HW - 2019 FRQ 2 -

(rest of HW quiz has already been submitted)

public class StepTracker {
    private int days;
    private int activeDays;
    private int totalSteps;
    private int minActive;

    public StepTracker(int m) {
        minActive = m;
        days = 0;
        activeDays = 0;
        totalSteps = 0;
    }

    public int activeDays() {
        return activeDays;
    }

    public double averageSteps() {
        if (days == 0) {
            return 0.0;
        }
        return double totalSteps / days;
    }

    public void addDailySteps(int steps) {
        days++;
        totalSteps += steps;
        if (steps >= minActive) {
            activeDays++;
        }
    }
}

public class Cow {

    // instance variables
    private String cowType;
    private String sound;
    private int numMilkings;

    // constructor
    public Cow (String cowType, String sound){
        this.numMilkings = 0;
        this.cowType = cowType;
        this.sound = sound;
    }
}

public class Cow {

    // instance variables
    private String cowType;
    private String sound;
    private int numMilkings;

    // default constructor
    public Cow(){
        this.numMilkings = 0;
        this.cowType = null;
        this.sound = null;
    }

    // all-args constructor
    public Cow(String cowType, String sound, int numMilkings){
        this.numMilkings = numMilkings;
        this.cowType = cowType;
        this.sound = sound;
    }
    

    public Cow (String cowType, String sound){
        this.numMilkings = 0;
        this.cowType = cowType;
        this.sound = sound;
    }

    public static void main(String[] args) {
        Cow firstCow = new Cow("holstein", "moo");
        Cow secondCow = new Cow();
        Cow thirdCow = new Cow("holstein", "moo", 100);
    }
}

Cow.main(null);

Constructors -

  • Default Constructor: no parameters
    • Sets instance variables equal to default values
      • String: null
      • Int/Double: 0
    • Java provides a no-argument default constructor if there are no constructors inside the class
    • Instance variables set to default values

Procedural Abstraction Tip -

  • When you see repeated code, that is a signal for you to make a new method!
  • Benefits -
    • organize our code by function
    • reduce complexity
    • reduce the repetition of code
    • reuse code by putting it in a method and calling it whenever needed
    • help with debugging and maintenance
    • changes to that block of code only need to happen in one place

3 steps to create and call a method -

  1. Object of the class
    • Declare an object of your class in the main method or from outside the class.
  2. Method call
    • Whenever you want to use the method, call -
  3. Method definition
    • Write the method’s header and body code like below:
// Step 1
Classname objectName = new Classname();

// Step 2
objectName();

//Step 3
    // method header
    public void methodName() {
        // method body for the code
    }

public class Cow {

    // instance variables
    private String cowType;
    private String sound;
    private int numMilkings;

    public Cow (String cowType, String sound){
        this.numMilkings = 0;
        this.cowType = cowType;
        this.sound = sound;
    }

    public int getNumMilkings(){
        return numMilkings;
    }

    public void setSound(String sound){
        this.sound = sound;
    }

    public String toString(){
        return "Type of Cow: " + cowType + "; " + "Sound: " + sound + "; " + "Number of Milkings: " + numMilkings;
    }

    public static void main(String[] args) {
        Cow firstCow = new Cow("holstein", "moo");
        System.out.println(firstCow);
        System.out.println("Number of Milkings: " + firstCow.getNumMilkings());
        firstCow.setSound("oink!");
        System.out.println("Mutated Cow:" + firstCow);
    }
}

Cow.main(null);