Comparison methods

[sjalle]

But, since you posted it here I couldn't resist adding/tweaking it a bit

Among the useless things I did was renaming getC and GetF, mostly
because getC rings like an age old io function to me...

import java.util.*;
import java.text.*;
/**
 * A sortable, formatted and printable temperature class
 *
 */
public class Temperature implements Comparator   { //Class name
  /**
   * format for printing temperature values
   */
  static DecimalFormat df=new DecimalFormat("0.0");
  double temp; //Variable

  char scale; //Varible

  public Temperature() { //Default Constructor
    temp = 0;
    scale = 'C';
  }

  public Temperature(char tempScale) { //Scale Constructor
    temp = 0;
    scale = tempScale;
  }

  public Temperature(double tempValue) { //Temp Constructor
    temp = tempValue;
    scale = 'C';
  }

  public Temperature(double tempValue, char tempScale) { //Constructor
    temp = tempValue;
    scale = tempScale;
  }

  public double getCelsius() { //Used to get degrees C
    double value;
    if (scale == 'C') {
      return temp;
    }
    else {
      return ( (double) (Math.round( (5 * (temp - 32.0) / 9.0) * 10.0)) / 10);
    }
  }

  public double getFarenheit() { //Used to get degrees F
    if (scale == 'F') {
      return temp;
    }
    else {
      return (Math.round( (9 * (temp / 5) + 32) * 10) / 10);
    }
  }

  public void setTemp(double newTemp) { //set temp
    temp = newTemp;
  }

  public void setScale(char newScale) { //set scale
    scale = newScale;
  }

  public void setTempScale(double newTemp, char newScale) { //set both
    temp = newTemp;
    scale = newScale;
  }
  /**
   * return a formatted temperature string
   * @return
   */
  public String toString () {
    return df.format(temp)+" "+scale;
  }
  /**
   * the equals method should be implemented as an override of the
   * Object class' equals method, parameter should be an Object.
   * Note: the two next metods define the Comparator interface
   * Among othjer things this enables sorting.
   * @param obj
   * @return
   */
  public boolean equals(Object obj) { //compares for equality
    if (!(obj instanceof Temperature)) {
      return false;
    }
    Temperature aTemp=(Temperature)obj;
    return (getCelsius() == aTemp.getCelsius());
  }
  /**
   * Method used by  Collections.sort
   * @param o1
   * @param o2
   * @return
   */
  public int compare(Object o1, Object o2) {
    Temperature t1=(Temperature)o1;
    Temperature t2=(Temperature)o2;
    // switch t1 & t2 here to get descending sort
    return (int)(t1.getCelsius()*10.0d-t2.getCelsius()*10.0d);
  }
  // This is comparing statements to see if the first is greater than the second
  public boolean greaterThan(Temperature obj) {
    return (getCelsius() > obj.getCelsius());
  }

  // This is comparing  statements to see if the first is less than the second
  public boolean lessThan(Temperature obj) {
    return (getCelsius() < obj.getCelsius());
  }

  // Returns temp value
  public double getTemperatureTemp() {
    return temp;
  }

  // Returns scale character
  public char getTemperatureScale() {
    return scale;
  }

  public static void main(String[] args) {
    Temperature t = new Temperature(100.5, 'C');
    System.out.println("\n\nt:"+t);
    // stuff an arrayList with temperatures and sort them on actual heat value
    ArrayList tList=new ArrayList();
    tList.add(t);
    tList.add(new Temperature(140.5,'F'));
    tList.add(new Temperature(60,'C'));
    tList.add(new Temperature(90,'F'));
    tList.add(new Temperature(70.3,'C'));
    tList.add(new Temperature(.7,'C'));
    // the 'new Temperature()' parameter here is just a dummy for using the
    // Temperature class' Comparator
    Collections.sort(tList,new Temperature());
    System.out.println("Sorted temperatures");
    for (int i=0; i<tList.size(); i++) {
      System.out.println(tList.get(i));
    }
  }
}

[javajo]

Cool! Thanks for your response.

The outcome is not exactly what the assignment calls for.

Recap of Assignment:
Then write a driver program that tests all the methods. Be sure to use each of the constructors, to include at least one true and one false case for each of the comparison methods, and to test at least the following temperature equalities: 0.0 degrees Celsius = 32.0 degrees Fahrenheit, -40.0 degrees Celsius= -40.0 degrees Fahrenheit, and 100.0 degrees Celsius = 212.0 degrees Fahrenheit.

Below is incomplete code for my driver program. I am not sure which methods to invoke to test the temperatures for equality, greater than or less than.
Can you help?

 public class TemperatureDemo
 {
     public static void main (String[] args)
     {
        //Instantiate temp object
        Temperature temp = new Temperature();

        //invoke methods
        temp.getCelsius();
        temp.getFarenheit();

        System.out.println("Testing Temperature Class");

        System.out.print("0.0 degrees C is ");
        //what method will determine = to, > than or < than ???
        System.out.print("(equal to, greater than or less than)");
        System.out.println(" 32.0 degrees F");

        System.out.print("-40.0 degrees C is ");
        //what method will determine = to, > than or < than ???
        System.out.print("(equal to, greater than or less than)");
        System.out.println(" -40.0 degrees F");

        System.out.print("100.0 degrees C is ");
        //what method will determine = to, > than or < than ???
        System.out.print("(equal to, greater than or less than)");
        System.out.println(" 212.0 degrees F");
     {

    }
  }
} 

[javajo]

My final is tomorrow and I still have another assignment to complete. I know that's not your problem, just looking for some help with this TemperatureDemo. A few hints would help.

I think I have to invoke the following methods to get the result the assignment calls for:

 // This is comparing statements to see if the first is greater than the second
  public boolean greaterThan(Temperature obj) {
    return (getCelsius() > obj.getCelsius());
  }

  // This is comparing  statements to see if the first is less than the second
  public boolean lessThan(Temperature obj) {
    return (getCelsius() < obj.getCelsius());
  }

  // Returns temp value
  public double getTemperatureTemp() {
    return temp;
  }

  // Returns scale character
  public char getTemperatureScale() {
    return scale;
  } 

Am I close?
Thanks,
~Jo

[javajo]

I found the Driver Template. I'm going to try to figure it out.

public class TempDriver
{
   ...

   Temperature t1=new Temperature();
   Temperature t2=new Temperature(32.0);
   Temperature t3=new Temperature('C');
   Temperature t4=new Temperature(75.5, 'F');


   if (t1.equals(t2))
      System.out.println("Temperature 1 is equal to temperature 2.");
   else
      System.out.println("Temperature 1 is not equal to temperature 2."); 

[javajo]

I have modified this program from a simple "adding machine" and changed it to perform subtraction, multiplication & division however I have not studied any mathematical equations yet. Does anyone know how to make the Subtract, Multiply & Divide buttons work properly on this application?

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

/**
 GUI for adding, subtractin, multiplying and dividing
 a series of numbers.
*/
public class Calculator extends JFrame implements ActionListener
{
    public static final int WIDTH = 400;
    public static final int HEIGHT = 200;

    private JTextField inputOutputField;
    private double sum = 0;
    private double difference = 0;
    private double product = 0;
    private double quotient = 0;

    public static void main(String[] args)
    {
        Calculator guiCalculator = new Calculator( );
        guiCalculator.setVisible(true);
    }

    public Calculator( )
    {
        setTitle("Simple Calculator");
        addWindowListener(new WindowDestroyer( ));
        setSize(WIDTH, HEIGHT);
        Container contentPane = getContentPane( );
        contentPane.setLayout(new BorderLayout( ));

        JPanel buttonPanel = new JPanel( );
        buttonPanel.setBackground(Color.GRAY);
        buttonPanel.setLayout(new FlowLayout( ));
        JButton addButton = new JButton("Add");
        addButton.addActionListener(this);
        buttonPanel.add(addButton);
        JButton subtractButton = new JButton("Subtract");
        subtractButton.addActionListener(this);
        buttonPanel.add(subtractButton);
        JButton multiplyButton = new JButton("Multiply");
        multiplyButton.addActionListener(this);
        buttonPanel.add(multiplyButton);
        JButton divideButton = new JButton("Divide");
        divideButton.addActionListener(this);
        buttonPanel.add(divideButton);
        JButton resetButton = new JButton("Reset");
        resetButton.addActionListener(this);
        buttonPanel.add(resetButton);
        contentPane.add(buttonPanel, BorderLayout.SOUTH);

        JPanel textPanel = new JPanel( );
        textPanel.setBackground(Color.BLUE);
        textPanel.setLayout(new FlowLayout( ));

        inputOutputField = new JTextField("Numbers go here.", 30);
        inputOutputField.setBackground(Color.WHITE);
        textPanel.add(inputOutputField);
        contentPane.add(textPanel, BorderLayout.CENTER);
    }

    public void actionPerformed(ActionEvent e)
    {
        if (e.getActionCommand( ).equals("Add"))
        {
            sum = sum +
                stringToDouble(inputOutputField.getText( ));
            inputOutputField.setText(Double.toString(sum));
        }
        else if (e.getActionCommand( ).equals("Subtract"))
        {
                 difference =
                 stringToDouble(inputOutputField.getText());
                 inputOutputField.setText(Double.toString(difference));
        }
        else if (e.getActionCommand( ).equals("Multiply"))
        {
                    product =
                        stringToDouble(inputOutputField.getText( ));
                    inputOutputField.setText(Double.toString(product));
        }
        else if (e.getActionCommand( ).equals("Divide"))
        {
                    quotient =
                        stringToDouble(inputOutputField.getText( ));
                    inputOutputField.setText(Double.toString(quotient));
        }
        else if (e.getActionCommand( ).equals("Reset"))
        {
            sum = 0;
            inputOutputField.setText("0.0");
        }
        else
            inputOutputField.setText("Error in adder code.");
     }

    private static double stringToDouble(String stringObject)
    {
        return Double.parseDouble(stringObject.trim( ));
    }
}