Data Types & Operators

1. Data Types & Operators Lecture from (Chapter 3,4)

2. Review • An introduction to Object-oriented programming • Arithmetic Operators • Bitwise operators • Relational Operators • Boolean Logical Operator • Assignment Operator

3. An introduction to Object Oriented Programming - http://java.sun.com/docs/books/tutorial/java/concepts/ • Object-oriented Programming is the core of Java. • All java programms are object-oriented. • We need to understand what an object is, what a class is, how objects and classes are related, and how objects communicate by using messages.

4. An overview of Object-oriented programming (1) • An object: An object is a software bundle of related variables and methods. Software objects are often used to model real-world objects you find in everyday life. • Messages: Software objects interact and communicate with each other using messages. • Class: A class is a prototype that defines the variables and the methods common to all objects of a certain kind.

5. An overview of Object-oriented programming (2) • An inherientence: A class inherits state and behavior from its superclass. Inheritance provides a powerful and natural mechanism for organizing and structuring software programs. • An Interface: An interface is a contract in the form of a collection of method and constant declarations. When a class implements an interface, it promises to implement all of the methods declared in that interface.

6. An object - We will introduce them one by one per week to build up your understanding • There are many examples of real-world objects. For example, our book, cat, pet etc. • These real-world objects share two characteristics, namely, : state and behavior. • For example, cats have state (color, hungry) and behavior (running , eating, sleeping). • Software objects are modeled following the real-world objects in that they too have state and behavior. • A software object maintains its state in one or more variables. • A variable is an item of data named by an identifier. • A software object implements its behavior with methods. A method is a function (subroutine) associated with an object.

7. Java Data Types • Primitive Data Types: • boolean true or false • char unicode! (16 bits) • byte signed 8 bit integer • short signed 16 bit integer • int signed 32 bit integer • long signed 64 bit integer • float,double IEEE 754 floating point not an int!

8. Arithmetic Operator – page 74 Operator Description + addition - Subtraction * Multiplication / Division % Modules ++ Increment -- Decrement

9. Example – addition and subtraction result

10. Example – multiplication and division result 0: defined as integer result

11. Special operator Expression Equivalent expression a = a + 2; a +=2; a = a – 4; a -= 4; a = a*3; a *= 3; a = a/4; a /=4; a = a%2; a %=2;

12. Example of special operator

13. Increment and Decrement Expression Equivalent expression a = a + 1; ++a; a = a – 1; --a; result

14. Bitwise Operators – page 81 Operator Description ~ Bitwise unary NOT & Bitwise AND | Bitwise OR ^ Bitwise exclusive OR >> Shift Right << Shift LEFT >>> Shift Right with zero fill

15. Operation - examples Operator Expression AND 1 & 1 = 1; 1& 0 = 0 OR 1 |1 = 1; 1| 0 = 1; 0|0 = 0 ~ 0 =~1; 1 =~0; ^ 0^ 0 = 0; 1^1 = 0; 1^0 =1; 0^1 = 1 >> 0x0010 = 0x0001 >>1 << 0x0001 = 0x0010 <<1 >>> 0x1001 = 0x0100 >>>1

16. AND Example – bits, 0x (hexadecimal) 1111 0010 (0xf2) 1111 1110 (0xfe) ---------------- (and) & 1111 0010 (0xf2) byte c = 0xf2; byte d = 0xfe; byte e = c & d; //e is 0xf2

17. OR Example • 1111 0010 (0xf2)1111 1110 (0xfe)--------------(or) |1111 1110 (0xfe) • Examplebyte c = 0xf2;byte d = 0xfe;byte e = c | d; //e is 0xfe

18. One’s complement • 1111 0010 (0xf2)-------------- ~0000 1101 (0x0d) • Examplebyte c = 0xf2;byte e = ~c; //e is 0x0d

19. EXCLUSIVE OR • 1111 0010 (0xf2)1111 1110 (0xfe)-------------- (^) 0000 1100 (0x0c)Example • byte c = 0xf2;byte d = 0xfe;byte e = c ^ d; //e is 0x0c

20. Example result

21. Relational Operators Operator Description == Equal to != Not equal to > Greater than < Less than >= Grater than or equal to <= Less than or equal to

22. Example int a = 3; int b = 4; boolean c = (a>b); //c is false boolean d = (a<b); //c is true boolean e = (a==b); //c is false boolean d = (a>=b); //c is false

23. Example

24. SHIFT >> (right) by one bit • 1111 0010 (0xf2)>> 1 (shift right by one bit)--------------------- • 0111 0001 (0x79) • Examplebyte c = 0xf2;byte e = c >>1; //e is 0x79

25. SHIFT >> by two bits • 1111 0010 (0xf2)>> 2 (shift right by one bit)--------------------- • 0011 1100 (0x3c)Example • byte c = 0xf2;byte e = c >>2; //e is 0x3c

26. SHIFT << (left) by one bit • 1111 0010 (0xf2)<< 1 (shift right by one bit)--------------------- • 1110 0100 (0xe4) • Examplebyte c = 0xf2;byte e = c <<1; //e is 0xe4

27. SHIFT << by two bits • 1111 0010 (0xf2)>> 2 (shift right by one bit)--------------------- • 1100 1000 (0xc8)Example • byte c = 0xf2;byte e = c <<2; //e is 0xc8

28. Results or bit operation (example) (1 | 2) == 3 (1 | 3) == 3 (1 & 2) == 0 (1 & 3) == 1 (0 ^ 3) == 3 (1 ^ 3) == 2 (3 ^ 3) == 0 ~0 == -1 (signed) or 255 (unsigned)

29. Example of shift result

30. Relational Operators Operator Description == Equal to != Not equal to > Greater than < Less than >= Grater than or equal to <= Less than or equal to

31. Example int a = 3; int b = 4; boolean c = (a>b); //c is false boolean d = (a<b); //c is true boolean e = (a==b); //c is false boolean d = (a>=b); //c is false

32. ? operator • It is used to replace if-then-else statement • Expression1 ? Expression2: Expression 3; • If (expression1) is true, it will evaluate Expression 2, else Expression 3 int i = 3; int j = 4; int k; (i > j)? k = 10: k = 20;// (i > j) is false, k =20

33. Summary • Object-oriented Programming is the core of Java. Each object consists of states and behaviour. • Arithmetic Operators -- +, - * /, ++, --, % • Bitwise operators -- ~, ^, &, ^, >>, <<, >>> • Relational operators -- ==, !=, >, < , >=, <= • Boolean Logical Operator -- &. |, !, &= • ? Operator – Exp1? Exp2: Exp3