public int  readInt() throws IOException  {

    do  {
      try  {
        stdErr.print("Enter integer:  ");
        stdErr.flush();
        return  Integer.parseInt(stdIn.readLine());
      }
      catch (NumberFormatException  nfe)  {
        stdErr.println(nfe.toString());
      }
    }  while (true);
  }

do  {
  try  {

    // get data

    if (data-within-range)  {
      break;
    }
    else  {
      stdErr.println(data-out-of-range-message);
    }
  }
  catch (ExceptionType1  et1)  {
    stdErr.println(et1.toString());
  }

  catch (ExceptionType2  et2)  {
    stdErr.println(et2.toString());
  }

  ...

  catch (ExceptionTypen  etn)  {
    stdErr.println(etn.toString());
  }
}  while (true);

import java.io.*;

/**
 * class DisplayTextFile
 *
 * This program prompts the user for a filename, reads in the filename, 
 * then reads and  displays the contents on the console
 *
 * @author  Terence Chan
 * @version  1.0
 */

class DisplayTextFile {

  private static BufferedReader  stdIn = new  
			BufferedReader(new  InputStreamReader(System.in));
  private static PrintWriter  stdOut = new  PrintWriter(System.out, true);
  private static PrintWriter  stdErr = new  PrintWriter(System.err, true);

  /**
   * prompt the user for a filename, read in the filename, open the file, 
   * then reads and  displays the contents on the console
   * @param args command line arguments
   * @throws IOException  If an input or output exception occurred
   */

   public static void main(String[] args) throws IOException {

     BufferedReader  inFile = null;

     // prompt the user for filename

     do  {
         try  {
		stdOut.print("Enter Filename : ");
		stdOut.flush();
	        inFile = new BufferedReader(new  FileReader(stdIn.readLine()));
	 } catch (FileNotFoundException  fnfe)  {
			        stdErr.println(fnfe.toString());
				break;
 	   }

 	// read and display contents

	String textLine;

	textLine=inFile.readLine();

	while (textLine!=null) {
		stdOut.println(textLine);
		textLine=inFile.readLine();
   	}

	inFile.close();

	break;

     }  while (true);
  }
}

import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import java.net.*;

public class ChoseSomeURL extends Applet implements 
                                      ItemListener {

  Choice siteURL;
  Label label;

  String site[] = {	"http://www.cityu.edu.hk/",
			"http://www.yahoo.com.hk/" };


  public void init() {
    label = new Label("URL");
    siteURL = new Choice();

    // add items to siteURL list
    for (int i = 0; i < site.length; i++)
	siteURL.add(site[i]);

    // add choice lists to window
    add(label);
    add(siteURL);
     
    // register to receive item events
    siteURL.addItemListener(this);
  }

  public void itemStateChanged(ItemEvent ie) {

    try {
    	URL url = new URL(siteURL.getSelectedItem());
    	getAppletContext().showDocument(url,"_blank");
    } catch(MalformedURLException mue) {}
   }
}

class SwapTwoIntWithValidation {
  public static void main(String[] args) {

    int temp, a = 0, b = 0;

    try {
        a = Integer.parseInt(args[0]);
        b = Integer.parseInt(args[1]);
    } catch (IndexOutOfBoundsException iobe) {
	      System.out.println(iobe.toString());
	      System.exit(0);
      }

    System.out.println("before swapping a and b  : " + a + " " + b);

    temp = a;
    a = b;
    b = temp;

    System.out.println("after swapping a and b  : " + a + " " + b);
  }
}

class QuadraticSolver {
 public static void main(String[] args) {

 int a, b, c;

 try {
     a = Integer.parseInt(args[0]);
     b = Integer.parseInt(args[1]);
     c = Integer.parseInt(args[2]);

     if ((a == 0) && (b == 0))
	throw new IllegalArgumentException("Invalid input: (a == 0) && (b == 0)");

     if (b*b < 4*a*c)
	throw new IllegalArgumentException("Invalid input: b*b < 4*a*c");

     if (a == 0)
        System.out.println("x = " + -c/b);
     else {
          System.out.println("x1 = " + ((-b + Math.sqrt(b*b-4*a*c))/(2*a)));
          System.out.println("x2 = " + ((-b - Math.sqrt(b*b-4*a*c))/(2*a)));
     }

 } catch (IndexOutOfBoundsException iobe) {
      System.out.println(iobe.toString());
   }
   catch (NumberFormatException nfe) {
      System.out.println(nfe.toString());
   }
   catch (IllegalArgumentException iae) {
      System.out.println(iae.toString());
   }
   catch (ArithmeticException ae) {
      System.out.println(ae.toString());
   }
 }
}