1. Elementary Programming
Chapter2:
Elementary Programming

2. Agenda Contents of chapter 2 Objectives of chapter 2
Numerical data types
Trace an execution of a calculation program
Reading input from console
Identifiers guidelines
Declaring variables
Constants
Numeric operators
Integer division
Remainder operator
Example of using remainder operators

3. Contents of chapter 2 Solve problems with programming
Java primitive data types
Related subjects to primitive data types such as :
Variables
Constants
Operators
Expressions
Input and output.

4. Objectives of chapter2:
To write Java programs to perform simple calculations (§2.2).
To obtain input from the console using the Scanner class (§2.3).
To use identifiers to name variables, constants, methods, and classes (§2.4).
To use variables to store data (§§ ).
To program with assignment statements and assignment expressions (§2.6).
To use constants to store permanent data (§2.7).
To declare Java primitive data types: byte, short, int, long, float, double, and char (§§2.8.1).
To use Java operators to write numeric expressions (§§2.8.2–2.8.3).
To display current time (§2.9).

5. Objectives of chapter2:
To use short hand operators (§2.10).
To cast value of one type to another type (§2.11).
To compute loan payment (§2.12).
To represent characters using the char type (§2.13).
To compute monetary changes (§2.14).
To represent a string using the String type (§2.15).
To become familiar with Java documentation, programming style, and naming conventions (§2.16).
To distinguish syntax errors, runtime errors, and logic errors and debug errors (§2.17).
(GUI) To obtain input using the JOptionPane input dialog boxes (§2.18).

6. Numerical data types:

7. Trace a Program Execution
animation
Trace a Program Execution
public class ComputeArea {
/** Main method */
public static void main(String[] args) {
double radius;
double area;
// Assign a radius
radius = 20;
// Compute area
area = radius * radius * ;
// Display results
System.out.println("The area for the circle of radius " +
radius + " is " + area); }
memory
radius
no value
allocate memory for radius

8. Trace a Program Execution
animation
Trace a Program Execution
public class ComputeArea {
/** Main method */
public static void main(String[] args) {
double radius;
double area;
// Assign a radius
radius = 20;
// Compute area
area = radius * radius * ;
// Display results
System.out.println("The area for the circle of radius " +
radius + " is " + area); }
memory
radius
no value
area
no value
allocate memory for area

9. Trace a Program Execution
animation
Trace a Program Execution
assign 20 to radius
public class ComputeArea {
/** Main method */
public static void main(String[] args) {
double radius;
double area;
// Assign a radius
radius = 20;
// Compute area
area = radius * radius * ;
// Display results
System.out.println("The area for the circle of radius " +
radius + " is " + area); }
radius 20
area
no value

10. Trace a Program Execution
animation
Trace a Program Execution
public class ComputeArea {
/** Main method */
public static void main(String[] args) {
double radius;
double area;
// Assign a radius
radius = 20;
// Compute area
area = radius * radius * ;
// Display results
System.out.println("The area for the circle of radius " +
radius + " is " + area); }
memory
radius 20
area
compute area and assign it to variable area

11. Trace a Program Execution
animation
Trace a Program Execution
public class ComputeArea {
/** Main method */
public static void main(String[] args) {
double radius;
double area;
// Assign a radius
radius = 20;
// Compute area
area = radius * radius * ;
// Display results
System.out.println("The area for the circle of radius " +
radius + " is " + area); }
memory
radius 20
area
print a message to the console

12. Reading input from console
Create a Scanner object
Scanner input = new Scanner(System.in);
2. Use the methods next(), nextByte(), nextShort(), nextInt(), nextLong(), nextFloat(), nextDouble(), or nextBoolean() to obtain to a string, byte, short, int, long, float, double, or boolean value.
Example:
System.out.print("Enter a double value: ");
double d = input.nextDouble();

13. Identifiers guidelines:
An identifier is a sequence of characters that consist of letters, digits, underscores (_), and dollar signs ($).
It must start with a letter, an underscore (_), or a dollar sign ($).
It cannot start with a digit.
An identifier cannot be a reserved word. (See Appendix A, “Java Keywords,” for a list of reserved words).
An identifier cannot be true, false, or null.
An identifier can be of any length.

14. Assignment Statements
Declaring Variables
int x; // Declare x to be an
// integer variable;
double radius; // Declare radius to
// be a double variable;
char a; // Declare a to be a
// character variable;
Assignment Statements
x = 1; // Assign 1 to x;
radius = 1.0; // Assign 1.0 to radius;
a = 'A'; // Assign 'A' to a;

15. Declaring and Initializing in One Step
int x = 1;
double d = 1.4;

16. Declaration structure:
Constants
Constant variable value cannot be changed and all data type may be declared as constant using final.
Declaration structure:
final datatype CONSTANTNAME = VALUE;
Example:
final double PI = ;
final int SIZE = 3;

17. Numeric operators

18. 1 the remainder of the division
Integer Division
/ for the Quotient
% for the Remainder
Type of the output depends on the 2 input types
Example:
output
input
2 integer
5/2
2.0 double
5.0/2
1 the remainder of the division
5%2

19. Remainder Operator
Remainder is very useful in programming.
Example:an even number % 2 is always 0 and an odd number % 2 is always 1. So you can use this property to determine whether a number is even or odd.

21. Example of using remainder operator:
Suppose today is Saturday and you and your friends are going to meet in 10 days. What day is in 10 days? You can find that day is Tuesday using the following expression:
Note: Week starts on Monday
Day1: Monday, Day2: Tuesday, Day3: Wednesday,
Day4: Thursday, Day5:Firday, Day6:Saturday, Day7: Sunday