Access already running objects - Java

Question

   import java.awt.*;

   import javax.swing.*;
   import javax.swing.table.DefaultTableCellRenderer;
   import javax.swing.table.TableColumn;


   public class vasilisTable extends JFrame {

    Object[] split_data_l; 
    Object[][] split_data;
    Object [][] split_data_clone;
    Object [][] split_data_reverse;
    Object [][] split_data_reverse_num;
    String[] temp;
    private JTable table;
    private JPanel bottom_panel;
    private JLabel average;
    private JLabel max_dr;

    public vasilisTable(String name, String data, int choice)
    {
        super(name);
        setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); //the DISPOSE_ON_CLOSE    means that when we press the x button is will close only the table window and not the whole    programm
        //this.getAccessibleContext().setAccessibleName(name);
        //System.out.println(this.getAccessibleContext().getAccessibleName());
        setSize(800,600);



        String[] columnNames = {"Date", "Open","High","Low","Close",
                 "Volume", "Adjusted" };//defines the column names


        //------ Start of making the arrays that will be used as data for the table creation

        split_data_l = data.split( "\n" );
        int lngth = split_data_l.length;
        split_data = new Object[lngth-1][7];
        split_data_clone = new Object[lngth-1][7];
        split_data_reverse= new Object[lngth-1][7];
        split_data_reverse_num= new Object[lngth-1][7];
        double sum = 0;

        for(int k=1; k<split_data_l.length; k++) //initializing the three arrays with the data we got from the URLReader 
        {
            temp = split_data_l[k].toString().split(",");
            for (int l=0; l<temp.length; l++)
            {
                split_data[k-1][l] = temp[l];
                split_data_clone[k-1][l] = temp[l];
                split_data_reverse[k-1][l] = temp[l];
                split_data_reverse_num[k-1][l] = temp[l];
            }
        }



        for(int k=split_data_l.length-2; k>=1; k--) // making of the clone array that contains all the last column with colours
        {
            Double temp = Double.parseDouble(split_data[k][6].toString());
            Double temp1  = Double.parseDouble(split_data[k-1][6].toString());
            double check =temp-temp1;           

            if (check>0)
            {
                String color_temp = "<html><span style = 'color:red'>" + split_data_clone[k-1][6] +"</span></html>" ;
                split_data_clone[k-1][6] = color_temp;
            }
            else
            {
                String color_temp = "<html><span style = 'color:green'>" +split_data_clone[k-1][6]+"</span></html>" ;
                split_data_clone[k-1][6] = color_temp;
            }

        }

        int l = split_data_clone.length;
        int m = l-1;

        for (int i=0; i<l; i++) //making of the reversed array
        {
            for (int j = 0; j<=6; j++)
            {
                split_data_reverse[i][j]=split_data_clone[m][j];
            }
            m--;
        }

        m = l-1;

        for (int i=0; i<l; i++) //making of the reversed array
        {
            for (int j = 0; j<=6; j++)
            {
                split_data_reverse_num[i][j]=split_data[m][j];
            }
            m--;
        }





        //------ End of making the arrays that will be used as data for the table creation


      //------ Start of calculating the average
        for (int i=0; i<lngth-1; i++)
        {
            Double temp = Double.parseDouble(split_data[i][6].toString());
            sum = sum+temp;
            //System.out.println("turn "+i+" = "+split_data[i][6]);
        }

        float avg = (float) (sum/(lngth-1));
        avg = Round((float) avg,2);
        String avg_str;
        avg_str = "<html>Average: <b>"+avg+"</b></html>";
        //"<html><b>Average: </b></html>"



      //------ End of calculating the average


      //------ Start of Calculating the Maximal Drawdown

        double high=0;
        double low=100000000;
        double drawdown=0;
        double max_drawdown=0;
        int last_high=0;
        int last_low=0;

        for (int i=0; i<lngth-1; i++)
        {
            Double temp = Double.parseDouble(split_data_reverse_num[i][6].toString());
            //Double temp1 = Double.parseDouble(split_data[i+1][6].toString());

            if (temp>high)
            {
                high = temp;
                last_high = i;
                //System.out.println("max high = "+temp);
            }
            else
            {
                low = temp;
                last_low = i;
                //System.out.println("max low = "+temp);
            }
            if (last_low>last_high)
            {
                drawdown = high-low;
                //System.out.println("drawdown = "+drawdown);

            }
            if (drawdown>max_drawdown)
            {
                max_drawdown = drawdown;
            }
        } 

        //System.out.println("max dr = "+max_drawdown);
        String max_dr_str = "<html>Maximal Drawdown: <b>"+max_drawdown+"</b></html>";


      //------ End of Calculating the Maximal Drawdown



        average = new JLabel(avg_str);
        max_dr = new JLabel(max_dr_str);
        bottom_panel = new JPanel();
        String space = "       ";
        JLabel space_lbl = new JLabel(space);
        bottom_panel.add(average);
        bottom_panel.add(space_lbl);
        bottom_panel.add(max_dr);

        //-------- Start of table creation ---------

        if(choice==1)
        {
            table = new JTable(split_data_clone, columnNames);//creates an instance of the table with chronological order
        }else
        {
            table = new JTable(split_data_reverse, columnNames);//creates an instance of the table with reverse chronological order
        }

        TableColumn column = null;
        for (int i = 0; i < 7; i++) {
            column = table.getColumnModel().getColumn(i);
            if (i == 0) {
                column.setPreferredWidth(100); //third column is bigger
            } else if (i == 5) {
                column.setPreferredWidth(85); //third column is bigger
            }
            else if (i == 6) {
                column.setPreferredWidth(70); //third column is bigger
            }
            else {
                column.setPreferredWidth(50);
            }
        }
        table.setShowGrid(true);
        table.setGridColor(Color.black);

        //-------- End of table creation ---------







        JPanel table_panel = new JPanel (new BorderLayout());       
        JScrollPane table_container = new JScrollPane(table); // create a container where we will put the table
        //table.setFillsViewportHeight(true); // if the information are not enough it still fill the rest of the screen with cells

        table_panel.add(table_container, BorderLayout.CENTER);
        table_panel.add(bottom_panel, BorderLayout.SOUTH);
        //table_panel.add();

        setContentPane (table_panel);

        pack(); // here i pack the final result to decrease its dimensions


    }

    public float Round(float Rval, int Rpl) // this functions rounds the number to 2 decimal points
    {
    float p = (float)Math.pow(10,Rpl);
    Rval = Rval * p;
    float tmp = Math.round(Rval);
    return (float)tmp/p;
    }   


}

I am making an application which creates various instances of a class. These instances are actually some windows. After having create multiple of these windows, how can I access one of them and bring it in front? I know the .tofront() method, but how can I specify the window that I want to bring in front?

Above is the code that creates every window. My main problem is that after I have create e.g 5 windows, how can I access one of them?

ps

code that creates each window:

  if (sData != null) {
                    //System.out.println("Success, waiting response");

                    vasilisTable ftable = new vasilisTable(name, sData, choice);
                     hashMap.put(name, ftable);
                    ftable.setVisible(true);

                    //choice=2;

                  }

Normally, you'd keep a reference to the instance around in your program somewhere if you needed it again later. — Thilo, Mar 26 '12 at 02:50
When you mention windows, do you mean that you using Swing? Would be easier to answer if you can include some code samples of what you trying to achieve. — HackerMonkey, Mar 26 '12 at 02:53
Local variables or instance fields. `this.myWindow = new Window();` or `myWindows.add (new Window())` (a list) or `myWindows.put("x", new Window())` (a map). — Thilo, Mar 26 '12 at 02:55
@Thilo, but how can access a specific instance of the above class if there are multiple instances running at the same time? — Vasilis Nikolaou, Mar 26 '12 at 03:08

score 1 · Answer 1 · answered Mar 26 '12 at 03:13

1

My main problem is that after I have create e.g 5 windows, how can I access one of them?

You have to keep a reference to the relevant objects in variables or an array or a collection or something. The "bring it to the front" function needs to:

figure out what domain object needs to be brought to the front,
lookup its corresponding JFrame, and
call toFront() on it.

Java provides no built-in mechanisms for finding previously created instances of objects.

answered Mar 26 '12 at 03:13

Stephen C

698,415
94
811
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Quite there, just a few more hints if you could please: 1. How do I set the reference when I create the object? 2. Lets say that the reference is x. Should i just say x.tofront()? – Vasilis Nikolaou Mar 26 '12 at 03:23
1) Like this `Foo x = new Foo();` or if `x` is a `Foo[]` then `x[i] = new Foo();` and so on. 2) Yes. Of course `x` has to be in scope ... – Stephen C Mar 26 '12 at 03:57

score 1 · Answer 2 · edited Mar 26 '12 at 21:02

1

When you create your various instances of the above JFrame, you can keep track of the created instances, may be store them within a HashMap, then you can pick the right JFrame instance basing on its designated name and bring it to the front. Have a look at the below code for more illustration:

HashMap<String, VasilisTable> hashMap = new HashMap<String, VasilisTable>();

JFrame firstWindow = new VasilisTable("firstWindow",data, choice);
hashMap.put("firstWindow", firstWindow);

JFrame secondWindow = new VasilisTable("secondWindow",data, choice);
hashMap.put("secondWindow", secondWindow);

JFrame thirdWindow = new VasilisTable("thirdWindow",data, choice);
hashMap.put("thirdWindow", thirdWindow);

// To bring a certain window to the front
JFrame window = hashMap.get("firstWindow");
window.setVisible(true);
window.toFront();

edited Mar 26 '12 at 21:02

animuson

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answered Mar 26 '12 at 03:27

HackerMonkey

443
3
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One last thing, all the objects I create have the same name. Does it affect somehow the hashtabe? – Vasilis Nikolaou Mar 26 '12 at 03:38
I am afraid that you have to use different names for different windows, as subsequent calls to the put methods with the same key will have the result of replacing the previous value, as such if you use the same name in the above code all what you will end up having in the hashmap is the last object you created. The name can simply be any string, it doesn't have to be the same as the name value you are passing to the constructor of the VasilisTable – HackerMonkey Mar 26 '12 at 03:41
the problem is that the every window is created when I press a button so it has to have the same name. look above the code that creates every window. – Vasilis Nikolaou Mar 26 '12 at 03:52
You can declare an integer outside the if statement, increment it each time a new window is invoked and use it as a postfix to the hashmap key name – HackerMonkey Mar 26 '12 at 04:06
thank u! I tried it and works fine! Thank u very much once again! – Vasilis Nikolaou Mar 26 '12 at 04:09

score 0 · Answer 3 · edited May 23 '17 at 10:08

Are these JFrame or JWindow objects? If they are you can call -

jframe.setVisible(true);
jframe.toFront();

This is something interesting I found at the API doc.

Places this Window at the top of the stacking order and shows it in front of any other Windows in this VM. No action will take place if this Window is not visible. Some platforms do not allow Windows which own other Windows to appear on top of those owned Windows. Some platforms may not permit this VM to place its Windows above windows of native applications, or Windows of other VMs. This permission may depend on whether a Window in this VM is already focused. Every attempt will be made to move this Window as high as possible in the stacking order; however, developers should not assume that this method will move this Window above all other windows in every situation.

I would recommend you to check out these answers as well.

Access already running objects - Java

3 Answers3