Section 8.11 WrClasses-WE4-P2
Subsection 8.11.1 Subgoals for Writing a Class 4/4
Name it
Differentiate class-level (static) vs. instance/object-level variables
Differentiate class-level (static) vs. instance/object behaviors/methods
-
Define class variables (static) as needed ‘
Name
Data Type
public / private / final
-
Define instance variables (that you want to be interrelated)
Name
Data Type
private
-
Create constructor (behavior) that creates initial state of object
public
Same name as class
No return type
Default - no parameters
Logic - initialize all variables
Repeat as needed, adding parameters
Create 1 accessor and 1 mutator behaviors per attribute
Accessors
Name is get_<attr_name>
Public
Return type same data type as attribute
No parameters
Logic - return value
-
Write toString method
public
Returns String
No parameters
Logic - convert needed attributes to a format that can be printed
-
Write equals method
public
Returns boolean
Parameter - instance of the class
Logic - compare attributes for equity
Create additional methods as needed
Subsection 8.11.2 Classes-WE4-P2
Exercises Exercises
1.
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.
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.
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.
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.
Identify the helper or auxiliary 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;:
}
}
You have attempted of activities on this page.