not a number exception and zero division exception

[tc123123]

Hello Im very new to all of this but studying computing at university basically I need help with two things ( I have to use Eclipse Helios) the first being to create my own NotANumberException which should be thrown/caught if the user enters a letter and then presses an action key e.g. +,- etc the second thing is to create my own ZeroDivisionException to handle the situation if a user tries to divide by zero. I've been creating a calculator and calculator engine and the above things should be working with the calculator but I think they go into separate classes I'm not too sure. I think this is the code required ( in order first is the calculator second is the engine for the calculator)

  import javax.swing.*; 
import java.awt.GridLayout; 
import java.awt.BorderLayout; 


public class NewCalculator { 
 // The below code is the basics for constructing buttons to be used in the program as you can see I have created all the buttons you would see in a regular calculator.
	JButton button0=new JButton("0"); 
	JButton button1=new JButton("1"); 
	JButton button2=new JButton("2"); 
	JButton button3=new JButton("3"); 
	JButton button4=new JButton("4"); 
	JButton button5=new JButton("5"); 
	JButton button6=new JButton("6"); 
	JButton button7=new JButton("7"); 
	JButton button8=new JButton("8"); 
	JButton button9=new JButton("9"); 
	 
	JButton buttonPoint = new JButton("."); 
	JButton buttonEqual=new JButton("="); 
	 
	JButton buttonPlus =new JButton("+"); 
	JButton buttonMinus =new JButton("-"); 
	JButton buttonDivide=new JButton("/"); 
	JButton buttonMultiply=new JButton("*"); 
	JButton buttonOox=new JButton("1/x");
	JButton buttonSqrt=new JButton("sq");
	JButton buttonPercentage=new JButton("&");
	JButton buttonClear=new JButton("C");
	
	JPanel windowContent = new JPanel(); 
	JTextField displayField = new JTextField(30); 
	
	NewCalculator(){ 
		BorderLayout bl = new BorderLayout(); 
		windowContent.setLayout(bl); 
		 windowContent.add("North",displayField); 
		 
		 JPanel p1 = new JPanel(); 
		 GridLayout gl =new GridLayout(4,3); 
		 p1.setLayout(gl); 
		  
		 p1.add(button1); 
		 p1.add(button2); 
		 p1.add(button3); 
		 p1.add(button4); 
		 p1.add(button5); 
		 p1.add(button6); 
		 p1.add(button7); 
		 p1.add(button8); 
		 p1.add(button9); 
		 p1.add(button0); 
		 p1.add(buttonPoint); 
		 p1.add(buttonEqual); 
		 windowContent.add("Center",p1); 
		 
		 JPanel p2 = new JPanel(); 
		 GridLayout gl2 =new 
		 GridLayout(4,2); 
		 p2.setLayout(gl2); 
		 p2.add(buttonPlus); 
		 p2.add(buttonMinus); 
		 p2.add(buttonMultiply); 
		 p2.add(buttonDivide);
		 p2.add(buttonSqrt);
		 p2.add(buttonOox);
		 p2.add(buttonPercentage);
		 p2.add(buttonClear);
		 windowContent.add("East",p2); 
		 JFrame frame = new JFrame("NewCalculator"); 
		 frame.setContentPane(windowContent); 
		 frame.pack(); 
		 frame.setVisible(true); 
		 
		 CalculatorEngine calcEngine = new CalculatorEngine(this); 
		 
		 button0.addActionListener(calcEngine); 
		 button1.addActionListener(calcEngine); 
		 button2.addActionListener(calcEngine); 
		 button3.addActionListener(calcEngine); 
		 button4.addActionListener(calcEngine); 
		 button5.addActionListener(calcEngine); 
		 button6.addActionListener(calcEngine); 
		 button7.addActionListener(calcEngine); 
		 button8.addActionListener(calcEngine); 
		 button9.addActionListener(calcEngine); 
		  
		 buttonPoint.addActionListener(calcEngine); 
		 buttonPlus.addActionListener(calcEngine); 
		 buttonMinus.addActionListener(calcEngine); 
		 buttonDivide.addActionListener(calcEngine); 
		 buttonMultiply.addActionListener(calcEngine); 
		 buttonEqual.addActionListener(calcEngine); 
		 
		 buttonSqrt.addActionListener(calcEngine);
		 buttonOox.addActionListener(calcEngine);
		 buttonPercentage.addActionListener(calcEngine);
		 buttonClear.addActionListener(calcEngine);
		 } 
		  
		 public static void main(String[] args) { 
		 // Instantiate the class Calculator 
		 NewCalculator calc = new NewCalculator(); 
		 } 
		 } 

then its the engine.

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener; 
import javax.swing.JOptionPane;
import javax.swing.JButton; 

 
 

public class CalculatorEngine implements ActionListener { 
 

	NewCalculator parent; //a reference to Calculator window 
	char selectedAction = ' '; // +, -, /, or * 
	 
	double currentResult =0; 
	 
	// Constructor stores the reference to the Calculator 
	// window in the member variable parent 
	CalculatorEngine(NewCalculator parent){ 
	 
	this.parent = parent; 
	} 
	 
	public void actionPerformed(ActionEvent e){ 
		
		JButton clickedButton = (JButton) e.getSource();
		String
		dispFieldText=parent.displayField.getText();
		
		double displayValue=0;
		
		if (!"".equals (dispFieldText)){
			try { 
				 displayValue= Double.parseDouble(dispFieldText); 
				} catch (NumberFormatException e1) { 
				 // TODO Auto-generated catch block 
					javax.swing.JOptionPane.showConfirmDialog(null, "Please enter a Number", "Wrong input", javax.swing.JOptionPane.PLAIN_MESSAGE); 
							return; 
 
				} 

		}
		
	 Object src = e.getSource ();
	 
	 if (src == parent.buttonPlus){
		 selectedAction = '+';
		 currentResult=displayValue;
		 parent.displayField.setText ("");
	 }
	 else if (src == parent.buttonMinus){
		 selectedAction = '-';
		 currentResult=displayValue;
		 parent.displayField.setText ("");
	 }
	 else if (src == parent.buttonDivide){
		 selectedAction = '/';
		 currentResult=displayValue;
		 parent.displayField.setText ("");
	 }
	 else if (src == parent.buttonMultiply){
		 selectedAction = '*';
		 currentResult=displayValue;
		 parent.displayField.setText ("");
		
		 
	 }
	 else if (src == parent.buttonEqual){
		
		 if (selectedAction=='+'){
			 currentResult+=displayValue;
			 parent.displayField.setText(""+currentResult);
		 }
	 }else if (selectedAction=='-'){
		 currentResult -=displayValue;
		 parent.displayField.setText(""+currentResult);
	 }
	 else if (selectedAction=='/'){
		 currentResult /=displayValue;
		 parent.displayField.setText(""+currentResult);
	 }
	 else if (selectedAction=='*'){
		 currentResult *=displayValue;
		 parent.displayField.setText(""+currentResult);
	 }

	 else{
		 String clickedButtonLabel=clickedButton.getText();
		 parent.displayField.setText(dispFieldText +clickedButtonLabel);
	 }
	 
		 
	 }
	






		
	} 
 
 

[cire]

You may have more luck on a forum where Java is topical.