JFrame does not display correctly on small screens

As I said, you can achieve almost any kind of layout using just BorderLayout

and GridLayout

. Manage these two layout managers and you don't need the others. Here is my final version. Please refer to the tutorials for a more complete understanding of layout managers: https://docs.oracle.com/javase/tutorial/uiswing/layout/using.html

            import java.awt.BorderLayout;
            import java.awt.Color;
            import java.awt.Component;
            import java.awt.Dimension;
            import java.awt.GridLayout;

            import javax.swing.BorderFactory;
            import javax.swing.JButton;
            import javax.swing.JFrame;
            import javax.swing.JLabel;
            import javax.swing.JPanel;
            import javax.swing.JScrollPane;
            import javax.swing.JTextField;
            import javax.swing.JTree;
            import javax.swing.SwingConstants;
            import javax.swing.SwingUtilities;
            import javax.swing.WindowConstants;

            public class FrameDemo extends JFrame {
                private static final long serialVersionUID = 1L;

                public FrameDemo() {
                    super("Frame Demo");
                    setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

                    getContentPane().add(new NorthPanel(), BorderLayout.NORTH);
                    getContentPane().add(new CenterPanel(), BorderLayout.CENTER);
                    getContentPane().add(new SouthPanel(), BorderLayout.SOUTH);

                //          Toolkit tk = Toolkit.getDefaultToolkit();
                //          int xSize = ((int) tk.getScreenSize().getWidth());
                //          int ySize = ((int) tk.getScreenSize().getHeight());
                //          setSize(xSize,ySize);

                    pack();
                    setLocationRelativeTo(null);
                }

                public static void main(String[] args) {
                    SwingUtilities.invokeLater(new Runnable() {
                        public void run() {
                            JFrame frame = new FrameDemo();
                            frame.setVisible(true);
                        }
                    });
                } 
            }

            class NorthPanel extends JPanel {
                private static final long serialVersionUID = 1L;

                public NorthPanel() {
                    super(new BorderLayout());
                    setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));

                    add(getHeaderPanel(), BorderLayout.NORTH);
                    add(getButtonPanel(), BorderLayout.SOUTH);
                }

                private Component getHeaderPanel() {
                    JPanel panel = new JPanel(new GridLayout(2, 1));
                    panel.setBackground(Color.WHITE);

                    panel.add(new JLabel("XXXXXX Enterprises", SwingConstants.CENTER));
                    panel.add(new JLabel("XXX, Industria; Area - II, XXXXXXXXX", SwingConstants.CENTER));

                    return panel;
                }

                private Component getButtonPanel() {
                    JPanel panel = new JPanel(new BorderLayout());
                    panel.setBorder(BorderFactory.createEmptyBorder(10, 10, 0, 0));

                    JPanel buttons = new JPanel(new GridLayout(1, 2));
                    buttons.add(new JButton("Admin"));
                    buttons.add(new JButton("Exit"));

                    panel.add(buttons, BorderLayout.EAST);
                    return panel;
                }
            }

            class CenterPanel extends JPanel {
                private static final long serialVersionUID = 1L;

                private static final Dimension PANEL_SIZE = new Dimension(640, 480);

                public CenterPanel() {
                    super(new BorderLayout());
                    setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));

                    add(getSearchFieldsPanel(), BorderLayout.NORTH);
                    add(getResultsPanel(), BorderLayout.CENTER);
                }

                private Component getSearchFieldsPanel() {
                    JPanel panel = new JPanel(new BorderLayout());
                    panel.setBackground(Color.WHITE);

                    panel.add(new JLabel("Sales Inventory", SwingConstants.CENTER), BorderLayout.NORTH);
                    panel.add(getFieldsPanel(), BorderLayout.CENTER);
                    panel.add(getButtonPanel(), BorderLayout.SOUTH);

                    return panel;
                }

                private Component getResultsPanel() {
                    JPanel panel = new JPanel(new BorderLayout());

                    panel.add(getHeaderPanel(), BorderLayout.NORTH);
                    panel.add(new JScrollPane(new JTree()), BorderLayout.CENTER);
                    panel.add(getAnotherButtonPanel(), BorderLayout.SOUTH);

                    return panel;
                }

                private Component getHeaderPanel() {
                    JPanel panel = new JPanel(new BorderLayout());
                    panel.setBorder(BorderFactory.createEmptyBorder(10, 0, 10, 0));

                    JLabel label = new JLabel("Customers", SwingConstants.LEFT);
                    label.setOpaque(true);
                    label.setBackground(Color.WHITE);


                    panel.add(label, BorderLayout.NORTH);
                    return panel;
                }

                private Component getFieldsPanel() {
                    JPanel panel = new JPanel(new GridLayout(1, 4));

                    panel.add(new LabeledField("Name :  "));
                    panel.add(new LabeledField("Firm Name :  "));
                    panel.add(new LabeledField("City :  "));
                    panel.add(new LabeledField("Mobile :  "));

                    return panel;
                }

                private Component getButtonPanel() {
                    JPanel panel = new JPanel(new BorderLayout());
                    panel.setBorder(BorderFactory.createEmptyBorder(10, 10, 0, 0));
                    panel.setBackground(Color.WHITE);

                    JPanel buttons = new JPanel(new GridLayout(1, 2));
                    buttons.add(new JButton("Reset"));
                    buttons.add(new JButton("Search"));

                    panel.add(buttons, BorderLayout.EAST);
                    return panel;
                }

                private Component getAnotherButtonPanel() {
                    JPanel panel = new JPanel(new BorderLayout());
                    panel.setBorder(BorderFactory.createEmptyBorder(10, 10, 0, 0));
                    panel.setBackground(Color.WHITE);

                    JPanel buttons = new JPanel(new GridLayout(1, 2));
                    buttons.add(new JButton("Next"));

                    panel.add(buttons, BorderLayout.EAST);
                    return panel;
                }

                public Dimension getPreferredSize() {
                    return PANEL_SIZE;
                }

                public Dimension getMinimumSize() {
                    return PANEL_SIZE;
                }

                public Dimension getMaximumSize() {
                    return PANEL_SIZE;
                }
            }

            class SouthPanel extends JPanel {
                private static final long serialVersionUID = 1L;

                public SouthPanel() {
                    super(new GridLayout());

                    setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));

                    add(new JButton("Sales Inventory"));
                    add(new JButton("Customer"));
                    add(new JButton("Stock Inventory"));
                    add(new JButton("Reports"));
                }
            }

            class LabeledField extends JPanel {
                private static final long serialVersionUID = 1L;

                public LabeledField(String label) {
                    super(new BorderLayout());

                    setBackground(Color.WHITE);
                    add(getLabel(label), BorderLayout.WEST);
                    add(getEntry(), BorderLayout.CENTER);
                }

                private Component getLabel(String caption) {
                    JLabel label = new JLabel(caption, SwingConstants.RIGHT);
                    label.setPreferredSize(new Dimension(85, 25));
                    return label;
                }

                private Component getEntry() {
                    return new JTextField();
                }
            }

      

        
        
        
      

    

This is output

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.GridLayout;

import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextField;
import javax.swing.JTree;
import javax.swing.SwingConstants;
import javax.swing.SwingUtilities;
import javax.swing.WindowConstants;
import javax.swing.border.Border;
import javax.swing.border.CompoundBorder;

public class FrameDemo extends JFrame {
    private static final long serialVersionUID = 1L;

    public FrameDemo() {
        super("Frame Demo");
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

        getContentPane().add(new NorthPanel(), BorderLayout.NORTH);
        getContentPane().add(new CenterPanel(), BorderLayout.CENTER);
        getContentPane().add(new SouthPanel(), BorderLayout.SOUTH);

        //          Toolkit tk = Toolkit.getDefaultToolkit();
        //          int xSize = ((int) tk.getScreenSize().getWidth());
        //          int ySize = ((int) tk.getScreenSize().getHeight());
        //          setSize(xSize,ySize);

        pack();
        setLocationRelativeTo(null);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                JFrame frame = new FrameDemo();
                frame.setVisible(true);
            }
        });
    } 
}

class NorthPanel extends JPanel {
    private static final long serialVersionUID = 1L;

    public NorthPanel() {
        super(new BorderLayout());
        setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));

        add(getHeaderPanel(), BorderLayout.NORTH);
        add(getButtonPanel(), BorderLayout.SOUTH);
    }

    private Component getHeaderPanel() {
        JPanel panel = new JPanel(new GridLayout(2, 1));
        panel.setBackground(Color.WHITE);

        panel.add(new JLabel("XXXXXX Enterprises", SwingConstants.CENTER));
        panel.add(new JLabel("XXX, Industria; Area - II, XXXXXXXXX", SwingConstants.CENTER));

        return panel;
    }

    private Component getButtonPanel() {
        JPanel panel = new JPanel(new BorderLayout());
        panel.setBorder(BorderFactory.createEmptyBorder(10, 10, 0, 0));

        JPanel buttons = new JPanel(new GridLayout(1, 2));
        buttons.add(new JButton("Admin"));
        buttons.add(new JButton("Exit"));

        panel.add(buttons, BorderLayout.EAST);
        return panel;
    }
}

class CenterPanel extends JPanel {
    private static final long serialVersionUID = 1L;

    private static final Dimension PANEL_SIZE = new Dimension(640, 480);

    public CenterPanel() {
        super(new BorderLayout());
        setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));

        add(getSearchFieldsPanel(), BorderLayout.NORTH);
        add(new NewPanel(), BorderLayout.WEST);
        add(getResultsPanel(), BorderLayout.CENTER);
    }

    private Component getSearchFieldsPanel() {
        JPanel panel = new JPanel(new BorderLayout());
        panel.setBackground(Color.WHITE);

        panel.add(new JLabel("Sales Inventory", SwingConstants.CENTER), BorderLayout.NORTH);
        panel.add(getFieldsPanel(), BorderLayout.CENTER);
        panel.add(getButtonPanel(), BorderLayout.SOUTH);

        return panel;
    }

    private Component getResultsPanel() {
        JPanel panel = new JPanel(new BorderLayout());

        panel.add(getHeaderPanel(), BorderLayout.NORTH);
        panel.add(new JScrollPane(new JTree()), BorderLayout.CENTER);
        panel.add(getAnotherButtonPanel(), BorderLayout.SOUTH);

        return panel;
    }

    private Component getHeaderPanel() {
        JPanel panel = new JPanel(new BorderLayout());
        panel.setBorder(BorderFactory.createEmptyBorder(10, 0, 10, 0));

        JLabel label = new JLabel("Customers", SwingConstants.LEFT);
        label.setOpaque(true);
        label.setBackground(Color.WHITE);


        panel.add(label, BorderLayout.NORTH);
        return panel;
    }

    private Component getFieldsPanel() {
        JPanel panel = new JPanel(new GridLayout(1, 4));

        panel.add(new LabeledField("Name :  "));
        panel.add(new LabeledField("Firm Name :  "));
        panel.add(new LabeledField("City :  "));
        panel.add(new LabeledField("Mobile :  "));

        return panel;
    }

    private Component getButtonPanel() {
        JPanel panel = new JPanel(new BorderLayout());
        panel.setBorder(BorderFactory.createEmptyBorder(10, 10, 0, 0));
        panel.setBackground(Color.WHITE);

        JPanel buttons = new JPanel(new GridLayout(1, 2));
        buttons.add(new JButton("Reset"));
        buttons.add(new JButton("Search"));

        panel.add(buttons, BorderLayout.EAST);
        return panel;
    }

    private Component getAnotherButtonPanel() {
        JPanel panel = new JPanel(new BorderLayout());
        panel.setBorder(BorderFactory.createEmptyBorder(10, 10, 0, 0));
        panel.setBackground(Color.WHITE);

        JPanel buttons = new JPanel(new GridLayout(1, 2));
        buttons.add(new JButton("Next"));

        panel.add(buttons, BorderLayout.EAST);
        return panel;
    }

    public Dimension getPreferredSize() {
        return PANEL_SIZE;
    }

    public Dimension getMinimumSize() {
        return PANEL_SIZE;
    }

    public Dimension getMaximumSize() {
        return PANEL_SIZE;
    }
}

class SouthPanel extends JPanel {
    private static final long serialVersionUID = 1L;

    public SouthPanel() {
        super(new GridLayout());

        setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));

        add(new JButton("Sales Inventory"));
        add(new JButton("Customer"));
        add(new JButton("Stock Inventory"));
        add(new JButton("Reports"));
    }
}

class LabeledField extends JPanel {
    private static final long serialVersionUID = 1L;

    public LabeledField(String label) {
        super(new BorderLayout());

        setBackground(Color.WHITE);
        add(getLabel(label), BorderLayout.WEST);
        add(getEntry(), BorderLayout.CENTER);
    }

    private Component getLabel(String caption) {
        JLabel label = new JLabel(caption, SwingConstants.RIGHT);
        label.setPreferredSize(new Dimension(85, 25));
        return label;
    }

    private Component getEntry() {
        return new JTextField();
    }
}

class NewPanel extends JPanel {
    private static final long serialVersionUID = 1L;

    public NewPanel() {
        super(new BorderLayout());
        setBorder(BorderFactory.createEmptyBorder(10, 0, 0, 10));       
        add(getTopPanel(), BorderLayout.NORTH);
        add(new NewBottomPanel(), BorderLayout.CENTER);     
    }

    public Dimension getPreferredSize() {
        return new Dimension(350, 300);
    }

    private Component getTopPanel() {
        JPanel container = new JPanel(new BorderLayout());

        JPanel panel = new JPanel(new GridLayout(3,2));
        panel.add(new LabeledField("Design ID :  "));
        panel.add(new LabeledField("Thickness :  "));
        panel.add(new LabeledField("   Finish :  "));
        panel.add(new LabeledField(" Quantity :  "));
        panel.add(new LabeledField("     Rate :  "));
        panel.add(new LabeledField("     Size :  "));

        container.add(panel, BorderLayout.NORTH);
        container.add(getTopButtonPanel(), BorderLayout.SOUTH);

        return container;
    }

    private Component getTopButtonPanel() {
        JPanel container = new JPanel(new BorderLayout());
        container.setBorder(BorderFactory.createEmptyBorder(10, 0, 0, 0));

        container.setBackground(Color.WHITE);
        container.add(new JButton("Add Item"), BorderLayout.EAST);
        return container;
    }
}

class NewBottomPanel extends JPanel {
    private static final long serialVersionUID = 1L;

    public NewBottomPanel() {
        super(new BorderLayout());

        Border emptyBorder = BorderFactory.createEmptyBorder(10, 0, 0, 0);
        Border redLineBorder = BorderFactory.createLineBorder(Color.RED, 1);
        Border compounded = new CompoundBorder(emptyBorder, redLineBorder);
        setBorder(compounded);      
        setBackground(Color.WHITE);

        add(getTopPanel(), BorderLayout.NORTH);

    }

    private Component getTopPanel() {
        JPanel container = new JPanel(new BorderLayout());
        container.setBorder(BorderFactory.createEmptyBorder(10, 0, 0, 0));
        container.setBackground(Color.WHITE);

        JPanel panel = new JPanel(new GridLayout(3,2));
        panel.add(new LabeledField("Design ID :  "));
        panel.add(new LabeledField("Thickness :  "));
        panel.add(new LabeledField("   Finish :  "));
        panel.add(new LabeledField(" Quantity :  "));
        panel.add(new LabeledField("     Rate :  "));
        panel.add(new LabeledField("     Size :  "));

        container.add(panel, BorderLayout.NORTH);       
        return container;
    }   
}