SOURCE CODE FILES FOR Classes2 EXAMPLES

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/**
 * Project Pair3
 * Class Main
 * 
 * Demonstrate the add and equals methods
 * in the Pair class.
 */
public class Main
{
    public static void main(String[] args)
    {
        // Declare and create Pair objects.
        Pair s = new Pair();
        Pair t = new Pair(3);
        Pair u = new Pair(8, 5);
        Pair v, w;
        
        System.out.println(s + " " + t + " " + u);
        v = s.add(t);
        
        // To create w, the anonymous object
        // (2, 5) is added to t, which is (3, 3).
        w = t.add(new Pair(2, 5));
        System.out.println(v + " " + w);
        System.out.println();
        
        // a.equals(b) if and only if x and y 
        // components of object a equal the x and y
        // components of b.
        
        // a == b if and only if address in a equals
        // address in b.
        System.out.print(u.equals(u) + "  ");
        System.out.println(u == u);
        System.out.print(u.equals(w) + "  ");
        System.out.println(u == w);    
    }
}

// Output:
(0,0) (3,3) (8,5)
(3,3) (8,5)

true  true
true  false

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/**
 * Project Pair3
 * Class Pair
 * 
 * The Pair class with add and equals methods.
 */
public class Pair
{
    // Instance variables are x and y coordinates.
    private int x, y;
    
    // Noarg constructor.
    public Pair()
    {
        x = 0;
        y = 0;
    }
    
    // Constructor with one parameter.
    public Pair(int value)
    {
        x = value;
        y = value;
    }
    
    // Constructor with two arguments.
    public Pair(int xValue, int yValue)
    {
        x = xValue;
        y = yValue;
    }
    
    // Accessor method for x.
    public int getX()
    {
        return x;
    }
    
    // Accessor method for y.
    public int getY()
    {
        return y;
    }
    
    // toString method.
    public String toString()
    {
        return "(" + x + "," + y + ")";
    }
    
    // Method for adding two Pair objects.
    // Addition is defined componentwise.
    public Pair add(Pair other)
    {
        Pair returnValue;
        returnValue = new Pair(x + other.x, y + other.y);
        return returnValue;
    }
    
    // Two pair objects are equal if both of the
    // components are equal.
    public boolean equals(Pair other)
    {
        return (x == other.x && y == other.y);
    }
}

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/**
 * Project Kid4
 * Class Main
 * 
 * Test a Kid class with an equals method.
 * Two Kid objects are equal if their ages are
 * the same.  (Alternatively, two kids are equal
 * if their names are the same.)
 */
public class Main
{
    public static void main(String[] args)
    {
        Kid w = new Kid("Jane", 'F', 11);
        Kid x = new Kid("Terry", 'M', 12);
        Kid y = new Kid("Terry", 'F', 9);
        Kid z = new Kid("Scott", 'M', 11);

        System.out.println(x + "   " + y + "   " + z);
        System.out.println();
        
        System.out.print(w.equals(y) + "  ");
        System.out.print(x.equals(y) + "  ");
        System.out.println(w.equals(z) + "  ");
    }
}

// Output:
Terry M 12   Terry F 9   Scott M 11

false  false  true  

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/**
 * Project Kid4
 * Class Kid
 * 
 * A Kid class with an equals method.
 */
public class Kid
{
    // Private instance variables.
    private String name;
    private char gender;
    private int age;
    
    // Noarg constructor;
    public Kid()
    {
        name = "Unknown";
        gender = 'U';
        age = -1;
    }
    
    // Parameterized constructor, which 
    // performs data validation.
    public Kid(String aName, char aGender, int anAge)
    {
        // Don't allow empty string as a name.
        if (aName.equals(""))
            name = "Unknown";
        else
            name = aName;
            
        // Gender must be 'F' or 'M'.
        if (aGender == 'F' || aGender == 'M')
            gender = aGender;
        else
            gender = 'U';
            
        // Age must be nonnegative.
        if (anAge < 0)
            age = -1;
        else
            age = anAge;
    }
            
    // Accessor method for name.
    public String getName()
    {
        return name;
    }
    
    // Accessor method for gender.
    public char getGender()
    {
        return gender;
    }
    
    // Accessor method for name.
    public int getAge()
    {
        return age;
    }
    
    // Mutator method for gender.
    public void setGender(char aGender)
    {
        // Gender must be 'F' or 'M'.
        if (aGender == 'F' || aGender == 'M')
            gender = aGender;
        else
            gender = 'U';
    }
    
    // hasBirthday method adds 1 to age.
    public void hasBirthday()
    {
        age++;
    }
    
    // toString method returns object
    // information as a string.
    public String toString()
    {
        return name + " " + gender + " " + age;
    }
    
    // Two Kid objects are "equal" if their ages
    // are equal
    public boolean equals(Kid other)
    {
        return age == other.age;
        
        // If you want to declare two Kid objects
        // "equal" if their names are the same, use
        // the following return statement:
        // return name.equal(other.name);
    }
}

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