error message window and ceasing execution

Is there a way to do a message window?  I am doing a project for my class and thought I would go above and beyond.  I would like to put in some error checking so if my value is less than 1 or greater than 99 I'd like to pop a window and cease executiong.  Is this possible?

package project2;

import java.awt.*;
import java.awt.event.*;

import javax.swing.*;


public class ChangeWindow implements ActionListener  
{
      JFrame coinFrame;
    JPanel coinPanel,textPanel;
    JTextField amount,txtAmount;
    JLabel amountLabel;
    DisplayCoins coinWindow;
    JButton enterAmount;
    Graphics2D graphics;
    int quarters,dimes,nickels,pennies;
    int intCoins;
    String number;
   
      public void ChangeWIndow()
      {
      
            quarters= 0;
            dimes=0;
            nickels=0;
            pennies=0;
            
      }
      
      public void SetChange()
      {
                  
              // Create my window and set up the title
              coinFrame = new JFrame("Enter value between 1 and 99");
              coinFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
              coinFrame.setSize(new Dimension(700, 700));
              
              // Create the coin panel
              coinPanel = new JPanel(new GridLayout(10, 10));
              textPanel = new JPanel(new GridLayout(10, 10));
              coinWindow = new DisplayCoins();
              
              //Adds the widgets to the panel
              addWidgets();
                           
              //Set the default button.
              coinFrame.getRootPane().setDefaultButton(enterAmount);
              
              //Add the panel to the window.
              coinFrame.getContentPane().add(coinPanel, BorderLayout.NORTH);
              coinFrame.getContentPane().add(coinWindow, BorderLayout.CENTER);
              coinFrame.getContentPane().add(textPanel, BorderLayout.SOUTH);

              //Display the window.
              coinFrame.pack();
              coinFrame.setVisible(true);
              
                    
      }
      
      // method to add widgets to the panel
       private void addWidgets() {
              //Create widgets.
              amount = new JTextField(2);
              amountLabel = new JLabel("Amount of change between 1 and 99", SwingConstants.HORIZONTAL);
              enterAmount = new JButton("Click to enter value");
              txtAmount = new JTextField(50);

              //Listen to events from the click button.
              enterAmount.addActionListener(this);

              //Add the widgets to the container.
              coinPanel.add(amount);
              coinPanel.add(amountLabel);
              coinPanel.add(enterAmount);
              textPanel.add(txtAmount);
              
              amountLabel.setBorder(BorderFactory.createEmptyBorder(5,5,5,5));
              
          }
    //       Change number value to words
      private void setAmountString(int amount)
      {
            
            String[] numbers = {"zero","One","Two","Three","Four","Five","Six","Seven","Eight","Nine","Ten","Eleven",
                        "Twelve","Thirteen","Fourteen","Fifteen","Sixteen","Seventeen","Eighteen","Nineteen"};
                        
            if (amount > 1 && amount <20)
            {
                  number = numbers[amount];            
            }
            else if (amount >19 && amount <30 )
            {                                    
                  number = "Twenty "+numbers[amount-20]+" Cents";                  
            }
            else if (amount >29 && amount <40 )
            {                                    
                  number = "Thirty "+numbers[amount-30]+" Cents";                  
            }
            else if (amount >39 && amount <50 )
            {                                    
                  number = "Fourty "+numbers[amount-40]+" Cents";                  
            }
            else if (amount >49 && amount <60 )
            {                                    
                  number = "Fifty "+numbers[amount-50]+" Cents";                  
            }
            else if (amount >59 && amount <70 )
            {                                    
                  number = "Sixty "+numbers[amount-60]+" Cents";                  
            }
            else if (amount >69 && amount <80 )
            {                                    
                  number = "Seventy "+numbers[amount-70]+" Cents";                        
            }
            else if (amount >79 && amount <90 )
            {                                    
                  number = "Eighty "+numbers[amount-80]+" Cents";                  
            }
            else if (amount >89 && amount <100 )
            {                                    
                  number = "Ninety "+numbers[amount-90]+" Cents";                  
            }
            
            
      }
      
      //Actions performed after you click the button
      public void actionPerformed(ActionEvent event)
      {
            //sets the number of quarters nickles dimes and pennies
            String value= amount.getText();
        intCoins = Integer.parseInt(value);
       
       
        //Determines the number of each coin
            quarters = intCoins/25;
        int tempValue = intCoins%25;
        dimes = tempValue/10;
        tempValue = tempValue%10;
        nickels = tempValue/5;
        tempValue= tempValue%5;
        pennies = tempValue;
       
       
       
        //turns the number into a string
        setAmountString(intCoins);
        txtAmount.setText(this.number);
        //Testing to check string
       
        graphics = (Graphics2D) coinFrame.getGraphics();
            
        //coinWindow.paintComponent(graphics);
        coinWindow.
       
       
      }
      
      public class DisplayCoins extends JPanel
      {
            /**
             *
             */
            private static final long serialVersionUID = 1L;
            
            
            
            public void paintComponent(Graphics2D graphics)
            {
                  
                  
              paintQuarters(quarters);             
              paintDimes(dimes);
              paintNickels(nickels);
              paintPennies(pennies);                                
            }
            private void paintQuarters(int quarters)
            {
                  int y =190;
                  int x = 50;
                  for (int i=1; i<=quarters;i++)
                  {
                        Coins c = Coins.QUARTER;
                        c.paint(graphics,y,x);
                        y=y+10;
                  }
                  
            }
            
            private void paintDimes(int dimes)
            {
                  int y =190;
                  int x=150 ;
                  
                  for (int i=1; i<=dimes;i++)
                  {
                        Coins c = Coins.DIME;
                        c.paint(graphics,y,x);
                        y=y+10;
                  }
            }
            private void paintNickels(int nickels)
            {
                  int y =190;
                  int x=225;
                  for (int i=1; i<=nickels;i++)
                  {
                        Coins c = Coins.NICKEL;
                        c.paint(graphics,y,x);
                        y=y+10;
                  }
            }
            private void paintPennies(int pennies)
            {
                  int y =190;
                  int x=310;
                  
                  for (int i=1; i<=pennies;i++)
                  {
                        Coins c = Coins.PENNY;
                        c.paint(graphics,y,x);
                        y=y+10;
                  }
            }
      }
      
}
---------------------------------------------------------------------------
package project2;

import java.awt.*;

public enum Coins {

      QUARTER("25",75,Color.lightGray),DIME("10",55,Color.lightGray),
      NICKEL("5",65,Color.lightGray.darker()),PENNY("1",60,Color.orange.darker());
      
      private Color color;
      private String value;
      private int size;
      
      private Coins (String value, int size,Color color)
      {
            this.color = color;
            this.value = value;
            this.size = size;
      }
      public int getSize()
      {
            return this.size;
      }
      
      public String getValue()
      {
            return this.value;
      }
      
      public Color getColor()
      {
            return this.color;
      }
      public void paint(Graphics2D g, int y, int x)
    {
            g.setStroke(new BasicStroke(6.0f));
        g.setColor(Color.black);
        g.drawOval(x, y, size, size);
        g.setColor(color);
        g.fillOval(x, y, size-2, size-2);
        g.setColor(Color.black);
        g.drawString(this.value, x+(this.getSize()/2)-8, y+(this.getSize()/2)+2);
   }
}