CSCI 146: Lab 1 Materials

The main goal of Lab 1 is to introduce Emacs as a simple program development environment, and Java compiler that comes with SDK 2 (JDK 1.3). A secondary goal is to learn how to use a web browser to download programs from the world-wide web. The following activities will be carried out:

• How to access Emacs and Java.
• How to write, save, compile, build, and execute the ``Hello, world!'' program in Java.
• How to write, etc. a "Write Hello" program, by completing the given code snippet. (Optional; not graded.)
• How to download a program from the world-wide web: The temperature conversion program from Chapter 1 of the textbook.
• Alternative download site.
• Documentation conventions: Javadoc, pre- and post-conditions.

  Here is the ``Hello, world!'' program in Java:
  

  // FILE: hello.java
  // The ``Hello, world!'' program in Java 
  // Precondition: None
  // Postcondition: Hello, world! is printed to standard output.
  
  public class MyHello
  {
      public static void main(String[] args)
      {
          System.out.println("Hello world");
      }
  }
  
  

  // FILE: second.java
  public class second
  {
  private String s="My Hello to You All!";
  ....
  public second()
  {
  ....
  }
  // The ``My Hello to You All!'' method in Java 
  // Precondition: None
  // Postcondition: My Hello to You All! is printed to standard output.
  public static void main(String args[])
  {
  ....
  ....
  ....
  }
  }
  

  
  // File: TemperatureConversion.java
  // A Java application to print a temperature conversion table.
  // Additional javadoc documentation is available at:
  //   http://www.cs.colorado.edu/~main/docs/TemperatureConversion.html
  
  import java.text.NumberFormat; // Used in the printNumber method.
  
  /******************************************************************************
  * The TemperatureConversion Java application prints a table 
  * converting Celsius to Fahrenheit degrees.
  *
  * 
  Java Source Code for this class:
  
  *   
  *   http://www.cs.colorado.edu/~main/applications/TemperatureConversion.java
  *   
  *
  * @author Michael Main 
  *    (main@colorado.edu) 
  *
  * @version
  *   Feb 22, 1999
  ******************************************************************************/
  public class TemperatureConversion 
  {
  
     /**
     * The main method prints a Celsius to Fahrenheit conversion
     * table.
     * The bounds of the table range from -50C to +50C in 10 degree increments.
     * The String argumments (args) are not used
     * in this implementation.
     **/
     public static void main(String[ ] args) 
     {
        final double TABLE_BEGIN = -50.0; // The table's first Celsius temperature
        final double TABLE_END   =  50.0; // The table's final Celsius temperature
        final double TABLE_STEP  =  10.0; // Increment between temperatures in table
        final int    WIDTH       =     6; // Number of characters in output numbers
        final int    ACCURACY    =     2; // Number of digits to right of decimal pt
               
        double celsius;                   // A Celsius temperature
        double fahrenheit;                // The equivalent Fahrenheit temperature
  
        System.out.println("TEMPERATURE CONVERSION");
        System.out.println("----------------------"); 
        System.out.println("Celsius     Fahrenheit");
         
        for (celsius = TABLE_BEGIN; celsius <= TABLE_END; celsius += TABLE_STEP) 
        {  // Each iteration prints one line of the conversion table.
           fahrenheit = celsiusToFahrenheit(celsius);
           printNumber(celsius, WIDTH, ACCURACY);                               
           System.out.print("C        ");
           printNumber(fahrenheit, WIDTH, ACCURACY);
           System.out.println("F");
        }
        System.out.println("----------------------");
     }
   
          
     /**
     * Convert a temperature from Celsius degrees to Fahrenheit degrees.
     * @param c 
     *   a temperature in Celsius degrees
     * 
  Precondition:
  
     *   c >= -273.16.
     * @return 
     *   the temperature c converted to Fahrenheit
     * @exception java.lang.IllegalArgumentException
     *   Indicates that c is less than the smallest Celsius 
     *   temperature (-273.16).
     **/
     public static double celsiusToFahrenheit(double c)
     {
        final double MINIMUM_CELCIUS = -273.16;
  
        if (c < MINIMUM_CELCIUS)
           throw new IllegalArgumentException("Argument " + c + " is too small.");
        return (9.0/5.0)*c + 32;
     }
  
        
     /**
     * Print a number to System.out, using a specified format.
     * @param d
     *   the number to be printed
     * @param minimumWidth
     *   the minimum number of characters in the entire output
     * @param fractionDigits
     *   the number of digits to print on the right side of the decimal point
     * 
  Precondition:
  
     *   fractionDigits is not negative.
     * 
  Postcondition:
  
     *   The number d has been printed to System.out.
     *   This printed number is rounded to the specified number of digits on the
     *   right of the decimal. If fractionDigits is 0,
     *   then only the integer part of d is printed.
     *   If necessary, spaces appear at the front of the number to raise
     *   the total number of printed characters to the minimum. Additional
     *   formatting details are obtained from the current locale. For example,
     *   in the United States, a period is used for the decimal and commas are
     *   used to separate groups of integer digits.
     * @exception java.lang.IllegalArgumentException
     *   Indicates that fractionDigits is negative.
     * 
  Example:
  
     *   printNumber(12345.27, 8, 1); // Prints 12,345.3 in the U.S. 
     **/  
     public static void printNumber(double d, int minimumWidth, int fractionDigits)
     {
        // Note: getNumberInstance( ) creates a NumberFormat object using
        // local information about the characters for a decimal point and
        // separators.
        NumberFormat form = NumberFormat.getNumberInstance( );
        String output;
        int i;
        int length;
  
        // Set the number of digits to appear on the right of the decimal.
        if (fractionDigits < 0)
           throw new IllegalArgumentException("fractionDigits < 0:" + fractionDigits);
        form.setMinimumFractionDigits(fractionDigits);
        form.setMaximumFractionDigits(fractionDigits);
          
        // Round and format the number. Note that form.format does correctly
        // rounds a number. Also note that setting fractionDigits to zero
        // doesn't seem to work (it still prints a decimal point and one digit).
        // So I have extra code to handle that situation.
        output = form.format(d);
        length = output.length( );
        if (fractionDigits == 0 && length > 1 && output.charAt(length-2) == '.')
           output = "  " + output.substring(0,length-2);
  
        // Print any leading spaces and the number itself.
        for (i = minimumWidth-length; i > 0; i--)
  	   System.out.print(' ');
        System.out.print(output);
     }
           
  }