1. ./Chicken.java
2. ./Farm2.java
3. ./Farm.java
4. ./ParameterPassingDemo1.java
5. ./ParameterPassingDemo2.java

import java.util.Scanner;

/**
 * A Java class that represents a chicken. The state of the chicken is
 * its name, height and weight.  There is also a static variable
 * representing the name of the farm that the Chickens are on.
 * 
 * Added static methods
 *
 * Run program with the argument "test" to test the class.
 * 
 * @author Sara Sprenkle
 */
public class Chicken {

    // ------------ INSTANCE VARIABLES -------------------

    /** the name of the chicken */
    private String name;

    /** the height of the chicken in centimeters */
    private int height;

    /** the weight of the chicken in pounds */
    private double weight;


    // ------------ CLASS VARIABLES ------------------

    /** the name of the farm the chickens are on */
    private static final String FARM = "McDonald";

    /** the amount of weight the chicken gains during feeding */
    private static double WEIGHT_GAIN = .3;

    /** the amount of height the chicken gains during feeding */
    private static int HEIGHT_GAIN = 1;
    
    /** the amount of weight difference we are okay with */
    public static final double ERROR_TOLERANCE = .0001;


    /**
     * Create a new Chicken object with the charactistics as specified by the
     * parameters.
     * @param name the name of the chicken
     * @param height the height of the chicken in centimeters
     * @param weight the weight of the chicken in pounds
     */
    public Chicken(String name, int height, double weight) {
        this.name = name;
        this.height = height;
        this.weight = weight;
    }

    /**
     * Default name: "Bubba"; height and weight specified by parameters
     * @param height the height of the chicken in centimeters
     * @param weight the weight of the chicken in pounds
     */
    public Chicken(int height, double weight) {
        // if the user doesn't specify a name, let's make it Bubba
        this("Bubba", height, weight);
    }

    //
    // ----------- GETTER METHODS ------------
    // (also Accessor methods)

    /**
     * Returns the chicken's height, in centimeters
     * 
     * @return the height of the chicken, in centimeters
     */
    public int getHeight() {
        return this.height;
    }

    /**
     * Returns the chicken's weight, in pounds
     * 
     * @return the weight of the chicken, in pounds
     */
    public double getWeight() {
        return weight;
    }

    /**
     * Returns the chicken's name
     *
     * @return the name of the chicken
     */
    public String getName() {
        return name;
    }

    //
    // ------------- MUTATORS -----------
    //

    /**
     * Feeds the chicken, increasing the chicken's weight and height
     */
    public void feed() {
        weight += WEIGHT_GAIN;
        height += HEIGHT_GAIN;
    }

    //
    // ------------- SETTERS ----------
    //

    /**
     * Sets the name of the chicken
     * 
     * @param n the name of the chicken
     */
    public void setName(String n) {
        name = n;
    }

    /**
     * Sets the height of the chicken, in cm
     * 
     * @param h the height of the chicken, in cm
     */
    public void setHeight(int h) {
        height = h;
    }

    /**
     * Sets the weight of the chicken, in pounds
     * 
     * @param w the weight of the chicken, in pounds
     */
    public void setWeight(double w) {
        weight = w;
    }

    /**
     * Returns a string representation of the chicken.
     * Format:
     * <br/>Chicken name: &lt;name&gt;
     * <br/>weight: &lt;weight&gt; pounds
     * <br/>height: &lt;height&gt; cm
     * <p>Weight is displayed to one decimal place
     * @return a string representation of this Chicken
     */
    @Override
    public String toString() {
        // Use a StringBuilder: more efficient than concatenating strings.
        StringBuilder rep = new StringBuilder("Chicken name: ");
        rep.append(name);
        rep.append("\nweight: ");
        rep.append(String.format("%.1f", weight)); // guesses as to what this does?
        rep.append(" pounds");
        rep.append("\nheight: ");
        rep.append(height);
        rep.append(" cm");
        return rep.toString();
    }

    /**
     * Determines if the Object o is equivalent to this Chicken, 
     * based on their name, height, and weight.
     * @param o the object to compare
     * @return true if this object is the same as the o argument (by name, height, and wight).  Otherwise, returns false. 
     */
    @Override
    public boolean equals(Object o) {
        // Follows the _Effective Java_ process
        if( o == this ) {
            return true;
        }

        if( ! ( o instanceof Chicken ) ) {
            return false;
        }

        Chicken other = (Chicken) o;

        if( ! other.getName().equals(this.getName() ) ) {
            return false;
        }

        if( other.getHeight() != this.getHeight() ) {
            return false;
        }

        if( Double.compare( other.getWeight(), this.getWeight()) == 0 ) {
            return true;
        }

        // if the weight is close enough, let's consider them
        // equivalent
        double difference = this.getWeight() - this.getWeight();
        if( difference > ERROR_TOLERANCE ) {
            return false;   
        }

        return true;

    }
    
    /**
     * This method tests the class.
     */
    private static void test() {
        int fredHeight = 38;
        Chicken chicken = new Chicken("Fred", fredHeight, 2.0);

        System.out.println(chicken);

        if( chicken.getHeight() != fredHeight ) {
            System.err.println("Problem likely in constructor setting height");
        }
        if( !chicken.getName().equals("Fred") ) {
            System.err.println("Problem likely in constructor setting name");
        }

        chicken.feed();

        int newFredHeight = chicken.getHeight();

        System.out.println();
        System.out.println(chicken.getName() + " is now " + newFredHeight +
                           " cm tall.");

        chicken.feed();

        System.out.println("He's a growing boy at " + chicken.getHeight() + " cm tall and " + chicken.getWeight() + " pounds");

        System.out.println("\nLook at this beautiful formatting: ");
        System.out.println(chicken);

        String expectedRep = "Chicken name: Fred\nweight: 2.6 pounds\nheight: 40 cm";
        String actualRep = chicken.toString();

        // Test the toString method
        if( ! actualRep.equals(expectedRep) ) {
            System.err.println("Problem in toString");
            System.err.println("\tActual: " + actualRep);
            System.err.println("\tExpected: " + expectedRep);
        }

        Chicken trivialMatch = chicken;

        // Test equals method
        if( ! chicken.equals(trivialMatch) ) {
            System.err.println("Problem in equals");
            System.err.println("\tActual: " + chicken.equals(trivialMatch) );
            System.err.println("\tExpected: " + true);
        }

        Chicken grownFred = new Chicken("Fred", 40, 2.6);
        // Works because we have some error tolerance in weight comparison
        if( ! chicken.equals(grownFred) ) {
            System.err.println("Problem in equals");
            System.err.println("\tActual: " + chicken.equals(grownFred) );
            System.err.println("\tExpected: " + true);
        }

        // TODO: more testing of equals method.  Only tested true
        // cases.


        // ---- creating tests for chickens -----

        String[] names = {"Rocky", "Baby Chicken"};
        double[] weights = {4.0, .8};
        int[] heights = {50, 4};
        String[] newNames = {"Rocky II", "Chicken"};

        for( int i=0; i < names.length; i++ ) {
            Chicken thisChicken = new Chicken( names[i], heights[i], weights[i] );

            if( !thisChicken.getName().equals(names[i]) ) {
                System.err.println("Problem likely in constructor setting name");
                System.err.println("\tActual: " + thisChicken.getName());
                System.err.println("\tExpected: " + names[i]);
            }


            if( thisChicken.getWeight() != weights[i] ) {
                System.err.println("\tError in getWeight for Chicken " + i );
                System.err.println("\tActual: " + thisChicken.getWeight());
                System.err.println("\tExpected: " + weights[i] );
            }

            // feed the chicken and check the state
            thisChicken.feed();
            if( thisChicken.getWeight() != weights[i] + WEIGHT_GAIN ) {
                System.err.println("Error in feed weight for Chicken " + i);
                System.err.println("\tActual: " + thisChicken.getWeight());
                System.err.println("\tExpected: " + (weights[i] + WEIGHT_GAIN) );
            }

            if( thisChicken.getHeight() != heights[i] + HEIGHT_GAIN ) {
                System.err.println("Error in feed height for Chicken " + i);
                System.err.println("\tActual: " + thisChicken.getHeight());
                System.err.println("\tExpected: " + (heights[i] + HEIGHT_GAIN) );
            }

            // feed the chicken again and check the state

            thisChicken.feed();

            // NOTE: this test may fail, but tried to address by giving some
            // error tolerance on the weight
            double expectedWeight2 = weights[i] + 2 * WEIGHT_GAIN;
            int comparison = Double.compare(thisChicken.getWeight(),  expectedWeight2 );
            if( comparison != 0 ) {
                if( thisChicken.getWeight() - expectedWeight2 > ERROR_TOLERANCE ) {
                    System.err.println("Error in second feed weight for Chicken " + i);
                    System.err.println("\tActual: " + thisChicken.getWeight());
                    System.err.println("\tExpected: " + (expectedWeight2 ));
                }
            }

            if( thisChicken.getHeight() != heights[i] + 2 * HEIGHT_GAIN ) {
                System.err.println("Error in second feed height for Chicken " + i);
                System.err.println("\tActual: " + thisChicken.getHeight());
                System.err.println("\tExpected: " + (heights[i] + 2 * HEIGHT_GAIN ));
            }
            
            thisChicken.setName(newNames[i]);
            
            if( !thisChicken.getName().equals(newNames[i]) ) {
                System.err.println("Problem likely in setName");
                System.err.println("\tActual: " + thisChicken.getName());
                System.err.println("\tExpected: " + newNames[i]);
            }

        }   
        
    }

    /**
     * Return the name of the Chickens' farm
     * @return the name of the Chickens' farm
     */
    public static String getFarm() {
        return FARM;   
    }
    
    /**
     * Feeds the given chicken the requested number of times.
     * @param chicken the chicken to feed
     * @param numTimes the number of times to feed the chicken
     */
     public static void feedChicken(Chicken chicken, int numTimes) {
         for(int i=0; i < numTimes; i++ ) {
            chicken.feed();   
         }
     }
     
     /**
      * Prompt the user for the chicken's characteristics.
      * Create and return a Chicken that has those characteristics.
      * @param scanner the Scanner from which to yet the user input.
      * @return the Chicken object that has the characteristics the
      *  user requested
      */
     public static Chicken createChickenWithUser(Scanner scanner) {
        System.out.print("What is the name of your chicken? ");
        String name = scanner.nextLine();
        
        System.out.print("What is the height of your chicken? ");
        int height = scanner.nextInt();
        
        System.out.print("What is the weight of your chicken? ");
        double weight = scanner.nextDouble();
        
        // get the last new line character from the double, 
        // don't do anything with it.
        scanner.nextLine();
        
        return new Chicken(name, height, weight);
     }
    
    /**
     * Runs the Chicken class. 
     * If the first command-line argument is "test", runs a test. 
     * Otherwise, there is a fun chicken feeding game.
     * 
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        
        if( args.length > 0 ) {
            if( args[0].equals("test") ) {
                test(); 
                System.exit(0);
            }
        }
        
        Scanner scanner = new Scanner(System.in);
        scanner.useDelimiter("\n");
        
        Chicken yourChicken = createChickenWithUser(scanner);
        System.out.println("Here's your chicken! " + yourChicken);

	// Refactor below code into a new static void method called
	// userFeedChicken
        
        System.out.print("Do you want to feed your chicken? (Y/N) ");
        String answer = scanner.nextLine();
        while( answer.equalsIgnoreCase("Y") ) {
            System.out.print("How many times do you want to feed the chicken? (1-3) ");
            int numTimes = scanner.nextInt();
            feedChicken(yourChicken, numTimes);
            
            scanner.nextLine(); // again, clear out the \n
            
            System.out.println("Here's your chicken! " + yourChicken);

            System.out.print("Do you want to feed your chicken again? (Y/N) ");
            answer = scanner.nextLine();
        }
        
        System.out.println("See you later!");
        
        scanner.close();

    }
}

/**
 * Represents a Farm (poorly).  
 * Primarly used to demonstrate pass by value for object variables
 * @author CSCI209
 */
public class Farm2 {

    private String name;

    public Farm2(String name) {
        this.name = name;
    }

    /**
     * c copies the value of the variable passed into the method.
     * When c is then assigned to a _new_ Chicken object, c now refers to 
     * a new address.  The original variable passed in does not change,
     * so updates to the new Chicken object do not affect the original 
     * Chicken object passed in.
     */
    public void feedChicken(Chicken c) {
        c = new Chicken(c.getName(), 
                        c.getHeight(), c.getWeight() );
        c.setWeight( c.getWeight() + .5);
    }

    public static void main(String[] args) {
        Farm2 farm = new Farm2("OldMac");
        Chicken sal = new Chicken("Sallie Mae", 45, 5.0);
        System.out.println(sal.getWeight());
        farm.feedChicken(sal);
        // sal is not affected
        System.out.println(sal.getWeight());
    }

}

/**
 * Represents a Farm (poorly).  
 * Primarly used to demonstrate pass by value for object variables
 * @author CSCI209
 */
public class Farm {

    private String name;

    public Farm(String name) {
        this.name = name;
    }

    /**
     * c copies the value of the variable passed into the method
     * so the Chicken object that is referenced by c will be
     * changed after this method returns.
     */
    public void feedChicken(Chicken c) {
        c.setWeight( c.getWeight() + .5 );
    }

    public static void main(String[] args) {
        Farm farm = new Farm("OldMac");
        Chicken sal = new Chicken("Sallie Mae", 45, 5.0);
        System.out.println(sal.getWeight());
        farm.feedChicken(sal);
        // weight of Sal will be higher.
        System.out.println(sal.getWeight());
    }

}

/**
 * Demonstrating Pass By Value with a primitive type.
 * Trace through the code and understand the output.
 * @author CSCI209
 */
public class ParameterPassingDemo1 {
    
    public static void main(String[] args) {
        int x = 10;
        int squared = square(x);
        System.out.println("The square of " + x + " is " +     squared);
    }

    /**
     * num copies the value of the parameter passed into the method
     */
    public static int square(int num) {
        return num*=num;
    }
}

/**
 * Demonstrates Pass By Value with a primitive type.
 * Trace through the code and understand the output
 * @author CSCI209
 */
public class ParameterPassingDemo2 {
    
    public static void main(String[] args) {
        int x = 27;
        System.out.println(x);
        doubleValue(x);
        System.out.println(x);
    }
    
    /**
     * p copies the value passed into the method
     */
    public static void doubleValue(int p) {
        p = p * 2;
    }
}