Problem in Buttons ...

[LogicBrix]

there's a little problem in my code ... But theres n

when i click the buttons i got this message ....

Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: empty String
at sun.misc.FloatingDecimal.readJavaFormatString(Floa tingDecimal.java:994)
at java.lang.Double.parseDouble(Double.java:510)
at HotelBill.actionPerformed(HotelBill.java:265)
at javax.swing.AbstractButton.fireActionPerformed(Abs tractButton.java:1995)
at javax.swing.AbstractButton$Handler.actionPerformed (AbstractButton.java:2318)
at javax.swing.DefaultButtonModel.fireActionPerformed (DefaultButtonModel.java:387)
at javax.swing.DefaultButtonModel.setPressed(DefaultB uttonModel.java:242)
at javax.swing.plaf.basic.BasicButtonListener.mouseRe leased(BasicButtonListener.java:236)
at java.awt.Component.processMouseEvent(Component.jav a:6038)
at javax.swing.JComponent.processMouseEvent(JComponen t.java:3260)
at java.awt.Component.processEvent(Component.java:580 3)
at java.awt.Container.processEvent(Container.java:205 8)
at java.awt.Component.dispatchEventImpl(Component.jav a:4410)
at java.awt.Container.dispatchEventImpl(Container.jav a:2116)
at java.awt.Component.dispatchEvent(Component.java:42 40)
at java.awt.LightweightDispatcher.retargetMouseEvent( Container.java:4322)
at java.awt.LightweightDispatcher.processMouseEvent(C ontainer.java:3986)
at java.awt.LightweightDispatcher.dispatchEvent(Conta iner.java:3916)
at java.awt.Container.dispatchEventImpl(Container.jav a:2102)
at java.awt.Window.dispatchEventImpl(Window.java:2429 )
at java.awt.Component.dispatchEvent(Component.java:42 40)
at java.awt.EventQueue.dispatchEvent(EventQueue.java: 599)
at java.awt.EventDispatchThread.pumpOneEventForFilter s(EventDispatchThread.java:273)
at java.awt.EventDispatchThread.pumpEventsForFilter(E ventDispatchThread.java:183)
at java.awt.EventDispatchThread.pumpEventsForHierarch y(EventDispatchThread.java:173)
at java.awt.EventDispatchThread.pumpEvents(EventDispa tchThread.java:168)
at java.awt.EventDispatchThread.pumpEvents(EventDispa tchThread.java:160)
at java.awt.EventDispatchThread.run(EventDispatchThre ad.java:121)



here my whole code

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class HotelBill extends JFrame implements ActionListener{
	

		
      
        JButton btn = new JButton();
        JButton b = new JButton("Check the room?");
        	
        JButton btn2 = new JButton();
        JButton b2 = new JButton("Check the room?");
        	
        JButton btn3 = new JButton();
        JButton b3 = new JButton("Check the room?");
        
        JButton btn4 = new JButton();
        JButton b4 = new JButton("Check the room?");		
        
        JButton btn5 = new JButton();
        JButton b5 = new JButton("Check the room?");	
   		
   		JButton btn6 = new JButton();
        JButton b6 = new JButton("Check the room?");
   
   		JButton btn7 = new JButton();
        JButton b7 = new JButton("Check the room?");
        	
        JButton btn8 = new JButton();
        JButton b8 = new JButton("Check the room?");
        		
   		JButton btn9 = new JButton();
        JButton b9 = new JButton("Check the room?");
        
        
        
        	
        JTextField txt = new JTextField();//Hotel Name
        JTextField txt2 = new JTextField();//Price
    //    JTextField txt3 = new JTextField();//Total
        JTextField DoN = new JTextField();//Day or night
        JTextField txt5 = new JTextField();//Quantity
       
       
       
       
       //Buttons Images ////////////////////
       Icon ic = new ImageIcon("image2/Economy Room.jpg  ");
       Icon i = new ImageIcon("image2/Economy Room2.jpg   ");
       
       Icon ic2 = new ImageIcon("image2/Stan.jpg  ");
       Icon i2 = new ImageIcon("image2/Stan2.jpg  ");
       
       Icon ic3 = new ImageIcon("image2/Deluxe.jpg  ");
       Icon i3 = new ImageIcon("image2/Deluxe2.jpg  ");
       
       Icon ic4 = new ImageIcon("image2/Suit.jpg  ");
       Icon i4 = new ImageIcon("image2/Suit2.jpg");
       
       Icon ic5 = new ImageIcon("image2/VIP.jpg  ");
       Icon i5 = new ImageIcon("image2/VIP2.jpg ");
       
       Icon ic6 = new ImageIcon("image2/Pres.jpg  ");
       Icon i6 = new ImageIcon("image2/Pres2.jpg ");
       
       Icon ic7 = new ImageIcon("image2/Hos.jpg  ");
       Icon i7 = new ImageIcon("image2/Hos2.jpg ");
       
       Icon ic8 = new ImageIcon("image2/Pent.jpg  ");
       Icon i8 = new ImageIcon("image2/Pent2.jpg");
       
       Icon ic9 = new ImageIcon("image2/Per.jpg  ");
       Icon i9 = new ImageIcon("image2/Per2.jpg  ");
       
       //////////////////////////////////////////////////////
       
       ImageIcon icon = new ImageIcon("image2/HotelBill.jpg");
        JLabel BG = new JLabel(icon);
        
        Font font = new Font("Times New Roman",Font.BOLD,14);
        
        	
        	
        	
   		
    public HotelBill() {
    	setLayout(null);
    	
    	//Bounds///////////////////////
    	btn.setBounds(50,200,200,40);
    	b.setBounds(50,250,200,20);
    	
    	btn2.setBounds(250,200,200,40);
    	b2.setBounds(250,250,200,20);
   	
    	btn3.setBounds(450,200,200,40);
    	b3.setBounds(450,250,200,20);
     
    	btn4.setBounds(50,300,200,40);
    	b4.setBounds(50,350,200,20);
    		
    	btn5.setBounds(250,300,200,40);
    	b5.setBounds(250,350,200,20);
    	
    	btn6.setBounds(450,300,200,40);
    	b6.setBounds(450,350,200,20);
    	
    	btn7.setBounds(50,400,200,40);
    	b7.setBounds(50,450,200,20);
    	
    	btn8.setBounds(250,400,200,40);
    	b8.setBounds(250,450,200,20);
    	
    	btn9.setBounds(450,400,200,40);
    	b9.setBounds(450,450,200,20);
    	
    	DoN.setBounds(720,500,100,25);
    	
   		txt.setBounds(720,200,200,40);
    	txt2.setBounds(720,280,200,40);
    //	txt3.setBounds(720,463,200,40);
    //	txt4.setBounds(720,537,200,40);
    	txt5.setBounds(720,388,150,25);
    	
    	
    	BG.setBounds(0,0,1000,700);
    	
    	////////////////////////////////
    	
    	//Buttons iCons ///////////
    	
    	btn.setIcon(ic);
    	btn.setRolloverIcon(i);
    	
    	btn2.setIcon(ic2);
    	btn2.setRolloverIcon(i2);
    	
    	btn3.setIcon(ic3);
    	btn3.setRolloverIcon(i3);
    	
    	btn4.setIcon(ic4);
    	btn4.setRolloverIcon(i4);
    	
    	btn5.setIcon(ic5);
    	btn5.setRolloverIcon(i5);
    	
    	btn6.setIcon(ic6);
    	btn6.setRolloverIcon(i6);
    	
    	btn7.setIcon(ic7);
    	btn7.setRolloverIcon(i7);
    	
    	btn8.setIcon(ic8);
    	btn8.setRolloverIcon(i8);
    	
    	btn9.setIcon(ic9);
    	btn9.setRolloverIcon(i9);
    	
    	
    	///////////////////////////////////////////
    	
    	
   
    	
    	
    	
    	
    	
    	
    	
    	//////////////////////////////////////
    	
    	//Layout///////////////
    	add(btn);
    	add(b);
    	add(btn2);
    	add(b2);
    	add(btn3);
    	add(b3);
    	add(btn4);
    	add(b4);
    	add(btn5);
    	add(b5);
    	add(btn6);
    	add(b6);
    	add(btn7);
    	add(b7);
    	add(btn8);
    	add(b8);
    	add(btn9);
    	add(b9);
    	
    	
    	add(DoN);
    	
    	
    	
    	add(BG);
    	
    	add(txt);
    	txt.setFont(font);
    	add(txt2);
    	txt2.setFont(font);
    //	add(txt3);
    //	txt3.setFont(font);
    //	add(txt4);
    //	txt4.setFont(font);
    	add(txt5);
    	txt5.setFont(font);
    	/////////////////////////
    	
    	
    	//Handler///////////////
    	btn.addActionListener(this);
    	b.addActionListener(this);
    	
    	btn2.addActionListener(this);
    	b2.addActionListener(this);
    	
    	btn3.addActionListener(this);
    	b3.addActionListener(this);
    	
    	btn4.addActionListener(this);
    	b4.addActionListener(this);
    	
    	btn5.addActionListener(this);
    	b5.addActionListener(this);
    	
    	btn6.addActionListener(this);
    	b6.addActionListener(this);
    	
    	btn7.addActionListener(this);
    	b7.addActionListener(this);
    	
    	btn8.addActionListener(this);
    	b8.addActionListener(this);
    	
    	btn9.addActionListener(this);
    	b9.addActionListener(this);
    	
    	
    	/////////////////////////////
    	
    	setSize(1000,700);
    	setVisible(true);
    	setResizable(false);
    	setDefaultCloseOperation(EXIT_ON_CLOSE);
    }
    
     public void actionPerformed (ActionEvent e ){
     	
     	double Eco = 39000;
     	double Stand = 27000;
     	double DL = 54000;
     	double Sui = 25000;
     	double vi = 65000;
     	double pres = 75000;
     	double hosp = 50000;
     	double ph = 80000;
     	double perf = 55000;
     	
     	
     	double num1 = Double.parseDouble(txt.getText());                 //  if i erase this code.. 
		double num2 = Double.parseDouble(txt2.getText());       //   i dont get that message and my program run properly ,, i think the problem is in here
		
      
     	
     	if(e.getSource() == btn){
     		txt.setText("Economy Room");
     		txt2.setText("39,000");
     		
     		
     	}
     	else if(e.getSource() == btn2){
     		txt.setText("Standard Room");
     		txt2.setText("27,000");
     		
     	}
     	else if(e.getSource() == btn3){
     		txt.setText("De Luxe");
     		txt2.setText("54,000");
     		
     	}
     	else if(e.getSource() == btn4){
     		txt.setText("Suite Room");
     		txt2.setText("25,000");
     		
     	}
     	else if(e.getSource() == btn5){
     		txt.setText("V.I.P Room");
     		txt2.setText("65,000");
     		
     	}
     	else if(e.getSource() == btn6){
     		txt.setText("Presidential Room");
     		txt2.setText("75,000");
     		
     	}
     	else if(e.getSource() == btn7){
     		txt.setText("Hospitality Suite");
     		txt2.setText("50,000");
     		
     	}
     	else if(e.getSource() == btn8){
     		txt.setText("Pent House");
     		txt2.setText("80,000");
     		
     	}
     	else if(e.getSource() == btn9){
     		txt.setText("Perfected Room");
     		txt2.setText("55,000");
     		
     	}
     	
   //////////////////////////////////////////
   
   			
     	
     	
     	
     	
     	
     	
     	
     	
     	
     	
     	
     }
   
   
   
    public static void main(String[] args) {
        HotelBill hb = new HotelBill();
    }
}

[Norm]

Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: empty String
at sun.misc.FloatingDecimal.readJavaFormatString(Floa tingDecimal.java:994)
at java.lang.Double.parseDouble(Double.java:510)
at HotelBill.actionPerformed(HotelBill.java:265)

At line 265 you need to test if the String you are trying to parse is empty before trying to parse it.
See the String class for methods for testing it.