2 meetings every week Tuesday and Thursday

Each day has two timeslots for

• Eastern timezones and American early risers

• Western timezones and American afternoons

• Make sure to keep up with the calendar for links and timings

Format

• 3 practice problems every session

• focused on practical understanding of concepts covered recently in class

• slides and material available after class

How to follow along

• Small breakout rooms of working together

• Work for 10-15 minutes together, feel free to use paper, whiteboards, online share tools.

• Use the jeed playground on the 125 homepage for the interactive running

1) Getters and Setters

• In java all the instance variables are private

• To read them we use getters, for String name you might have a function called String getName()

• To write to them we use setters, for String name you might have a function called void setName(String setName)

1) Getters and Setters - Example

public class Country {
    private String name;
    public String getName() {
        return name;
    }

    public void setName(String setName) {
        name = setName;
    }
}

1) Getters and Setters - Practice

• Write a class Pet that has one field int age

• Create getAge() and setAge(int)

1) Getters and Setters - Starter code (10 minutes)

public class Pet {
  // implement
}

2) Constructor Overloading

• You can overload many constructors much like functions.

• This is to deal with a variety of inputs.

• Each constructor has different parms but the same name as the class.

• You can use the this keyword to call other constructors.

2) Constructor Overloading - Example

public class Country {
    private String name;
    
    public Country() {
        name = "India"; // default
    }

    public Country(String setName) {
        name = setName;
    }
}

2) Constructor Overloading Practice - Practice

• This time Pet should have two fields, String name and int age

• One constructor should take a String for name and the default age should be set at 6

• The other should take both a String for name and an int for age.

2) Constructor Overloading Starter Code (10 minutes)

public class Pet {
  // implement 
  // don't worry about getters and setters
}

3) OOP Functionality

• Classes encapsulate state and behavious

• For behavious we can make instance methods inside a class which use the instance variables.

• These can't have the keyword static (more next time)

3) OOP Functionality - Example

public class Circle {
    private int radius;
    [...]
    public int circumference() {
        return 2 * Math.PI * radius;
    }
}

3) OOP Functionality - Practice

• Model a class Student with two midterms and one final score as double

• Create a function grade which takes no parameters and returns a double. $grade = 0.2 midterm1 + 0.3 midterm 2 + 0.5 final.

3) OOP Functionality - Starter code (15 minutes)

class Student {
    // define variables

    double grade() {
        return 0.0; // todo
    }
}

Spoiler alert :P

1) Getters and Setters - Starter code (10 minutes)

public class Pet {
  private int age = 0;
  public int getAge() { 
    return age; 
  }
  public void setAge(int setAge) { 
    age = setAge; 
  }
}

2) Constructor Overloading

public class Pet {
  private String name;
  private int age;
  public Pet(String setName) {
      name = setName;
      age = 6;
  }

  public Pet(String setName, int setAge) {
      name = setName;
      age = setAge;
  }
}

3) OOP Functionality

class Student {
    private double midterm1;
    private double midterm2;
    private double finalScore;

    double grade() {
        return 0.2*midterm1 + 0.3*midterm2 + 0.5 * finalScore; // todo
    }
}