5.1 Anatomy of a Class

Class: blueprint used to create objects
Instances, attributes, constructors, methods
Objects: instances of a class
public: no restricted access -- classes and constructors
private: restrict access -- instance variables

5.2 Constructors

initializes instance variables when an object is created
Each object has attributes which are the instance of a class
Constructors set the initial state of an object by assigning initial values to instance variables

5.3 Comments

ignored by compiler
make code more readable
not required for the AP exam

5.4 Accessor Method

Allows objects outside of the class to obtain values
non void returns a single value
toString() Method

5.5 Mutator Method

Don't return values
Must be used when different classes need to modify instance variables

public class cow {
}
Cow myCow = new Cow();

public class Snack{
    private String name; // instance variable 1
    private int calories; // instance variable 2

    public Snack(){ // constructor with no argument
        name = null; 
        calories = 0; 
    }
    public Snack (String n, int c){
        name = n;
        calories = x;
    }
    public String getName(){ // calling a method and accessor
        return name;
    }
    public int getCalories(){
        return calories;
    }
    public void setName(String n){
        name = n;
    }
    public static void main(String[] args){
        Snack one = new Snack("Chips", 100);
        System.out.println(one.getName());
    }
}
Snack.main(null);

2019 FRQ Question 2

public class StepTracker
{
    private int minSteps;
    private int totalSteps;
    private int numDays;
    private int numActiveDays;
    public StepTracker(int threshold)
    {
        minSteps = threshold;
        totalSteps = 0;
        numDays = 0;
        numActiveDays = 0;
    }
    public void addDailySteps(int steps)
    {
        totalSteps += steps;
        numDays++;
        if (steps >= minSteps)
        {
            numActiveDays++;
        }
    }
    public int activeDays()
    {
        return numActiveDays;
    }
    public double averageSteps()
    {
        if (numDays == 0)
        {
            return 0.0;
        }
        else
        {
            return (double) totalSteps / numDays;
        }
    }
}