Retrieve Multiple value from an arraylist in java

Question

I am using ArrayList to Store Time,Bid and, ASK value from the database. And I am unable to access the data from Arraylist in form of row wise like database. how can I do it.

Here is the code:-

List<String> graphData=new ArrayList<String>();
 stmt = c.createStatement();
                rs = stmt.executeQuery( "SELECT TIME,BID,ASK FROM '"+title+"' ;" );
                System.out.println("Opened database successfully 20");
                List<Double> buyMap=new ArrayList<Double>();
                double buy_avg=0.0, bid=0.0,   temp_profit, cum_prof=0;
                while(rs.next()){
                     i++;
                    graphData.add(rs.getString(1));
                    graphData.add(df.format(rs.getFloat(2)));
                    graphData.add(df.format(rs.getFloat(3)));
                }

Now how can I get the data from graphData. Because I have to put these value in graph.

christopher · Accepted Answer · 2014-02-13 13:17:15Z

2

Ah, good lord just create an Object.

Example

public class Buy {
    private String firstValue;
    private String secondValue;
    private String thirdValue;
}

Then create a new Buy object with each row from the database..

graphData.add(new Buy(rs.getString(1), df.format(rs.getFloat(2)), df.format(rs.getFloat(3)));

Now you can access it in a pretty way, rather than jumping through an ArrayList in increments of 3.

answered Feb 13, 2014 at 13:17

christopher

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Comments

peter.petrov · Accepted Answer · 2014-02-13 13:15:34Z

1

You can do this:

for (int i=0; i<graphData.size(); i+=3){
   // get elem at i
   // get elem at i+1
   // get elem at i+2
}

But I would recommend you create some bean/POJO object and populate it with
the 3 values from each rs row. Then you add the bean objects to graphData.

answered Feb 13, 2014 at 13:15

peter.petrov

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Comments

npinti · Accepted Answer · 2014-02-13 13:24:16Z

How about using a list of lists? In this way, each list would represent a row in the database:

List<List<String>> graphData=new ArrayList<List<String>>();
 stmt = c.createStatement();
                rs = stmt.executeQuery( "SELECT TIME,BID,ASK FROM '"+title+"' ;" );
                System.out.println("Opened database successfully 20");
                List<Double> buyMap=new ArrayList<Double>();
                double buy_avg=0.0, bid=0.0,   temp_profit, cum_prof=0;
                while(rs.next()){
                     i++;
                    List<String> row = new ArrayList<String>();
                    row.add(rs.getString(1));
                    row.add(df.format(rs.getFloat(2)));
                    row.add(df.format(rs.getFloat(3)));
                    graphData.add(row)
                }

To access the data in a row like manner (akin to how they are stored in the database), you could do something like so:

for(List<String> db : graphData)
{
    System.out.println("TIME: " + db.get(0) + " BID " + db.get(1) + " ASK " + db.get(2));
}

Ashish Ratan · Accepted Answer · 2014-02-13 13:15:53Z

Your code:

 List<String> graphData=new ArrayList<String>();
   stmt = c.createStatement();
            rs = stmt.executeQuery( "SELECT TIME,BID,ASK FROM '"+title+"' ;" );
            System.out.println("Opened database successfully 20");
            List<Double> buyMap=new ArrayList<Double>();
            double buy_avg=0.0, bid=0.0,   temp_profit, cum_prof=0;
            while(rs.next()){
                 i++;
                graphData.add(rs.getString(1));
                graphData.add(df.format(rs.getFloat(2)));
                graphData.add(df.format(rs.getFloat(3)));
            }

retrieve data from list:

  for (String string : graphData) {
   System.out.println(string); // prints the values of the list
  }

StephaneM · Accepted Answer · 2014-02-13 13:22:23Z

Why don't you create a class to hold your data?

public class MyData {
private String field1;
private String field2;
private String field3;
public MyData( String f1, String f2, String f3) {
field1=f1;
field2=f2;
field3=f3;
}

// Add getters }

Then read data this way:

List<MyData> graphData=new ArrayList<MyData>();
 stmt = c.createStatement();
                rs = stmt.executeQuery( "SELECT TIME,BID,ASK FROM '"+title+"' ;" );
                System.out.println("Opened database successfully 20");
                List<Double> buyMap=new ArrayList<Double>();
                double buy_avg=0.0, bid=0.0,   temp_profit, cum_prof=0;
                while(rs.next()){
                     i++;
                    graphData.add(new MyData( rs.getString(1), df.format(rs.getFloat(2)), df.format(rs.getFloat(3)));
                }

and read it this way:

for ( MyData data : graphData )
{
   // do something with data
}

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