val = close_val;
    }

    public String getCurrent_day() {
        return current_day;
    }

    public void setCurrent_day(String current_day) {
        this.current_day = current_day;
    }

    public double getOpen_val() {
        return open_val;
    }

    public void setOpen_val(double open_val) {
        this.open_val = open_val;
    }

    public double getHigh_val() {
        return high_val;
    }

    public void setHigh_val(double high_val) {
        this.high_val = high_val;
    }

    public double getLow_day() {
        return low_val;
    }

    public void setLow_day(double low_day) {
        this.low_val = low_day;
    }

    public double getClose_day() {
        return close_val;
    }

    public void setClose_day(double close_day) {
        this.close_val = close_day;
    }

    }

Now, store the data in array of objects which you are getting from SQL.

String selectsql = "select current_day ,  open_val , high_val , low_val ,close_val  from   historical_data where symbol_name = ?";
    List<Data> myList = new ArrayList(Data); 
    while(Rset.next())
                {
                    String current_day =  SgxRset.getString("current_day");
                    String open_val =  SgxRset.getString("open_val");
                    String high_val =  SgxRset.getString("high_val");
                    String low_val =  SgxRset.getString("low_val");
                    String close_val =  SgxRset.getString("close_val");

                    Data data = new Data(current_day,open_val,high_val,low_val,close_val);
                    myList.add(data);
                }

For reading data, you can write:

 String a = "[ ";
    for (int i = 0; i < myList.size(); i++) {
        String b = "[ \"" + myList.get(i).getCurrent_day() + "\" , "
                + myList.get(i).getOpen_val() + "],";
        if(i==myList.size() -1)
            a += b;
        else
            a += b+",";
    }
    a += " ]";

Now, for me the output is:

[ [ "2011-08-01" , 136.65],[ "2011-08-02" , 135.26] ]

edited Nov 5, 2015 at 14:06

answered Nov 5, 2015 at 13:40

Srijani Ghosh

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13 Comments

Pawan Over a year ago

thanks but its same thing know what erguant has mentioned ?? how is it different ??

Srijani Ghosh Over a year ago

Yeah, it is same, but, while I was writing the answer, some one has already answered.

Srijani Ghosh Over a year ago

I think, for creating an array of arrays is a illution here. You need to create a string which looks like an array of arrays. I have personally worked in google visualization. I think the edited code above will help you.

Srijani Ghosh Over a year ago

Thanks! Please let me know what happens!

Pawan Over a year ago

It created an empty array [ ]

|

ergonaut · Accepted Answer · 2015-11-05 13:39:40Z

1

I recommend a List. You don't know what your columns are and how many you have:

List<HistData> histList = new ArrayList<HistData>();
//.. query db
while(Rset.next()){
  HistData histData = new HistData();
  histData.setCurrentDay( SgxRset.getString("current_day"));
  histData.setOpenVal( SgxRset.getString("open_val"));
  histData.setHighVal( SgxRset.getString("high_val"));
  histData.setLowVal( SgxRset.getString("low_val"));
  histData.setCloseVal( SgxRset.getString("close_val"));
  histList.add(histData);
}

HistData is just a POJO, but you can change the datatypes in the bean and the SgxRset retrieval type, so you are not locked in to any array type. Using a List as opposed to an array provides more flexibility in case you are returning many results of unknown length.

public class HistData {
    public HistData(){}
    String currentDay;
    public setCurrentDay(String currentDay){
        this.currentDay = currentDay;
    }
    public getCurrentDay(){
        return currentDay;
    }
    // .. etc.
}

edited Nov 5, 2015 at 13:39

answered Nov 5, 2015 at 13:35

ergonaut

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2 Comments

Pawan Over a year ago

but still how to construct such type of array from List ??

Pawan Over a year ago

please see my edited part of my question i have created a sample part , how can i display that in form of what google charts expect ??

Rogerio Souza · Accepted Answer · 2015-11-05 13:40:54Z

Use a List and the toArray Method

String selectsql = "select current_day ,  open_val , high_val , low_val ,     close_val  from   historical_data where symbol_name = ?";

      List<String[]>resultData = new ArrayList<Stirng[]>();

        while(Rset.next())
                {
                    String[] array = new String[5];

                    array[0] =  SgxRset.getString("current_day");
                    array[1] =  SgxRset.getString("open_val");
                    array[2] =  SgxRset.getString("high_val");
                    array[3] =  SgxRset.getString("low_val");
                    array[4] =  SgxRset.getString("close_val");
                }

        Object[] arrayResultData = resultData.toArray();

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