Swing doesn't respect my GridLayout Rows x Columns definition. How to fix?

Question

I have been trying to resolve this without success. How to make JPanel p respect the defined GridLayout? All I get is the first row containing 3 panels but not 4 as I've told Java to perform.

What's the necessary voodoo (or knowledge to my ignorance), to make it work?

package temp2;

import java.awt.Dimension;
import java.awt.GridLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;


public class Temp2 {

    public static void main(String[] args) {

        JFrame f = new JFrame();
        JPanel p = new JPanel();  
    //  GridLayout flow = new GridLayout(1, 5); --> With this I get a row with 5 jpanels
        GridLayout flow = new GridLayout(2, 4); // --> Why it doenst work? I want 4 
                                                // jpanels in the first row and 
                                                // subsequent one on the next row
                                                // --> Why it doesnt respect my code?
        p.setLayout(flow);
      // p.setSize(800,800); // --> This doesnt make any difference on final result either
      //  p.setPreferredSize(new Dimension(800,800));  // --> This doesnt make any
                                                      // difference on final result either
        p.setMinimumSize(new Dimension(800,800));

        JPanel x1 = new JPanel();     
        x1.setPreferredSize(new Dimension(50,30)); // --> It doesnt respect these preferences
        x1.setMaximumSize(new Dimension(50,30)); // --> It doesnt respect this maximum
        x1.setBorder(javax.swing.BorderFactory.createEtchedBorder());

        JPanel x2 = new JPanel();       
        x2.setPreferredSize(new Dimension(50,30)); // --> It doesnt respect these preferences
        x2.setMaximumSize(new Dimension(50,30)); // --> It doesnt respect this maximum
        x2.setBorder(javax.swing.BorderFactory.createEtchedBorder());

        JPanel x3 = new JPanel();      
        x3.setPreferredSize(new Dimension(50,30)); // --> It doesnt respect these preferences
        x3.setMaximumSize(new Dimension(50,30)); // --> It doesnt respect this maximum
        x3.setBorder(javax.swing.BorderFactory.createEtchedBorder());

        JPanel x4 = new JPanel();      
        x4.setPreferredSize(new Dimension(50,30)); // --> It doesnt respect these preferences
        x4.setMaximumSize(new Dimension(50,30));  // --> It doesnt respect this maximum      
        x4.setBorder(javax.swing.BorderFactory.createEtchedBorder());

        JPanel x5 = new JPanel();       
        x4.setMaximumSize(new Dimension(50,30)); // --> It doesnt respect these preferences
        x5.setPreferredSize(new Dimension(50,30)); // --> It doesnt respect this maximum 
        x5.setBorder(javax.swing.BorderFactory.createEtchedBorder());

         p.add(x1);
         p.add(x2);
         p.add(x3);
         p.add(x4);
         p.add(x5);

         f.getContentPane().add(p, "Center");

         f.setSize(800, 800);
         f.setVisible(true);
         p.updateUI();

        }   
    }

As this is my first StackOverflow question I'm trying to follow the rules strictly:

Be specific: I want GridLayout to respect row x columns definition

What my final purpose: Show 4 panels in the first row and subsequent one on the second row.

Make it relevant to others: That's why this code is didactic, repeating all the panel declarations so newcomers (and me) can understand all the code and focuses exclusively on the GridLayout issue.

Answer 1

    GridLayout flow = new GridLayout(2, 4); // --> Why it doenst work? I want 4 
                                            // jpanels in the first row and 
                                            // subsequent one on the next row
                                            // --> Why it doesnt respect my code?

Like this?

Use instead:

    GridLayout flow = new GridLayout(0,4);

Quoting the docs for the constructor:

Creates a grid layout with the specified number of rows and columns. All components in the layout are given equal size.

One, but not both, of rows and cols can be zero, which means that any number of objects can be placed in a row or in a column.