1. Introduction to Java
Viska Mutiawani, M.Sc

2. Java: History
Computers of the past

3. Java: History (2)
The invention of the microprocessor revolutionized computers
Intel microprocessor
Commodore Pet microcomputer

4. Java: History (3)
It was believed that the logical next step for microprocessors was to have them run intelligent consumer electronics

5. Java History (4)
Sun Microsystems funded an internal research project “Green” to investigate this opportunity.
Result: A programming language called “Oak”

6. Java History (5)
Problem: There was already a programming language called Oak.
The “Green” team met at a local coffee shop to come up with another name...
Java!

7. Java: History (6) The concept of intelligent devices didn’t catch on.
Project Green and work on the Java language was nearly canceled.

8. Java: History (7)
The popularity of the Internet resulted in Sun’s re- focusing of Java on computers.
Prior to the advent of Java, web pages allowed you to download only text and images.
Your computer at home running a web browser
Server containing a
web page
Images and text get downloaded
User clicks on a link

9. Java Applet downloaded
Java: History (8)
Java enabled web browsers allowed for the downloading of programs (Applets).
Java is still used in this context today:
Facebook (older version)
Hotmail (older version)
Your computer at home running a web browser
Server containing a web page
Java Applet downloaded
User clicks on a link
Java version of the Game of Life:
Online checkers:

10. What is java? Developed by Sun Microsystems (James Gosling)
A general-purpose object-oriented language
Based on C/C++
Designed for easy Web/Internet applications
Widespread acceptance

11. Java: Write Once, Run Anywhere
Consequence of Java’s history: platform-independence
Click on link to Applet
Byte code is downloaded
Mac user running Safari
Web page stored on Unix server
Virtual machine translates byte code to
native Mac code and the Applet is run
Windows user running Internet Explorer
Byte code (part of web page)

12. Java: Write Once, Run Anywhere
Consequence of Java’s history: platform-independent
Mac user running Safari
Web page stored on Unix server
Click on link to Applet
Byte code is downloaded
Windows user running Internet Explorer
Virtual machine translates byte code to
native Windows code and the Applet is run

13. Java: Write Once, Run Anywhere (2)
But Java can also create standard (non- web based) programs
Dungeon Master (Java version)
Kung Fu Panda 2: THQ
Examples of mobile Java games:

14. Java: Write Once, Run Anywhere (3)
Java has been used by large and reputable companies to create serious stand-alone applications.
Example:
Eclipse1: started as a programming environment created by IBM for developing Java programs. The program Eclipse was itself written in Java.
1 For more information:

15. Compiled Programs With Different Operating Systems
Windows compiler
Executable (Windows)
Computer program
Mac OS compiler
Executable (Mac)
UNIX compiler
Executable (UNIX)

16. A High Level View Of Translating/Executing Java Programs
Stage 1: Compilation
Java program
Filename.java
Java bytecode (generic binary)
Filename.class
Java compiler (javac)

17. A High Level View Of Translating/Executing Java Programs (2)
Stage 2: Interpreting and executing the byte code
Machine language instruction (UNIX)
Machine language instruction (Windows)
Machine language instruction (Apple)
Java bytecode (generic binary)
Filename.class
Java interpreter (java)

18. Java Features (1) Simple Object oriented
fixes some clumsy features of C++
no pointers
automatic garbage collection
rich pre-defined class library
Object oriented
focus on the data (objects) and methods manipulating the data
all functions are associated with objects
almost all datatypes are objects (files, strings, etc.)
potentially better code organization and reuse

19. Java Features (2) Interpreted Portable
java compiler generate byte-codes, not native machine code
the compiled byte-codes are platform-independent
java bytecodes are translated on the fly to machine readable instructions in runtime (Java Virtual Machine)
Portable
same application runs on all platforms
the sizes of the primitive data types are always the same
the libraries define portable interfaces

20. Java Features (3) Reliable Secure
extensive compile-time and runtime error checking
no pointers but real arrays. Memory corruptions or unauthorized memory accesses are impossible
automatic garbage collection tracks objects usage over time
Secure
usage in networked environments requires more security
memory allocation model is a major defense
access restrictions are forced (private, public)

21. Java Features (4) Multithreaded Dynamic
multiple concurrent threads of executions can run simultaneously
utilizes a sophisticated set of synchronization primitives (based on monitors and condition variables paradigm) to achieve this
Dynamic
java is designed to adapt to evolving environment
libraries can freely add new methods and instance variables without any effect on their clients
interfaces promote flexibility and reusability in code by specifying a set of methods an object can perform, but leaves open how these methods should be implemented
can check the class type in runtime

22. Java Disadvantages Slower than compiled language such as C
an experiment in 1999 showed that Java was 3 or 4 times slower than C or C++
title of the article: “Comparing Java vs. C/C++ Efficiency Issues to Interpersonal Issues” (Lutz Prechelt)
adequate for all but the most time-intensive programs

23. Which Java?

24. Which Java?
Java Platform, Standard Edition (Java SE) lets you develop and deploy Java applications ondesktops and servers, as well as in today's demanding embedded environments. Java offers the rich user interface, performance, versatility, portability, and security that today’s applicationsrequire.

25. Which Java?
Java 8+ (current is 8u20 version) JDK (Java Development Kit), Standard Edition includes:
JDK (Java development kit) – for developing Java software (creating Java programs.)
JRE (Java Runtime environment) – only good for running pre-created Java programs.
Java Plug-in – a special version of the JRE designed to run through web browsers.

26. Install JavaTM 2 Platform on your machine
Can be installed on different platforms:
Unix/Linux
Windows
Mac OS
Follow the on-line instructions:

27. Smallest Compilable And Executable Java Program
The name of the online example is: Smallest.java (Important note: file name matches the word after the keyword ‘class’)
public class Smallest {
public static void main (String[] args) }

28. Creating, Compiling And Running Java Programs On The Computer Science Network
Type it in with the text editor of your choice
filename.java
(Unix file)
Java program
javac
Java compiler
To compile the program at the command line type "javac filename.java"
Java byte code
filename.class
(UNIX file)
java
Java Interpreter
To run the interpreter, at the command line type "java filename"

29. Compiling The Smallest Java Program
public class Smallest {
public static void main (String[] args) }
Smallest.java
Type “javac Smallest.java”
javac
(Java byte code)
: :
Smallest.class

30. Running The Smallest Java Program
(Java byte code)
: :
Smallest.class
java
Type “java Smallest”
(Platform/Operating specific binary
: :

31. Running The Java Compiler At Home
After installing Java you will need to indicate to the operating system where the java compiler has been installed (‘setting the path’).
For details of how to set your path variable for your particular operating system try the Sun or Java website.
Example of how to set the path in Windows:

32. Getting Started: (1) (1) Create the source file:
open a text editor, type in the code which defines a class (HelloWorldApp) and then save it in a file (HelloWorldApp.java)
file and class name are case sensitive and must be matched exactly (except the .java part)
Example Code: HelloWorldApp.java
/**
* The HelloWorldApp class implements an application
* that displays "Hello World!" to the standard output */
public class HelloWorldApp {
public static void main(String[] args) {
// Display "Hello World!"
System.out.println("Hello World!"); }
Java is CASE SENSITIVE!

33. C:\j2sdk1.4.2_09\bin\javac HelloWorldApp.java
Getting Started: (2)
(2) Compile the program:
compile HelloWorldApp.java by using the following command:
javac HelloWorldApp.java
it generates a file named HelloWorldApp.class
‘javac’ is not recognized as an internal or external command, operable program or hatch file.
javac: Command not found
if you see one of these errors, you have two choices:
1) specify the full path in which the javac program locates every time. For example:
C:\j2sdk1.4.2_09\bin\javac HelloWorldApp.java
2) set the PATH environment variable

34. Getting Started: (3) (3) Run the program: run the code through:
java HelloWorldApp
Note that the command is java, not javac, and you refer to
HelloWorldApp, not HelloWorldApp.java or HelloWorldApp.class
Exception in thread "main" java.lang.NoClassDefFoundError:
HelloWorldApp
if you see this error, you may need to set the environment variable CLASSPATH.

35. Documentation / Comments
Multi-line documentation
/* Start of documentation
End of documentation */
Documentation for a single line
//Everything until the end of the line is a comment

36. Doc secara otomatis
Komentar yang dimulai dengan /** dan berakhir dengan */ akan menghasilkan doc secara otomatis.
javadoc yang disediakan dalam java akan melakukan proses searching terhadap /** terhadap file program, jika ketemu maka akan dibuat file HTML untuk dokumentasi
Contoh doc versi Java

37. Review: What Should You Document?
Program (or that portion of the program) author
What does the program as a while do e.g., tax program.
What are the specific features of the program e.g., it calculates personal or small business tax.
What are it’s limitations e.g., it only follows Canadian tax laws and cannot be used in the US. In Canada it doesn’t calculate taxes for organizations with yearly gross earnings over $1 billion.
What is the version of the program
If you don’t use numbers for the different versions of your program then consider using dates (tie versions with program features).

38. Important Note Each Java instruction must be followed by a semi-colon!
General format
Instruction1;
Instruction2;
Instruction3;
: :
Examples
int num = 0;
System.out.println(num);
: :

39. Java Output Format: Examples
System.out.print(<string or variable name one> + <string or variable name two>..); OR
System.out.println(<string or variable name one> + <string or variable name two>..);
Examples
public class OutputExample1 {
public static void main (String [] args)
int num = 123; // More on this shortly
System.out.println("Good-night gracie!");
System.out.print(num);
System.out.println("num="+num); }

40. Output : Some Escape Sequences For Formatting
Description \t
Horizontal tab \r
Carriage return \n
New line \”
Double quote \\
Backslash

41. Example Formatting Codes
Example: FormattingExample.java
public class FormattingExample {
public static void main (String [] args)
System.out.print("lol\tz\n");
System.out.println("hello\rworld");
System.out.println("\"Geek\" talk slash (\\) com"); }

42. Language basics Data types Variables 8 primitive types:
boolean, byte, short, int, long, float, double, char
Class types, either provided by Java, or made by programmers
String, Integer, Array, Frame, Object, Person, Animal, …
Array types
Variables
dataType identifier [ = Expression]:
Example variable declarations and initializations:
int x; x=5;
boolean b = true;
Frame win = new Frame();
String x = “how are you?”;
int[] intArray;
intArray = new int[2];
intArray[0] = 12;
intArray[1] = 6;
Person pArray = new Person[10];

43. Variables Variables must be declared before they can be used.
Variable declaration:
Creates a variable in memory.
Specify the name of the variable as well as the type of information that it will store.
E.g. int num;
Although requiring variables to be explicitly declared appears to be an unnecessary chore it can actually be useful for minimizing insidious logic errors.
Using variables
Only after a variable has been declared can it be used.
E.g., num = 12;

44. Declaring Variables: Syntax
Format:
<type of information> <name of variable>;
Example:
char myFirstInitial;
Variables can be initialized (set to a starting value) as they’re declared:
char myFirstInitial = ‘j’;
int age = 30;

45. Some Built-In Types Of Variables In Java
Description
byte
8 bit signed integer
short
16 but signed integer
int
32 bit signed integer
long
64 bit signed integer
float
32 bit signed real number
double
64 bit signed real number
char
16 bit Unicode character (ASCII and beyond)
boolean
1 bit true or false value
String
A sequence of characters between double quotes ("")

46. Location Of Variable Declarations
public class <name of class> {
public static void main (String[] args)
// Local variable declarations occur here
<< Program statements >>
: : }

47. Style Hint: Initializing Variables
Always initialize your variables prior to using them!
Do this whether it is syntactically required or not.
Example how not to approach:
public class OutputExample1 {
public static void main (String [] args)
int num;
System.out.print(num); }
OutputExample1.java:7: error: variable num might not have been initialized
System.out.print(num); ^

48. Boolean Tipe data boolean hanya bernilai true dan false.
Digunakan untuk menguji ungkapan, dapat digunakan pada seleksi dan looping
Dalam bahasa C tidak ada jenis data boolean. Biasanya 0 dan 1 (atau bukan nol) digunakan untuk mewakili nilai benar dan salah
Dalam C++, jenis data bool digunakan

49. Boolean: contoh lapar hanya mungkin bernilai true/false.
boolean lapar;
lapar = true;
while(lapar){
System.out.println(“Kasih Makan dong...”);
lapar = false; }
lapar hanya mungkin bernilai true/false.
Looping while akan berhenti apabila nilai lapar bernilai false.

50. Explicit Casting
Ada kalanya kita ingin menganggap variable bernilai double sebagai integer
Contoh:
double hasilBagi = ;
int hasil = (int) hasilBagi;
Nilai hasil adalah 20. Artinya terdapat data yang akan hilang.

51. Rounding/Pembulatan
Dalam Java, kita bisa membulatkan suatu nilai double/float kepada integer terdekat, kita bisa menggunakan method Math.round
double nilaiRata2 = ;
int hasilPembulatan=(int) Math.round(nilaiRata2);
Nilai hasilPembulatan ialah 21 setelah dibulatkan.
Penggunaan casting (int) masih diperlukan karena nilai yang dikembalikan oleh method round berjenis long.
Kita perlu tukarkan long kepada int, menggunakan casting.

52. Implicit Casting
Java membolehkan penukaran hasil suatu tipe data tanpa menggunakan proses casting mengikuti urutan berikut:
byte  short  int  long  float  double
char  int
**(dibaca: byte boleh ditukar kepada short
short boleh ditukar kepada int.. dll)
int x = 10; // occupies 4 bytes
double y = x; // occupies 8 bytes
System.out.println(y); // prints 10.0

53. Java Constants
Reminder: constants are like variables in that they have a name and store a certain type of information but unlike variables they CANNOT change.
Format:
final <constant type> <CONSTANT NAME> = <value>;
Example:
final int SIZE = 100;

54. Location Of Constant Declarations
public class <name of class> {
public static void main (String[] args)
// Local constant declarations occur here (more later)
// Local variable declarations
< Program statements >>
: : }

55. Why Use Constants?
They make your program easier to read and understand
populationChange = ( – ) * currentPopulation;
Vs.
final float BIRTH_RATE = 17.58;
final float MORTALITY_RATE = ;
int currentPopulation = ;
populationChange = (BIRTH_RATE - MORTALITY_RATE) * currentPopulation;

56. Why Use Constants? (2)
It can make your program easier to maintain (update with changes).
If the constant is referred to several times throughout the program, changing the value of the constant once will change it throughout the program.

57. Why Use Constants? (3) final float BIRTH_RATE = 0.1758;
final float MORTALITY_RATE = ;
float populationChange = 0;
float currentPopulation = ;
populationChange = (BIRTH_RATE - MORTALITY_RATE) * currentPopulation;
if (populationChange > 0)
System.out.println("Increase“)
System.out.println("Birth rate:“+ BIRTH_RATE + " Mortality rate:“ +
MORTALITY_RATE, " + Population change:“ + populationChange);
else if (populationChange < 0)
System.out.println("Decrease“);
System.out.println("Birth rate:“+BIRTH_RATE, “+Mortality rate:“+ MORTALITY_RATE
+"Population change:“+populationChange);
else
System.out.print("No change“);
System.out.print("Birth rate:“+BIRTH_RATE, “+Mortality rate:“+ MORTALITY_RATE+
"Population change:“+populationChange);

58. Why Use Constants? (4)
One change in the initialization of the constant changes all references to that constant.
final float BIRTH_RATE = 0.5;
final float MORTALITY_RATE = ;
float populationChange = 0;
float currentPopulation = ;
populationChange = (BIRTH_RATE - MORTALITY_RATE) * currentPopulation;
if (populationChange > 0)
System.out.println("Increase“)
System.out.println("Birth rate:“+ BIRTH_RATE + " Mortality rate:“ +
MORTALITY_RATE, " + Population change:“ + populationChange);
else if (populationChange < 0)
System.out.println("Decrease“);
System.out.println("Birth rate:“+BIRTH_RATE, “+Mortality rate:“+ MORTALITY_RATE
+"Population change:“+populationChange);
else
System.out.print("No change“);
System.out.print("Birth rate:“+BIRTH_RATE, “+Mortality rate:“+ MORTALITY_RATE+
"Population change:“+populationChange);

59. Variable Naming Conventions In Java
Compiler requirements
Can’t be a keyword nor can the names of the special constants: true, false or null be used
Can be any combination of letters, numbers, underscore or dollar sign (first character must be a letter or underscore)
Common stylistic conventions
The name should describe the purpose of the variable
Avoid using the dollar sign
With single word variable names, all characters are lower case
e.g., double grades;
Multiple words are separated by capitalizing the first letter of each word except for the first word
e.g., String firstName = “James”;

60. Java Keywords abstract boolean break byte case catch char class const
continue
default do
double
else
extends
final
finally
float
for
goto if
implements
import
instanceof
int
interface
long
native
new
package
private
protected
public
return
short
static
super
switch
synchronized
this
throw
throws
transient
try
void
volatile
while

61. Operator **Sama seperti dalam C Operator dasar: Contoh: (++ dan –-)
+, -, /, *, %
Contoh:
bil += 5; setara dengan bil = bil + 5;
(++ dan –-)
int i= 1;
int x = i; //nilai x menjadi 3
//nilai i menjadi 2

62. Hubungan **Sama seperti dalam C Operator dasar: Apa bedanya?
==, !=, <, >, <=, >=
Apa bedanya?
bil = 0;
if(bil == 0)

63. Operator logik **Sama seperti dalam C Operator dasar: && : DAN
|| : ATAU
! : BUKAN

64. Common Java Operators / Operator Precedence
Precedence level
Operator
Description
Associativity 1
expression++
expression--
Post-increment
Post-decrement
Right to left 2
++expression
--expression + - ! ~
(type)
Pre-increment
Pre-decrement
Unary plus
Unary minus
Logical negation
Bitwise complement
Cast

65. Common Java Operators / Operator Precedence
Precedence level
Operator
Description
Associativity 3 * / %
Multiplication
Division
Remainder/modulus
Left to right 4 + -
Addition or String concatenation
Subtraction 5
<<
>>
Left bitwise shift
Right bitwise shift

66. Common Java Operators / Operator Precedence
Precedence level
Operator
Description
Associativity 6
<
<=
>
>=
Less than
Less than, equal to
Greater than
Greater than, equal to
Left to right 7
= = !=
Equal to
Not equal to 8
&
Bitwise AND 9 ^
Bitwise exclusive OR

67. Common Java Operators / Operator Precedence
Precedence level
Operator
Description
Associativity 10 |
Bitwise OR
Left to right 11
&&
Logical AND 12 ||
Logical OR

68. Common Java Operators / Operator Precedence
Precedence level
Operator
Description
Associativity 13 = += -= *= /= %=
&= ^= |=
<<=
>>=
Assignment
Add, assignment
Subtract, assignment
Multiply, assignment
Division, assignment
Remainder, assignment
Bitwise AND, assignment
Bitwise XOR, assignment
Bitwise OR, assignment
Left shift, assignment
Right shift, assignment
Right to left

69. Post/Pre Operators The name of the example is: Order1.java
public class Order1 {
public static void main (String [] args)
int num = 5;
System.out.println(num);
num++;
++num;
System.out.println(++num);
System.out.println(num++); }

70. Post/Pre Operators (2) The name of the example is: Order2.java
public class Order2 {
public static void main (String [] args)
int num1;
int num2;
num1 = 5;
num2 = ++num1 * num1++;
System.out.println("num1=" + num1);
System.out.println("num2=" + num2); }

71. Unary Operator/Order/Associativity
The name of the example: Unary_Order3.java
public class Unary_Order3.java {
public static void main (String [] args)
int num = 5;
float fl;
System.out.println(num);
num = num * -num; }

72. Accessing Pre-Created Java Libraries
It’s accomplished by placing an ‘import’ of the appropriate library at the top of your program.
Syntax:
import <Full library name>;
Example:
import java.util.Scanner;

73. Getting Text Input
You can use the pre-written methods (functions) in the Scanner class.
General structure:
import java.util.Scanner;
main (String [] args) {
Scanner <name of scanner> = new Scanner (System.in);
<variable> = <name of scanner> .<method> (); }
Creating a scanner object (something that can scan user input)
Using the capability of the scanner object (actually getting user input)

74. Getting Text Input (2) The name of the example: MyInput.java
import java.util.Scanner;
public class MyInput {
public static void main (String [] args)
String str1;
int num1;
Scanner in = new Scanner (System.in);
System.out.print ("Type in an integer: ");
num1 = in.nextInt ();
System.out.print ("Type in a line: ");
in.nextLine ();
str1 = in.nextLine ();
System.out.println ("num1:" +num1 +"\t str1:" + str1); }

75. Useful Methods Of Class Scanner1
nextInt ()
nextLong ()
nextFloat ()
nextDouble ()
nextLine ();
1 Online documentation: docs.oracle.com/javase/7/docs/api/

76. Reading A Single Character
Text menu driven programs may require this capability.
Example:
GAME OPTIONS
(a)dd a new player
(l)oad a saved game
(s)ave game
(q)uit game
There’s different ways of handling this problem but one approach is to extract the first character from the string.
Partial example:
String s = "boo“;
System.out.println(s.charAt(0));

77. Reading A Single Character
Name of the (more complete example): MyInputChar.java
import java.util.Scanner;
public class MyInputChar {
public static void main (String [] args)
final int FIRST = 0;
String selection;
Scanner in = new Scanner (System.in);
System.out.println("GAME OPTIONS");
System.out.println("(a)dd a new player");
System.out.println("(l)oad a saved game");
System.out.println("(s)ave game");
System.out.println("(q)uit game");
System.out.print("Enter your selection: ");

78. Reading A Single Character (2)
selection = in.nextLine ();
System.out.println ("Selection: " + selection.charAt(FIRST)); }

79. Decision Making In Java
Java decision making constructs if
if, else
if, else-if
switch

80. Decision Making: Logical Operators
Logical Operation
Java
AND
&& OR ||
NOT !

81. Decision Making: If Format: Example: if (Boolean Expression)
Body
Example:
if (x != y)
System.out.println("X and Y are not equal");
if ((x > 0) && (y > 0)) {
System.out.println("X and Y are positive"); }
Indenting the body of the branch is an important stylistic requirement of Java.
What distinguishes the body is either:
A semi colon (single statement branch)
Braces (a body that consists of multiple statements)

82. Decision Making: If, Else
Format:
if (Boolean expression)
Body of if
else
Body of else
Example:
if (x < 0)
System.out.println("X is negative");
System.out.println("X is non-negative");

83. Example Program: If-Else
Name of the example: BranchingExample1.java
import java.util.Scanner;
public class BranchingExample1 {
public static void main (String [] args)
Scanner in = new Scanner(System.in);
final int WINNING_NUMBER = ;
int playerNumber = -1;
System.out.print("Enter ticket number: ");
playerNumber = in.nextInt();
if (playerNumber == WINNING_NUMBER)
System.out.println("You're a winner!");
else
System.out.println("Try again."); }

84. If, Else-If Format: if (Boolean expression) Body of if
else if (Boolean expression)
Body of first else-if
: : :
Body of last else-if
else
Body of else

85. If, Else-If (2) Name of the example: BranchingExample.java
import java.util.Scanner;
public class BranchingExample2 {
public static void main (String [] args)
Scanner in = new Scanner(System.in);
int gpa = -1;
System.out.print("Enter letter grade: ");
gpa = in.nextInt();

86. If, Else-If (3) if (gpa == 4) System.out.println("A");
else if (gpa == 3)
System.out.println("B");
else if (gpa == 2)
System.out.println("C");
else if (gpa == 1)
System.out.println("D");
else if (gpa == 0)
System.out.println("F");
else
System.out.println("Invalid letter grade"); }

87. Branching: Common Mistakes
Recall that for single bodies: what lies between the closing bracket of the Boolean expression and the next semi-colon is the body.
if (Boolean Expression)
instruction;
if (Boolean Expression) instruction;
instruction1;
Instruction2;
body
body
body

88. Branching: Now What Happens???
if (Boolean Expression):
instruction1;
instruction2;

89. Alternative To Multiple Else-If’s: Switch
Format (character-based switch):
switch (character variable name) {
case '<character value>':
Body
break; :
default: }
1 The type of variable in the brackets can be a byte, char, short, int or long
Important! The break is mandatory to separate Boolean expressions (must be used in all but the last)

90. Alternative To Multiple Else-If’s: Switch (2)
Format (integer based switch):
switch (integer variable name) {
case <integer value>:
Body
break; :
default: }
1 The type of variable in the brackets can be a byte, char, short, int or long

91. Switch: When To Use/When Not To Use
Benefit (when to use):
It may produce simpler code than using an if- elseif (e.g., if there are multiple compound conditions)

92. Switch: When To Use/When Not To Use (2)
Name of the example: SwitchExample.java
import java.util.Scanner;
public class SwitchExample {
public static void main (String [] args)
final int FIRST = 0;
String line;
char letter;
int gpa;
Scanner in = new Scanner (System.in);
System.out.print("Enter letter grade: ");

93. Switch: When To Use/When Not To Use (3)
line = in.nextLine ();
letter = line.charAt(FIRST);
switch (letter) {
case 'A':
case 'a':
gpa = 4;
break;
case 'B':
case 'b':
gpa = 3;
case 'C':
case 'c':
gpa = 2;

94. Switch: When To Use/When Not To Use (4)
case 'D':
case 'd':
gpa = 1;
break;
case 'F':
case 'f':
gpa = 0;
default:
gpa = -1; }
System.out.println("Letter grade: " + letter);
System.out.println("Grade point: " + gpa);

95. Switch: When To Use/When Not To Use (5)
When a switch can’t be used:
For data types other than characters or integers
Boolean expressions that aren’t mutually exclusive:
As shown a switch can replace an ‘if-elseif’ construct
A switch cannot replace a series of ‘if’ branches).
Example when not to use a switch:
if (x > 0)
System.out.print(“X coordinate right of the origin”);
If (y > 0)
System.out.print(“Y coordinate above the origin”);
Example of when not to use a switch:
String name = in.readLine()
switch (name) { }

96. Switch Example: Modified
What happens if all the ‘break’ instructions have been removed?

97. STRUKTUR KAWALAN STRUKTUR PEMILIHAN STRUKTUR PENGULANGAN if-else
switch-break
STRUKTUR PENGULANGAN
while
do-while
for

98. STRUKTUR PEMILIHAN if-else Contoh:
if (ungkapan)
kenyataan
Contoh:
if (skorPelajar >= 60)
System.out.println(“LULUS”);
Sintaksnya sama dengan C, kecuali dalam Java, ungkapan mesti bernilai boolean (true or false).
Oleh itu penggalan berikut tidak dibenarkan dalam Java:
int bilangan =10;
if(bilangan)
System.out.print(“*”);

99. STRUKTUR PEMILIHAN switch-case **sintaksnya sama seperti C
Hanya boleh jenis integer dan aksara: byte, char, short, int atau long
int pilihan =1;
switch(pilihan){
case 1: …
break;
case 2: ..
default: … }

100. STRUKTUR PENGULANGAN while, do-while dan for
**sintaksnya sama seperti C
Buatkan program Java dengan menggunakan while dan do-while bagi pseudokod di bawah:
lapar = benar
Selagi lapar benar
tampilkan “beri makanan”
lapar = false
Tamat selagi
boolean lapar = benar;
while(lapar){
System.out.print(“berikan”);
lapar = false; }
do{
}while(lapar);

101. Loops
Java Pre-test loops
For
While
Java Post-test loop
Do-while

102. While Loops Format: Example: while (Boolean expression) Body
int i = 1;
while (i <= 4) {
// Call function
createNewPlayer();
i = i + 1; }

103. For Loops Format: Example:
for (initialization; Boolean expression; update control)
Body
Example:
for (i = 1; i <= 4; i++) {
// Call function
createNewPlayer();
i = i + 1; }

104. Post-Test Loop: Do-While
Recall: Post-test loops evaluate the Boolean expression after the body of the loop has executed.
This means that post test loops will execute one or more times.
Pre-test loops generally execute zero or more times.

105. Do-While Loops Format: Example: do Body while (Boolean expression);
char ch = 'A'; {
System.out.println(ch);
ch++; }
while (ch <= 'K');

106. Contrasting Pre Vs. Post Test Loops
Although slightly more work to implement the while loop is the most powerful type of loop.
Program capabilities that are implemented with either a ‘for’ or ‘do-while’ loop can be implemented with a while loop.
Implementing a post test loop requires that the loop control be primed correctly (set to a value such that the Boolean expression will evaluate to true the first it’s checked).

107. Example: Post-Test Implementation
Name of the example: PostTestExample.java
public class PostTestExample {
public static void main (String [] args)
final int FIRST = 0;
Scanner in = new Scanner(System.in);
char answer;
String temp; do
System.out.println("JT's note: Pretend that we play our game");
System.out.print("Play again? Enter 'q' to quit: ");
temp = in.nextLine();
answer = temp.charAt(FIRST);
} while ((answer != 'q') && (answer != 'Q')); }

108. Example: Pre-Test Implementation
Name of the example: PreTestExample.java
public class PreTestExample {
public static void main (String [] args)
final int FIRST = 0;
Scanner in = new Scanner(System.in);
char answer = ' ';
String temp;
while ((answer != 'q') && (answer != 'Q'))
System.out.println("JT's note: Pretend that we play our game");
System.out.print("Play again? Enter 'q' to quit: ");
temp = in.nextLine();
answer = temp.charAt(FIRST); }

109. Now What Happens??? import java.util.Scanner;
public class PreTestExample {
public static void main (String [] args)
final int FIRST = 0;
Scanner in = new Scanner(System.in);
char answer = ' ';
String temp;
while ((answer != 'q') && (answer != 'Q'))
System.out.println("JT's note: Pretend that we play our game");
System.out.print("Play again? Enter 'q' to quit: ");
temp = in.nextLine();
answer = temp.charAt(FIRST); }

110. int[] tts = new int[100]; ATAU
Array
Sintaks
Tipe_data[] nama_variable = new tipe_data[ukuran];
Contoh:
int[] tts = new int[100]; ATAU
int[] tts;
tts = new int[100]; ATAU
int tts[]= new int[100];

111. Array (2) Memberi nilai kepada array:
int[] nilai = {2, 3, 4, 5};
char[] abjad= {a, b, c, d};
Kita juga bisa membuat array tanpa nama:
new int[]{2, 3, 5, 7, 11};
menyediakan satu array baru dengan
nilai-nilai tersebut. Sering dipakai untuk mengirim parameter ke method.

112. Array (3)
Digunakan apabila kita ingin mengirimkan array sebagai parameter pada method.
cetakLimaPrima(new int[] {2,3,5,7,11} );
ATAU
int[] nomPrima = {2,3,5,7,11};
cetakLimaPrima(nomPrima);

113. Array Sebagai Objek
Apabila ia dianggap sebagai objek, maka ia mempunyai atribut dan method
Atribut length
Menentukan ukuran suatu array:
nama_array.length
int nomPrima={2, 3, 5, 7, 11};
for(int i=0; i<nomPrima.length;i++)
System.out.println(nomPrima[i]);

114. Method arraycopy()
Mengcopy dari satu array ke array yang lain. Sintaksnya:
System.arraycopy(sumber,indekSumber,sasaran, indekSasaran,bil);
sumber :nama array yang hendak dicopy
indekSumber :permulaan kedudukan array yang akan di copy dari sumber
sasaran : array baru yang akan menyimpan
kandungan array sumber
indekSasaran :permulaan kedudukan pada array
sasaran untuk menyimpan nilai yang dicopy
bil : jumlah nilai yang dicopy

115. Metod arraycopy()
int[] nomGanjil ={1, 3, 5, 7, 9}; int[] nomPositif={10, 20, 30, 40, 50, 60}; System.arraycopy(nomGanjil, 1, nomPositif, 2, 3); for(int i=0; i<nomPositif.length; i++){ Sysem.out.println(“nomPositif[“ + i + “] selepas copy:” +nomPositif[i]); }
nomPositif[0] selepas copy ialah 10
nomPositif[1] selepas copy ialah 20
nomPositif[2] selepas copy ialah 3
nomPositif[3] selepas copy ialah 5
nomPositif[4] selepas copy ialah 7
nomPositif[5] selepas copy ialah 60
Copy nomGanjil kepada nomPositif
Bilangan yang hendak dicopy adalah 3, bermula dari indeks nomGanjil[1]
Nombor-nombor akan disimpan pada nomPositif bermula dari nomPositif[2]
OUTPUT

116. System.arraycopy(nomGanjil, 1, nomPositif, 2, 3);5 7 9 10 20 30 40 50
Sebelum copy 60 1 3 5 7 9 10 20 3 5 7
Selepas copy 60

117. String Berbeda dengan C, Java mempunyai kelas String.
Kita tidak perlu tipe data array char untuk menyimpan rentetan aksara.
Tipe data berjenis String akan menyimpan aksara di antara tanda “ “, termasuk ruang kosong
Contoh: String kosong=“”; //suatu rentetan kosong
String namaSaya = “Mohammad Muktasim”;

118. Operasi Terhadap String
Menggabung string
Menggunakan operator ‘+’
String judul = “OO”;
String buku = “.Java”;
String judulBuku = judul + buku;
System.out.println(judulBuku);
OUTPUT
OO.Java //tanpa spasi

119. Operasi Terhadap String
Java mengira subrentetan
bermula dari 0 hingga 4
0: kedudukan ‘P’
4: kedudukan ‘i’
Substring
Mendapatkan sebahagian daripada string yang lengkap
Metod substring() digunakan
String senikata = “Puji dan syukur kepada Ilahi”;
String s = senikata.substring(0,4);
System.out.println(“Subrentetan bernilai ”+s);
OUTPUT
Subrentetan bernilai Puji

120. Operasi Terhadap String
Panjang string
Mendapatkan panjang suatu string
Metod length() digunakan
String kata = “Salam Sejahtera”;
int panjang = kata.length(); // panjang bernilai 15
Membanding string
Menguji apakah dua string mempunyai nilai yang sama
Metod equals() digunakan
“salam”.equals(kata); // bernilai false
“Salam sejahtera”.equalIgnoreCase(kata); // bernilai true

121. Method parser Contoh: weight = Integer.parseInt(kilo);
Nilai yang berjenis String yang disimpan dalam kilo akan ditukar menjadi integer dan disimpan dalam weight
Jenis parser yang lain:
parseInt(), parseFloat(), parseLong(), parseDouble, parseShort(), parseByte().

122. Many Pre-Created Classes Have Been Created
Rule of thumb: Before writing new program code to implement the features of your program you should check to see if a class has already been written with the features that you need.
The Java API is Sun Microsystems's collection of pre-built Java classes:
docs.oracle.com/javase/7/docs/api/

123. I hear, I forget I write, I remember I do, I understand.. so.. just do it! :-)

124. Supplemental reading
Getting Started
Nuts and bolts of the Java Language
Compiling and Running a Simple Program