How to show my button??

Question

well, Im a newbie to java and im trying to make a calculator, but can any1 help me to show the button on the window, the application can run but no button were shown.. i wonder what code should i add to the main method ..
Here is the code:
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
public class BC extends JFrame
     JButton B1       =new JButton("1");
     JButton B2       =new JButton("2");
     JButton B3       =new JButton("3");
     JButton B4       =new JButton("4");
     JButton B5       =new JButton("5");
     JButton B6       =new JButton("6");
     JButton B7       =new JButton("7");
     JButton B8       =new JButton("8");
     JButton B9       =new JButton("9");
     JButton B0       =new JButton("0");
     JButton BPlus     =new JButton("+");
     JButton BMinus    =new JButton("-");
     JButton BDivide   =new JButton("/");
     JButton BMultiply =new JButton("*");
     JButton BEqual    =new JButton("=");
     JButton BClear    =new JButton("C");
     JButton BBackspace=new JButton("Backspace");
     JButton BSqrt     =new JButton("sqrt");
     JButton BPosMin   =new JButton("+/-");
     JButton BPoint    =new JButton(".");
     JPanel PButton    =new JPanel();
     Container contain;
     public BC()
     public void ButtonConfiguration()
     PButton.setLayout(new GridLayout(4,5,2,2));
PButton.add(B1);
     public static void main(String args[])
     BC calculator=new BC();
     calculator.setTitle("Butcher's Calculator");
     calculator.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
     calculator.setSize(300,350);                    
     calculator.setResizable(false);          
     calculator.setVisible(true);                    
     

Answer 1

import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
public class BC extends JFrame
     JButton B1     =new JButton("1");
     JButton B2     =new JButton("2");
     JButton B3     =new JButton("3");
     JButton B4     =new JButton("4");
     JButton B5     =new JButton("5");
     JButton B6     =new JButton("6");
     JButton B7     =new JButton("7");
     JButton B8     =new JButton("8");
     JButton B9     =new JButton("9");
     JButton B0     =new JButton("0");
     JButton BPlus =new JButton("+");
     JButton BMinus =new JButton("-");
     JButton BDivide =new JButton("/");
     JButton BMultiply =new JButton("*");
     JButton BEqual =new JButton("=");
     JButton BClear =new JButton("C");
     JButton BBackspace=new JButton("Backspace");
     JButton BSqrt =new JButton("sqrt");
     JButton BPosMin =new JButton("+/-");
     JButton BPoint =new JButton(".");
     JPanel PButton =new JPanel();
     Container contain= getContentPane();
     public BC()
     PButton.setLayout(new GridLayout(4,5,2,2));
     PButton.add(B1);
     getContentPane().add(PButton);
     this.setSize(700,550);
     this.setVisible(true);
     public void ButtonConfiguration()
     public static void main(String args[])
     BC calculator=new BC();
     calculator.setTitle("Butcher's Calculator");
     calculator.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}