An introduction to the basics of OOP - declaring and using classes

1. Classes and Objects Defining Classes and Objects

3. Defining S imple C lasses

7. Defining S imple C lasses Examples

10. Defining Simple Class (2) public Cat() { this.name = "Nastradin"; } public Cat(String name) { this.name = name; } public void s ayMiau() { System.out.printf( "Cat %s said: Miauuuuuu!%n", name); } } Method definition Constructor definition Constructor definition

11. Using C lasses

14. Using C lasses Example

17. Manipulating Class Instances (2) Cat[] cats = new Cat[] { firstCat, secondCat, thirdCat }; for(Cat cat : cats) { cat.SayMiau(); } }

18. Using C lasses in Java Live Demo

19. Constructors Defining and Using Constructors in the Classes

22. Constructors Examples

23. Defining Constructors public class Person { private String name; private int age; // Default constructor public Person() { this.name = null; this.age = 0; } // Constructor with parameters public Person(String name, int age) { this.name = name; this.age = age; } //More code ... }

26. Constructors Live Demo

27. Properties Defining and Using Properties

30. Properties Examples

31. Capsulate Fields public class Point { private int xCoord; private int yCoord; // constructing code ... public int getXCoord() { return this.xCoord; } public void setXCoord(int value) { this.xCoord = value; } public int get Y Coord() { return this. y Coord; } public void set Y Coord(int value) { this. y Coord = value; } // More code ... } Fields are encapsulated as private members Getters and Setter allow controlled access to the private fields

33. Properties Live Demo

34. Static Members Static vs. Instance Fields, Methods and Properties

37. Static Members Examples

38. Static Members – Example public class Sequence { private static int currentValue = 0; private Sequence() { // Deny instantiation of this class } public static int nextValue() { currentValue++; return currentValue; } } public class TestSequence { public static void main(String[] args) { System.out.printf("Sequence[1..3]: %d, %d, %d ", Sequence.nextValue(), Sequence.nextValue(), Sequence.nextValue()); } }

39. Static Members Live Demo

40. Creating Static Methods public class Fraction { private int numerator; private int denominator; public Fraction(int num, int denom) { this.numerator = num; this.denominator = denom; } public static Fraction Parse( S tring val) { S tring[] parts = val. s plit( " / " ); int num = Integer.parseInt(parts[0]); int denom = Integer.parseInt(parts[1]); Fraction result = new Fraction(num, denom); return result; } }

42. Parsing Fractions Live Demo