import javax.swing.*;
import java.awt.*;
public class JPanelDemo extends JFrame {
  private JPanel  DisplayPanel;
  private  JPanel InputPanel;
  private Container container;
  private JTextField tfResult;
  //面板中各按鈕的位置字符串。
  private  static final String Lables="789*456/123-0C=+";
  public JPanelDemo() {
    super("計算器") ;
    setSize(200,230);
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  }
  public void setLayout( ) {
    container=getContentPane();
    container.setLayout(new BorderLayout());
    DisplayPanel=new JPanel();
    DisplayPanel.setLayout(new BorderLayout());
    tfResult=new JTextField();
    DisplayPanel.add(tfResult,BorderLayout.CENTER);
    container.add(DisplayPanel,BorderLayout.NORTH);
    InputPanel=new JPanel();
    InputPanel.setLayout(new GridLayout(4,4));
    //創建按鈕并添加到輸入面板中。
    for(int i=0;i<Lables.length() ;i++){
      JButton btn=new JButton(Lables.substring(i,i+1));
      InputPanel.add(btn);
    }
    container.add(InputPanel,BorderLayout.CENTER);
  }
  public static void main(String[] args)  {
    JPanelDemo TestPanel = new JPanelDemo();
    TestPanel.setLayout();
    TestPanel.show();
  }
}