public class JPanel
extends JComponent implements Accessible

java.lang.Object
 Ｌ java.awt.Component
     Ｌ java.awt.Container
         Ｌ javax.swing.JComponent
             Ｌ javax.swing.JPanel

JPanelクラスのオブジェクトを作成

JPanel
public JPanel()

JPanel panel = new JPanel();

フレームにパネルを追加

import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.Container;
import java.awt.BorderLayout;

class Sample extends JFrame{
  public static void main(String args[]){
    /* ... */
  }

  Sample(String title){
    /* ... */

    JPanel panel = new JPanel();

    Container contentPane = getContentPane();
    contentPane.add(panel, BorderLayout.CENTER);
  }
}

サンプルプログラム

import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.Container;
import java.awt.BorderLayout;
import java.awt.Color;

class SSample1_1 extends JFrame{
  public static void main(String args[]){
    SSample1_1 frame = new SSample1_1("タイトル");
    frame.setVisible(true);
  }

  SSample1_1(String title){
    setTitle(title);
    setBounds(100, 100, 300, 250);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    JPanel p1 = new JPanel();
    p1.setBackground(Color.BLUE);

    JPanel p2 = new JPanel();
    p2.setBackground(Color.ORANGE);

    Container contentPane = getContentPane();
    contentPane.add(p1, BorderLayout.NORTH);
    contentPane.add(p2, BorderLayout.SOUTH);
  }
}

サイズの設定

setPreferredSize
public void setPreferredSize(Dimension preferredSize)

JPanel panel = new JPanel();
panel.setPreferredSize(new Dimension(200, 100));

背景色の設定

setBackground
public void setBackground(Color bg)

JPanel panel = new JPanel();
panel.setBackground(Color.BLACK);

背景色の透明/非透明を設定

setOpaque
public void setOpaque(boolean isOpaque)

JPanel panel = new JPanel();
panel.setOpaque(false);

枠線の設定

setBorder
public void setBorder(Border border)

JPanel panel = new JPanel();

BevelBorder border = new BevelBorder(BevelBorder.RAISED);
panel.setBorder(border);

サンプルプログラム

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.BevelBorder;
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.Dimension;
import java.awt.Color;

class SSample2_1 extends JFrame{
  public static void main(String args[]){
    SSample2_1 frame = new SSample2_1("タイトル");
    frame.setVisible(true);
  }

  SSample2_1(String title){
    setTitle(title);
    setBounds(100, 100, 300, 250);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    setLayout(new FlowLayout());

    JPanel p1 = new JPanel();
    p1.setPreferredSize(new Dimension(100, 50));
    p1.setBackground(Color.BLUE);

    JPanel p2 = new JPanel();
    p2.setPreferredSize(new Dimension(50, 100));
    p2.setBackground(Color.ORANGE);

    BevelBorder border = new BevelBorder(BevelBorder.RAISED);
    p2.setBorder(border);

    Container contentPane = getContentPane();
    contentPane.add(p1);
    contentPane.add(p2);
  }
}

add
public Component add(Component comp)

JPanel panel = new JPanel();

JButton btn = new JButton();
panel.add(btn);

サンプルプログラム

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JLabel;
import javax.swing.JTextField;
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.Dimension;
import java.awt.Color;

class SSample3_1 extends JFrame{
  public static void main(String args[]){
    SSample3_1 frame = new SSample3_1("タイトル");
    frame.setVisible(true);
  }

  SSample3_1(String title){
    setTitle(title);
    setBounds(100, 100, 300, 250);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    setLayout(new FlowLayout());

    JPanel p = new JPanel();
    p.setPreferredSize(new Dimension(200, 100));
    p.setBackground(Color.ORANGE);

    JLabel label = new JLabel("入場者数");
    JTextField text = new JTextField(5);

    p.add(label);
    p.add(text);

    Container contentPane = getContentPane();
    contentPane.add(p);
  }
}

setLayout
public void setLayout(LayoutManager mgr)

JPanel panel = new JPanel();
panel.setLayout(new BorderLayout());

サンプルプログラム

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JButton;
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Color;

class SSample4_1 extends JFrame{
  public static void main(String args[]){
    SSample4_1 frame = new SSample4_1("タイトル");
    frame.setVisible(true);
  }

  SSample4_1(String title){
    setTitle(title);
    setBounds(100, 100, 300, 250);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    setLayout(new FlowLayout());

    JPanel p = new JPanel();
    p.setPreferredSize(new Dimension(200, 100));
    p.setBackground(Color.ORANGE);
    p.setLayout(new BorderLayout());

    JButton btn1 = new JButton("NORTH");
    JButton btn2 = new JButton("SOUTH");
    p.add(btn1, BorderLayout.NORTH);
    p.add(btn2, BorderLayout.SOUTH);

    Container contentPane = getContentPane();
    contentPane.add(p);
  }
}