JPanel

JPanel, a part of the Java Swing package, is a container that can store a group of components. The main task of JPanel is to organize components, various layouts can be set in JPanel which provide better organization of components. It does not have a title bar.

Following is the declaration for javax.swing.JPanel class −

public class JPanel extends JComponent implements Accessible

 Constructors of JPanel 

1. JPanel(): creates a new panel with a flow layout
2. JPanel(LayoutManager l): creates a new JPanel with specified layoutManager
3. JPanel(boolean isDoubleBuffered): creates a new JPanel with a specified buffering strategy
4. JPanel(LayoutManager l, boolean isDoubleBuffered): creates a new JPanel with specified layoutManager and a specified buffering strategy

Commonly used Functions of JPanel 

1. add(Component c): Adds a component to a specified container
2. setLayout(LayoutManager l): sets the layout of the container to the specified layout manager
3. updateUI(): resets the UI property with a value from the current look and feel.
4. setUI(PanelUI ui): sets the look and feel of an object that renders this component.
5. getUI(): returns the look and feel object that renders this component.
6. paramString(): returns a string representation of this JPanel.
7. getUIClassID(): returns the name of the Look and feel class that renders this component.
8. getAccessibleContext(): gets the AccessibleContext associated with this JPanel.

Ex:

// Java Program to Create a JPanel with a Border Layout and Adding Components to It

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

class solution extends JFrame {

            static JFrame f;

            static JButton b, b1, b2, b3;

            static JLabel l;

            public static void main(String[] args)

            {

                        f = new JFrame("panel");

                        l = new JLabel("panel label");

                        b = new JButton("button1");

                        b1 = new JButton("button2");

                        b2 = new JButton("button3");

                        b3 = new JButton("button4");

                        JPanel p = new JPanel(new BorderLayout());

 

                        p.add(b, BorderLayout.NORTH);

                        p.add(b1, BorderLayout.SOUTH);

                        p.add(b2, BorderLayout.EAST);

                        p.add(b3, BorderLayout.WEST);

                        p.add(l, BorderLayout.CENTER);

                        p.setBackground(Color.red);

                        f.add(p);

                        f.setSize(300, 300);

                        f.show();

            }

}