Question

I have a very simple Java program (see below). The GridLayout has 20 rows and 4 columns. As you know the elements are supposed to be added horizontally by (GridLayout) definition. However, I get the two elements (labels) placed one above the other, vertically.

I colored them and realised the labels take up the whole row, hence the vertical effect. But then I also used setSize(5,5) with each to make them smaller, however they still take up the whole row. Any advice as to why this happens and how to fix/set smaller size/etc?

public class Sam extends JFrame {

    public JButton btn_arr;
    public Container c;
    public JLabel[] lbl = new JLabel[20];


    public Sam()
    {
        c = getContentPane();
        c.setLayout(new GridLayout(20,4));
        lbl[1] = new JLabel("Column1");
        c.add(lbl[1]);

        lbl[2] = new JLabel("Column2");
        c.add(lbl[2]);

        show();     
    }

    public static void main(String[] args) 
    {
        Sam x = new Sam();
        x.setVisible(true);
        x.setSize(7500,4500);
    }

}

Answer 1

You’re only adding two components to the grid so they will fill it up. You need to add more components to the grid as placeholders so that it can place the original JLabels in their proper place, perhaps empty JLabels or JPanels.

As an aside, you should avoid setting the size of any Swing component. Your current size of 7500, 4500 is a bit on the large size.

As a second aside, perhaps you want to use a JTable instead here.

Edit: if you want a GridLayout with 4 columns and variable number of rows, use 0 for your GridLayout row constant:

c.setLayout(new GridLayout(0, 4));

e.g.,

import java.awt.*;
import javax.swing.*;

public class Sam extends JFrame {
   public static final int COLUMN_COUNT = 4;

   public JButton btn_arr;
   public Container c;
   public JLabel[] lbl = new JLabel[COLUMN_COUNT];

   public Sam() {
      c = getContentPane();
      c.setLayout(new GridLayout(0, COLUMN_COUNT));

      for (int i = 0; i < lbl.length; i++) {
         lbl[i] = new JLabel("Column " + (i + 1));
         c.add(lbl[i]);
      }

   }

   public static void main(String[] args) {
      Sam x = new Sam();
      x.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      x.pack();
      x.setLocationRelativeTo(null);
      x.setVisible(true);
      // x.setSize(7500,4500);
   }

}

But still I wonder if a JTable wouldn’t work better here.