Introduction to Programming

1
Introduction to Programming
CIS 202September 14, 2007

• David Goldschmidt, Ph.D.
• Computer Science
• The College of Saint Rose

2
Representing Characters in Java

• Characters (e.g. letters, digits, symbols) are
  represented using the char data type

char c, d, e c 4 d u e
! System.out.print(c) System.out.print(d) Sy
stem.out.print(e)
3
ASCII Unicode Characters

• Character data types are encoded as numbers
• Java uses two
  bytes to store
  
  characters as
  
  Unicode

4
Character Strings (i)

• A group of characters is called a character
  string
• String literals are enclosed in double quotation
  marks
• The String class in Java allows you to create
  character string variables

System.out.print("This is a string")
String s1 "This is a string"
5
Character Strings (ii)

• In Java, String objects are similar to variables

String s1 "This is a string"
6
Character Strings (iii)

• We can use print and println to display String
  objects in Java

String firstName "Dave" String lastName
"Goldschmidt" System.out.print("Hello,
") System.out.println(firstName) System.out.pri
nt("Bye Dr. ") System.out.println(lastName)
7
The String Class Methods (i)

• Once we have a String object created, we can use
  various methods of the String class
• Determine the length of a String

String firstName "Dave" String lastName
"Goldschmidt" int len lastName.length() Syste
m.out.print("Your name has ") System.out.println(
len " letters.")
8
The String Class Methods (ii)

• Once we have a String object created, we can use
  various methods of the String class
• Convert a String to uppercase or lowercase

String s "Java is cool" System.out.println(s.to
UpperCase()) String lower s.toLowerCase() Sys
tem.out.println(lower)
9
The String Class Methods (iii)

• Once we have a String object created, we can use
  various methods of the String class
• Obtain individual characters from the String

String s "Java is cool" char firstLetter
s.charAt(0) char thirdLetter
s.charAt(2) System.out.print(firstLetter) Syste
m.out.println(thirdLetter)
10
Reading Keyboard Input (i)

• A running Java program can have both output
  (System.out) and input (System.in)

Java Program Execution
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Reading Keyboard Input (ii)

• To read input from the keyboard, we use Javas
  Scanner class
• Create a Scanner object associated with System.in

Scanner keyboard new Scanner(System.in)
12
Reading Keyboard Input (iii)

• Once created, use the Scanner object to read
  keyboard input

Scanner keyboard new Scanner(System.in) System
.out.println("Whats your name?") String name
keyboard.nextLine() System.out.println("How old
are you?") int age keyboard.nextInt()
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Reading Keyboard Input (iv)

• To use the Scanner class, we need to import in
  the class from the java.util package

import java.util.Scanner public class
NameGame public static void main(String
args) ...
14
Move on to Chapter 3

• Were done with Chapters 1 and 2
• Start reading Chapter 3
• And dont forget tocomplete Homework 1