1. Chapter 2: Basic Elements of Java
Java Programming:
Program Design Including Data Structures

2. Chapter Objectives
Become familiar with the basic components of a Java program, including methods, special symbols, and identifiers
Explore primitive data types
Discover how to use arithmetic operators
Examine how a program evaluates arithmetic expressions
Explore how mixed expressions are evaluated
Java Programming: Program Design Including Data Structures

3. Chapter Objectives (continued)
Learn about type casting
Become familiar with the String type
Learn what an assignment statement is and what it does
Discover how to input data into memory by using input statements
Become familiar with the use of increment and decrement operators
Java Programming: Program Design Including Data Structures

4. Chapter Objectives (continued)
Examine ways to output results using output statements
Learn how to import packages and why they are necessary
Discover how to create a Java application program
Explore how to properly structure a program, including using comments to document a program
Java Programming: Program Design Including Data Structures

5. Introduction
Computer program: A sequence of statements designed to accomplish a task
Programming: The process of planning and creating a program
Java Programming: Program Design Including Data Structures

6. The Basics of a Java Program
Java program: A collection of classes
There is a main method in every Java application program
Java Programming: Program Design Including Data Structures

7. The Basics of a Java Program
public class TheClass {
. . . }
public static void main(String[] argv) { … }
Java Programming: Program Design Including Data Structures

8. Special Symbols
Java Programming: Program Design Including Data Structures

9. Word Symbols void int public float static double throws char return
Java Programming: Program Design Including Data Structures

10. Java Identifiers Names of things Consists of:
Letters
Digits
The underscore character (_)
The dollar sign ($)
Must begin with a letter, underscore, or the dollar sign
Java Programming: Program Design Including Data Structures

11. Illegal Identifiers
Java Programming: Program Design Including Data Structures

12. Data Types A set of values together with a set of operations
Java Programming: Program Design Including Data Structures

13. Primitive Data Types
Java Programming: Program Design Including Data Structures

14. Primitive Data Types (continued)
Floating-point data types:
Float: Precision = 6 or 7
I owe the bank $12, on my car loan
Double: Precision = 15
The Outstanding Public Debt as of 05 Sep 2007 at 01:44:50 AM GMT
is: $ 8,997,049,881,
Java Programming: Program Design Including Data Structures

15. Primitive Data Types (continued)
Boolean:
True
False
Java Programming: Program Design Including Data Structures

16. Integral Data Types
Java Programming: Program Design Including Data Structures

17. Values and Memory Allocation for Integral Data Types
Java Programming: Program Design Including Data Structures

18. Arithmetic Operators and Operator Precedence
Five arithmetic operators:
+ addition
- subtraction
* multiplication
/ division
% mod (modulus)
Unary operator: An operator that has one operand (negation, absolute value, …)
Binary operator: An operator that has two operands (addition, subtraction, …)
Java Programming: Program Design Including Data Structures

19. Order of Precedence 1: * / % (same precedence)
Operators in group 1 have a higher precedence than operators in group 2
When operators have same level of precedence, operations are performed from left to right (lexicographical order)
Use parenthesis to break any ambiguities.
Java Programming: Program Design Including Data Structures

20. Expressions Integral expressions Floating-point or decimal expressions
Mixed expressions
Java Programming: Program Design Including Data Structures

21. Integral Expressions All operands are integers Examples: 2 + 3 * 5
3 + x – y / 7
x + 2 * (y – z) + 18
Java Programming: Program Design Including Data Structures

22. Integral Expressions Pierre de Fermat (France, 1601-1665)
Fermat is considered to be one of the 'fathers' of analytic geometry. (Along with Rene' Descartes.)
Fermat along with Blaise Pascal is also considered to be one of the founders of probability theory.
Fermat also made contributions in the field of optics and provided a law on light travel and made wrote a few papers about calculus well before Isaac Newton and Gottfried Leibniz were actually born.
Fermat's most important work was done in the development of modern number theory which was one of his favorite areas in math.
He is best remembered for his number theory, in particular for Fermat's Last Theorem. This theorem states that: xn + yn = zn has no non-zero integer solutions for x, y and z when n is greater than 2.
This theorem remained without a proof for about 350 years until 1993 when Andrew J. Wiles provided the first proof.
Java Programming: Program Design Including Data Structures

23. Floating-Point Expressions
All operands are floating-point numbers
Examples:
12.8 * 17.5 – 34.50
x * y – 16.2
Java Programming: Program Design Including Data Structures

24. Mixed Expressions Operands of different types Examples: 2 + 3.5
6 /
Integer operands yield an integer result; floating-point numbers yield floating-point results
If both types of operands are present, the result is a floating-point number
Precedence rules are followed
Java Programming: Program Design Including Data Structures

25. Type Conversion (Casting)
Used to avoid implicit type coercion
Syntax:
(dataTypeName) expression
Expression evaluated first, then type converted to: dataTypeName
Examples:
(int)( ) = 14
(int)(7.9) + (int)(6.7) = 13
Java Programming: Program Design Including Data Structures

26. The class String Used to manipulate strings String:
Sequence of zero or more characters
Enclosed in double quotation marks (“Hola”)
Null or empty strings have no characters (“”)
Numeric strings consist of integers or decimal numbers ( ,456.78)
Length is the number of characters in a string
Java Programming: Program Design Including Data Structures

27. Input Named constant Cannot be changed during program execution
Declared by using the reserved word final
Initialized when it is declared
Example 2-11
final double PI = ;
final double CENTIMETERS_PER_INCH = 2.54;
final int NO_OF_STUDENTS = 20;
final char BLANK = ' ';
final char USD = '$';
final double PAY_RATE = 15.75;
Java Programming: Program Design Including Data Structures

28. Input (continued) Variable (name, value, data type, size)
Content may change during program execution
Must be declared before it can be used
May not be automatically initialized
If new value is assigned, old one is destroyed
Value can only be changed by an assignment statement or an input (read) statement
Example 2-12
double amountDue;
int counter;
char ch;
int x, y;
Java Programming: Program Design Including Data Structures

29. Input (continued) Variable (name, value, data type, size)
double amountDue = ;
Name: amountDue
Value:
Type: double
Size: 6
Java Programming: Program Design Including Data Structures

30. Input (continued) The Assignment Statement variable = expression;
Example 2-13
int i, j;
double sale;
char first;
String str;
i = 4;
j = 4 * ;
sale = 0.02 * 100.0;
first = 'D';
str = "It is a sunny day";
Java Programming: Program Design Including Data Structures

31. Input (continued) Standard input stream object is System.in
Input numeric data to program
Separate by blanks, lines, or tabs
To read data:
Create an input stream object of the class Scanner
Use the methods such as next, nextLine, nextInt, nextLong, nextFloat, nextDouble, and hasNext
Java Programming: Program Design Including Data Structures

32. Input (continued) import java.util.*;//
public class HolaAmigo { /* my second JAVA program - making friends */
static Scanner Console = new Scanner(System.in); public static void main(String[] argv) {
String myLine;
System.out.println ("Enter your name");
myLine = Console.nextLine();
System.out.println("Hola amigo " + myLine + ", como estas?"); } }
Java Programming: Program Design Including Data Structures

33. Input (continued) Example 2-16
static Scanner console = new Scanner(System.in);
Example 2-16
int feet;
int inches;
Suppose the input is
23 7
feet = console.nextInt(); //Line 1
inches = console.nextInt(); //Line 2
Java Programming: Program Design Including Data Structures

34. Increment and Decrement Operators
++ increments the value of its operand by 1
-- decrements the value of its operand by 1
Syntax:
Pre-increment: ++variable
Post-increment: variable++
Pre-decrement: --variable
Post-decrement: variable--
Java Programming: Program Design Including Data Structures

35. Increment and Decrement Operators
import java.util.*; public class PlusPlus { /* quick demo PRE/POST incrementation ++ operator */ static Scanner Console = new Scanner(System.in); public static void main(String[] argv) { //PRE incrementation int n = 10; System.out.println ("n is: " + n); System.out.println ("++n is: " + (++n)); System.out.println ("n is: " + n); //POST incrementation n = 20; System.out.println ("n is: " + n); System.out.println ("n++ is: " + (n++)); System.out.println ("n is: " + n); } }
n is: 10
++n is: 11
n is: 11
n is: 20
n++ is: 20
n is: 21
Java Programming: Program Design Including Data Structures

36. Strings and the Operator +
Operator + can be used to concatenate two strings, or a string and a numeric value or character
Example 2-20
String str;
int num1, num2;
num1 = 12;
num2 = 26;
str = "The sum = " + num1 + num2;
After this statement executes, the string assigned to str is:
"The sum = 1226";
Java Programming: Program Design Including Data Structures

37. Strings and the Operator + (continued)
Consider the following statement:
str = "The sum = " + (num1 + num2);
Because of parentheses, first evaluate num1+num2
Because num1 and num2 are both int variables, (num1 + num2) = ( ) = 38
After this statement executes, the string assigned to str is: "The sum = 38";
Java Programming: Program Design Including Data Structures

38. Output Standard output object is System.out Methods: Syntax:
print
println
Syntax:
System.out.print(stringExp);
System.out.println(stringExp);
System.out.println();
Java Programming: Program Design Including Data Structures

39. Commonly Used Escape Sequences
Java Programming: Program Design Including Data Structures

40. Packages, Classes, Methods, and the import Statement
Package: A collection of related classes
Class: Consists of methods
Method: Designed to accomplish a specific task
Java Programming: Program Design Including Data Structures

41. import Statement Import the components of a package into a program
Reserved word
import java.io.*;
Imports the (components of the) package java.io into the program
Primitive data types and the class String:
Part of the Java language
Don’t need to be imported
Java Programming: Program Design Including Data Structures

42. Creating a Java Application Program
Syntax of a class:
Syntax of the main method:
Java Programming: Program Design Including Data Structures

43. Programming Style and Form
Know common syntax errors and rules
Use blanks appropriately
Use a semicolon as a statement terminator
Important to have well-documented code
Good practice to follow traditional rules for naming identifiers
Java Programming: Program Design Including Data Structures

44. More on Assignment Statements
Expression
variable = variable * (expression);
is equivalent to:
variable *= expression;
Similarly,
variable = variable + (expression);
variable += expression;
Java Programming: Program Design Including Data Structures

45. Programming Examples Convert Length program: Make Change program:
Input: Length in feet and inches
Output: Equivalent length in centimeters
Make Change program:
Input: Change in cents
Output: Equivalent change in half-dollars, quarters, dimes, nickels, and pennies
Java Programming: Program Design Including Data Structures

46. Programming Examples
import java.util.*; // // Convert Length program: //
public class EnglishDistance { // converting from metric to English dist.
static Scanner Console = new Scanner(System.in); public static void main(String[] argv) {
final double INC2CM = 2.54; double meters = 1.90; //TODO: try to enter the meters value via keyboard
int feet; int inches; inches = (int) ((100*meters) / 2.54); feet = (int) (inches / 12); inches = inches - (12*feet); System.out.println("meters " + meters ); System.out.println("feet " + feet); System.out.println("inches " + inches); } }
Java Programming: Program Design Including Data Structures

47. Chapter Summary Basic elements of a Java program include:
The main method
Reserved words
Special symbols
Identifiers
Data types
Expressions
Input
Output
Statements
Java Programming: Program Design Including Data Structures

48. Chapter Summary (continued)
To create a Java application, you must understand:
Syntax rules
Semantic rules
How to manipulate strings and numbers
How to declare variables and named constants
How to receive input and display output
Good programming style and form
Java Programming: Program Design Including Data Structures

49. Homework Page 109. Problem 9. Due on Wed. Sep. 12.
Exam 1. Mon. Sept 10. Chapters 1, 2.
Java Programming: Program Design Including Data Structures