WrClasses-WE4-P2

Section 10.11 WrClasses-WE4-P2

Subgoals for Writing a Class.

Pick a name for the class, is usually a noun
🔗

🔗
Differentiate class-level static vs. instance/object-level variables
🔗

🔗
Differentiate class-level static vs. instance/object behaviors/methods
🔗

🔗
Define instance variables (that you want to be interrelated)
🔗
1. Name
  🔗
  
  🔗
2. Data Type
  🔗
  
  🔗
3. private
  🔗
  
  🔗
🔗
🔗
Define class variables static as needed
🔗
1. Name
  🔗
  
  🔗
2. Data Type
  🔗
  
  🔗
3. public / private / final
  🔗
  
  🔗
🔗
🔗
Create constructor (behavior) that creates initial state of object
🔗
1. Overloaded constructor (with as many parameters)
  🔗
  
  🔗
2. public
  🔗
  
  🔗
3. Same name as class
  🔗
  
  🔗
4. No return type
  🔗
  
  🔗
5. Default - no parameters
  🔗
  
  🔗
6. Logic - initialize all variables
  🔗
  
  🔗
7. Repeat as needed, adding parameters
  🔗
  
  🔗
🔗
🔗
Create 1 accessor and 1 mutator behaviors per attribute
🔗
1. Accessors
  🔗
  1. Name is get_<attr_name>
    🔗
    
    🔗
  2. Public
    🔗
    
    🔗
  3. Return type same data type as attribute
    🔗
    
    🔗
  4. No parameters
    🔗
    
    🔗
  5. Logic - return value
    🔗
    
    🔗
  🔗
  🔗
2. Mutators
  🔗
  1. Name is set_<attr_name>
    🔗
    
    🔗
  2. Public
    🔗
    
    🔗
  3. Return type is void
    🔗
    
    🔗
  4. Parameter is same data type as attribute
    🔗
    
    🔗
  5. Logic validates input parameter and sets attribute value
    🔗
    
    🔗
  🔗
  🔗
🔗
🔗
Write toString method
🔗
1. public
  🔗
  
  🔗
2. Returns String
  🔗
  
  🔗
3. No parameters
  🔗
  
  🔗
4. Logic - convert needed attributes to a format that can be printed
  🔗
  
  🔗
🔗
🔗
Write equals method
🔗
1. public
  🔗
  
  🔗
2. Returns boolean
  🔗
  
  🔗
3. Parameter - instance of the class
  🔗
  
  🔗
4. Logic - compare attributes for equity
  🔗
  
  🔗
🔗
🔗
Create additional methods as needed
🔗

🔗

🔗

Subsection 10.11.1

Exercises Exercises

1.

Q51: Identify all constructors.

🔗

/* Coins Class */
public class Coins {
    private int quarters;
    private int dimes;
    private int nickels;
    private int pennies;

    public Coins(int newQuarters, int newDimes, int newNickels, int newPennies) {
        setQuarters( newQuarters );
        setDimes( newDimes );
        setNickels( newNickels );
        setPennies( newPennies );
    }

    public Coins() {
        setQuarters( 0 );
        setDimes( 0 );
        setNickels( 0 );
        setPennies( 0 );
    }

    public int getQuarters() {
        return quarters;
    }

    public void setQuarters(int newQuarters) {
        if ( newQuarters >= 0 )
            quarters = newQuarters;
        else {
            System.out.println( "The number of quarters cannot be negative." );
            System.out.println( "Value not changed." );
      }
    }

    public int getDimes()  {
        return dimes;
    }

    public void setDimes(int newDimes) {
        if ( newDimes >= 0 )
            dimes = newDimes;
        else {
            System.out.println( "The number of dimes cannot be negative." );
            System.out.println( "Value not changed." );
        }
    }

    public int getNickels() {
        return nickels;
    }

    public void setNickels(int newNickels) {
        if ( newNickels >= 0 )
            nickels = newNickels;
        else {
            System.out.println( "The number of nickels cannot be negative." );
            System.out.println( "Value not changed." );
        }
    }

    public int getPennies() {
        return pennies;
    }

    public void setPennies(int newPennies) {
        if ( newPennies >= 0 )
            pennies = newPennies;
        else {
            System.out.println( "The number of pennies cannot be negative." );
            System.out.println( "Value not changed." );
        }
    }

    public String toString( ) {
        return( "quarters: " + quarters + "; dimes: " + dimes
        + "; nickels: " + nickels + "; pennies:" + pennies );
    }

    public boolean equals(Coins c)  {
        return (quarters == c.quarters&& dimes == c.dimes
        && nickels == c.nickels&& pennies == c.pennies);
    }

    private double moneyFromQuarters()  {
        return ( quarters * .25 );
    }

    private double moneyFromDimes()  {
        return ( dimes * .1 );
    }

    private double moneyFromNickels()  {
        return ( nickels * .05 );
    }

    private double moneyFromPennies() {
        return ( pennies * .01 );
    }

    public double total() {
        return moneyFromQuarters() +
        moneyFromDimes() +
        moneyFromNickels() +
        moneyFromPennies();
    }

    public double convert(double rate) {
        return total() * rate;
    }
}

🔗

2.

Q52: Identify all accessor/getter methods.

🔗

/* Coins Class */
public class Coins {
    private int quarters;
    private int dimes;
    private int nickels;
    private int pennies;

    public Coins(int newQuarters, int newDimes, int newNickels, int newPennies) {
        setQuarters( newQuarters );
        setDimes( newDimes );
        setNickels( newNickels );
        setPennies( newPennies );
    }

    public Coins() {
        setQuarters( 0 );
        setDimes( 0 );
        setNickels( 0 );
        setPennies( 0 );
    }

    public int getQuarters() {
        return quarters;
    }

    public void setQuarters(int newQuarters) {
        if ( newQuarters >= 0 )
            quarters = newQuarters;
        else {
            System.out.println( "The number of quarters cannot be negative." );
            System.out.println( "Value not changed." );
      }
    }

    public int getDimes()  {
        return dimes;
    }

    public void setDimes(int newDimes) {
        if ( newDimes >= 0 )
            dimes = newDimes;
        else {
            System.out.println( "The number of dimes cannot be negative." );
            System.out.println( "Value not changed." );
        }
    }

    public int getNickels() {
        return nickels;
    }

    public void setNickels(int newNickels) {
        if ( newNickels >= 0 )
            nickels = newNickels;
        else {
            System.out.println( "The number of nickels cannot be negative." );
            System.out.println( "Value not changed." );
        }
    }

    public int getPennies() {
        return pennies;
    }

    public void setPennies(int newPennies) {
        if ( newPennies >= 0 )
            pennies = newPennies;
        else {
            System.out.println( "The number of pennies cannot be negative." );
            System.out.println( "Value not changed." );
        }
    }

    public String toString( ) {
        return( "quarters: " + quarters + "; dimes: " + dimes
        + "; nickels: " + nickels + "; pennies:" + pennies );
    }

    public boolean equals(Coins c)  {
        return (quarters == c.quarters&& dimes == c.dimes
        && nickels == c.nickels&& pennies == c.pennies);
    }

    private double moneyFromQuarters()  {
        return ( quarters * .25 );
    }

    private double moneyFromDimes()  {
        return ( dimes * .1 );
    }

    private double moneyFromNickels()  {
        return ( nickels * .05 );
    }

    private double moneyFromPennies() {
        return ( pennies * .01 );
    }

    public double total() {
        return moneyFromQuarters() +
        moneyFromDimes() +
        moneyFromNickels() +
        moneyFromPennies();
    }

    public double convert(double rate) {
        return total() * rate;
    }
}

🔗

3.

Q53: Identify all mutator/setter methods.

🔗

/* Coins Class */
public class Coins {
    private int quarters;
    private int dimes;
    private int nickels;
    private int pennies;

    public Coins(int newQuarters, int newDimes, int newNickels, int newPennies) {
        setQuarters( newQuarters );
        setDimes( newDimes );
        setNickels( newNickels );
        setPennies( newPennies );
    }

    public Coins() {
        setQuarters( 0 );
        setDimes( 0 );
        setNickels( 0 );
        setPennies( 0 );
    }

    public int getQuarters() {
        return quarters;
    }

    public void setQuarters(int newQuarters) {
        if ( newQuarters >= 0 )
            quarters = newQuarters;
        else {
            System.out.println( "The number of quarters cannot be negative." );
            System.out.println( "Value not changed." );
      }
    }

    public int getDimes()  {
        return dimes;
    }

    public void setDimes(int newDimes) {
        if ( newDimes >= 0 )
            dimes = newDimes;
        else {
            System.out.println( "The number of dimes cannot be negative." );
            System.out.println( "Value not changed." );
        }
    }

    public int getNickels() {
        return nickels;
    }

    public void setNickels(int newNickels) {
        if ( newNickels >= 0 )
            nickels = newNickels;
        else {
            System.out.println( "The number of nickels cannot be negative." );
            System.out.println( "Value not changed." );
        }
    }

    public int getPennies() {
        return pennies;
    }

    public void setPennies(int newPennies) {
        if ( newPennies >= 0 )
            pennies = newPennies;
        else {
            System.out.println( "The number of pennies cannot be negative." );
            System.out.println( "Value not changed." );
        }
    }

    public String toString( ) {
        return( "quarters: " + quarters + "; dimes: " + dimes
        + "; nickels: " + nickels + "; pennies:" + pennies );
    }

    public boolean equals(Coins c)  {
        return (quarters == c.quarters&& dimes == c.dimes
        && nickels == c.nickels&& pennies == c.pennies);
    }

    private double moneyFromQuarters()  {
        return ( quarters * .25 );
    }

    private double moneyFromDimes()  {
        return ( dimes * .1 );
    }

    private double moneyFromNickels()  {
        return ( nickels * .05 );
    }

    private double moneyFromPennies() {
        return ( pennies * .01 );
    }

    public double total() {
        return moneyFromQuarters() +
        moneyFromDimes() +
        moneyFromNickels() +
        moneyFromPennies();
    }

    public double convert(double rate) {
        return total() * rate;
    }
}

🔗

4.

Q54: Identify the attributes.

🔗

/* Coins Class */
public class Coins {
    private int quarters;
    private int dimes;
    private int nickels;
    private int pennies;

    public Coins(int newQuarters, int newDimes, int newNickels, int newPennies) {
        setQuarters( newQuarters );
        setDimes( newDimes );
        setNickels( newNickels );
        setPennies( newPennies );
    }

    public Coins() {
        setQuarters( 0 );
        setDimes( 0 );
        setNickels( 0 );
        setPennies( 0 );
    }

    public int getQuarters() {
        return quarters;
    }

    public void setQuarters(int newQuarters) {
        if ( newQuarters >= 0 )
            quarters = newQuarters;
        else {
            System.out.println( "The number of quarters cannot be negative." );
            System.out.println( "Value not changed." );
      }
    }

    public int getDimes()  {
        return dimes;
    }

    public void setDimes(int newDimes) {
        if ( newDimes >= 0 )
            dimes = newDimes;
        else {
            System.out.println( "The number of dimes cannot be negative." );
            System.out.println( "Value not changed." );
        }
    }

    public int getNickels() {
        return nickels;
    }

    public void setNickels(int newNickels) {
        if ( newNickels >= 0 )
            nickels = newNickels;
        else {
            System.out.println( "The number of nickels cannot be negative." );
            System.out.println( "Value not changed." );
        }
    }

    public int getPennies() {
        return pennies;
    }

    public void setPennies(int newPennies) {
        if ( newPennies >= 0 )
            pennies = newPennies;
        else {
            System.out.println( "The number of pennies cannot be negative." );
            System.out.println( "Value not changed." );
        }
    }

    public String toString( ) {
        return( "quarters: " + quarters + "; dimes: " + dimes
        + "; nickels: " + nickels + "; pennies:" + pennies );
    }

    public boolean equals(Coins c)  {
        return (quarters == c.quarters&& dimes == c.dimes
        && nickels == c.nickels&& pennies == c.pennies);
    }

    private double moneyFromQuarters()  {
        return ( quarters * .25 );
    }

    private double moneyFromDimes()  {
        return ( dimes * .1 );
    }

    private double moneyFromNickels()  {
        return ( nickels * .05 );
    }

    private double moneyFromPennies() {
        return ( pennies * .01 );
    }

    public double total() {
        return moneyFromQuarters() +
        moneyFromDimes() +
        moneyFromNickels() +
        moneyFromPennies();
    }

    public double convert(double rate) {
        return total() * rate;
    }
}

🔗

5.

Q55: Identify the helper or auxiliary methods. Often any method that doesn’t fall into another category (constructor, accessor, mutator, toString, equals) is considered a helper or auxiliary method.

🔗

/* Coins Class */
public class Coins {
    private int quarters;
    private int dimes;
    private int nickels;
    private int pennies;

    public Coins(int newQuarters, int newDimes, int newNickels, int newPennies) {
        setQuarters( newQuarters );
        setDimes( newDimes );
        setNickels( newNickels );
        setPennies( newPennies );
    }

    public Coins() {
        setQuarters( 0 );
        setDimes( 0 );
        setNickels( 0 );
        setPennies( 0 );
    }

    public int getQuarters() {
        return quarters;
    }

    public void setQuarters(int newQuarters) {
        if ( newQuarters >= 0 )
            quarters = newQuarters;
        else {
            System.out.println( "The number of quarters cannot be negative." );
            System.out.println( "Value not changed." );
      }
    }

    public int getDimes()  {
        return dimes;
    }

    public void setDimes(int newDimes) {
        if ( newDimes >= 0 )
            dimes = newDimes;
        else {
            System.out.println( "The number of dimes cannot be negative." );
            System.out.println( "Value not changed." );
        }
    }

    public int getNickels() {
        return nickels;
    }

    public void setNickels(int newNickels) {
        if ( newNickels >= 0 )
            nickels = newNickels;
        else {
            System.out.println( "The number of nickels cannot be negative." );
            System.out.println( "Value not changed." );
        }
    }

    public int getPennies() {
        return pennies;
    }

    public void setPennies(int newPennies) {
        if ( newPennies >= 0 )
            pennies = newPennies;
        else {
            System.out.println( "The number of pennies cannot be negative." );
            System.out.println( "Value not changed." );
        }
    }

    public String toString( ) {
        return( "quarters: " + quarters + "; dimes: " + dimes
        + "; nickels: " + nickels + "; pennies:" + pennies );
    }

    public boolean equals(Coins c)  {
        return (quarters == c.quarters&& dimes == c.dimes
        && nickels == c.nickels&& pennies == c.pennies);
    }

    private double moneyFromQuarters()  {
        return ( quarters * .25 );
    }

    private double moneyFromDimes()  {
        return ( dimes * .1 );
    }

    private double moneyFromNickels()  {
        return ( nickels * .05 );
    }

    private double moneyFromPennies() {
        return ( pennies * .01 );
    }

    public double total() {
        return moneyFromQuarters() +
        moneyFromDimes() +
        moneyFromNickels() +
        moneyFromPennies();
    }

    public double convert(double rate) {
        return total() * rate;
    }
}

🔗

You have attempted of activities on this page.

🔗

Prev Top Next