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Java 101: Intro to Java
Programming
Introduction
• Your Name: Manuela Grindei
• Your day job: Software Developer @ Gamesys
• Your last holiday destination: Dublin
Java 101
• Java Fundamentals
– Setting up your development environment
– Language Overview
– How Java Works
– Writing your first program
– Built-in Data Types
– Conditionals and Loops
Java 102
• Object-oriented Programming
– Classes and Objects
– Polymorphism, Inheritance and Encapsulation
– Functions and Libraries
Java 103
• Data Structures
– Arrays
– Collections
– Algorithms
Java 101: Introduction to Java
Setting up your Development
Environment
Installing Java Development Kit
• Download latest Java SE 8 JDK (not JRE) from
http://www.oracle.com/technetwork/java/javase/downloads/jdk8-
downloads-2133151.html
• For Windows,
– download the X86 version, double click the .exe file and follow the
instructions, accepting all default
• For MACs,
– check if java already installed (javac –version) and if not, download the
JDK dmg file, run it and follow the instructions.
• After installation is complete, type javac –version in the Command
window (Terminal window on MAC OS)-
– The reported version should be 1.8....
– If not, you may need to modify the system variable PATH to include the
bin directory of JDK
What is an IDE?
• IDE = Integrated Development Environment
• Makes you more productive
• Includes text editor, compiler, debugger,
context- sensitive help, works with different
Java SDKs
• Eclipse is the most widely used IDE
• Alternatives:
– IntelliJ IDEA (JetBrains)
– NetBeans (Oracle)
Installing Eclipse
• Download and install the latest Eclipse for Java
EE (32 Bit version) from
http://www.eclipse.org/downloads
• Unzip the content of the archive file you
downloaded
• To start Eclipse
– On PC, double-click on Eclipse.exe
– On Mac, double click Eclipse.app in Application
folder
Hands-on Exercise
Intelli j Setup & Demo
https://www.jetbrains.com/idea/download/
Java 101: Introduction to Java
Language Overview
Java Language History
Java Language Overview
Java Editions
• Java SE: Java Standard Edition
• Java EE: Java Enterprise Edition (a.k.a. J2EE)
– includes a set of technologies built on top of Java
SE: Servlets, JSP, JSF, EJB, JMS, et al.
• Java ME: Java Micro Edition
• Java Card for Smart Cards
• All Java programs run inside the Java Virtual
Machine (JVM)
JDK vs. JRE
• Java Development Kit (JDK) is required to
develop and compile programs
• Java Runtime Environment (JRE) is required to
run programs
• Users must have JRE installed
• Developers must have the JDK installed
• JDK includes the JRE
Java 101: Introduction to Java
How Java Works
How Java Works
Java File Structure
Java 101: Introduction to Java
Writing Your First Program
Writing Your First Java Program
• Create a new project in your IDE named Java101
• Create a HelloWorld class in the src folder inside the Java101
project as illustrated below.
Anatomy of a Java Application
Comments Class Name
Access
modifier
Function/static
method
Arguments
Compiling Your First Java Program
• Save the HelloWorld class in the IDE
• Run your program: right-clicking and selecting Run
As>Java Application
• This automatically compiles the HelloWorld.java file into
into a HelloWorld.class file
• Go to the folder you created the Java101 project on your
hard disk and open the src(eclipse) or out (Intelli j)folder.
• What do you see?
Built-in classes
Introduction to Java
Built-in Data Types
Built-in Data Types
• Data types are sets of values and operations
defined on those values
Basic Definitions
• Variable - a name that refers to a value.
• Assignment statement - associates a value
with a variable.
String Data Type
Data Type Attributes
Values sequence of characters
Typical literals “Hello”, “1 “, “*”
Operation Concatenate
Operator +
• Useful for program input and output.
String Data Type
String Data Type
• Meaning of characters depends on context.
String Data Type
Expression Value
“Hi, “ + “Bob” “Hi, Bob”
“1” + “ 2 “ + “ 1” “ 1 2 1”
“1234” + “ + “ + “99” “1234 + 99”
“1234” + “99” “123499”
Hands-on Exercise
Command Line Arguments
Exercise: Command Line Arguments
• Create the Java program below that takes a name as
command-line argument and prints “Hi <name>,
How are you?”
Integer Data Type
Data Type Attributes
Values Integers between -2^31 to +2^31-1
Typical literals 1234, -99 , 99, 0, 1000000
Operation Add subtract multiply divide remainder
Operator + - * / %
• Useful for expressing algorithms.
Integer Data Type
Expression Value Comment
5 + 3 8
5 – 3 2
5 * 3 15
5 / 3 1 no fractional part
5 % 3 2 remainder
1 / 0 run-time error
3 * 5 - 2 13 * has precedence
3 + 5 / 2 5 / has precedence
3 – 5 - 2 -4 left associative
(3-5) - 2 -4 better style
3 – (5-2) 0 unambiguous
Double Data Type
• Useful in scientific applications and floating-
point arithmetic
Data Type Attributes
Values Real numbers specified by the IEEE 754 standard
Typical literals 3.14159 6.022e23 -3.0 2.0 1.41421356237209
Operation Add subtract multiply divide
Operator + - * /
Double Data Type
Expression Value
3.141 + 0.03 3.171
3.141 – 0.03 3.111
6.02e23 / 2 3.01e23
5.0 / 2.0 1.6666666666667
10.0 % 3.141 0.577
1.0 / 0.0 Infinity
Math.sqrt(2.0) 1.4142135623730951
Java Math Library
Methods
Math.sin() Math.cos()
Math.log() Math.exp()
Math.sqrt() Math.pow()
Math.min() Math.max()
Math.abs() Math.PI
http://java.sun.com/javase/6/docs/api/java/lang/Math.html
Hands-on Exercise
Integer Operations
Exercise: Integer Operations
• Create a Java class named IntOps in the Java101
project that performs integer operations on a pair of
integers from the command line and prints the results.
Solution: Integer Operations
Boolean Data Type
• Useful to control logic and flow of a program.
Data Type Attributes
Values true or false
Typical literals true false
Operation and or not
Operator && || !
Logical operators
& (AND) | (OR)
^
(EXCLUSIVE OR)
True False True False True False
True True False True True False True
False False False True False True False
Logical operators
• & (AND): Only TRUE if both operands are TRUE
• | (OR): Only FALSE if both operands are FALSE
• ^ (EXCLUSIVE OR): Only TRUE if both operands are
DIFFERENT
Conditional & Negation operators
a !a a b a && b a || b
True False False False False False
False True False True False True
True false False True
True True true True
Boolean Comparisons
• Take operands of one type and produce an
operand of type boolean.
operation meaning true false
== equals 2 == 2 2 == 3
!= Not equals 3 != 2 2 != 2
< Less than 2 < 13 2 < 2
<= Less than or equal 2 <= 2 3 <= 2
> Greater than 13 > 2 2 > 13
>= Greater than or
equal
3 >= 2 2 >= 3
Type Conversion
• Convert from one type of data to another.
• Implicit
– no loss of precision
– with strings
• Explicit:
– cast
– method.
Type Conversion Examples
expression Expression type Expression value
“1234” + 99 String “123499”
Integer.parseInt(“123”) int 123
(int) 2.71828 int 2
Math.round(2.71828) long 3
(int) Math.round(2.71828) int 3
(int) Math.round(3.14159) int 3
11 * 0.3 double 3.3
(int) 11 * 0.3 double 3.3
11 * (int) 0.3 int 0
(int) (11 * 0.3) int 3
Hands-on Exercise
Leap Year Finder
Exercise: Leap Year Finder
• A year is a leap year if it is either divisible by 400
or divisible by 4 but not 100.
• Write a java class named LeapYear in the Java101
project that takes a numeric year as command
line argument and prints true if it’s a leap year
and false if not
Solution: Leap Year Finder
Data Types Summary
• A data type is a set of values and operations on those
values.
– String for text processing
– double, int for mathematical calculation
– boolean for decision making
• In Java, you must:
– Declare type of values.
– Convert between types when necessary
• Why do we need types?
– Type conversion must be done at some level.
– Compiler can help do it correctly.
– Example: in 1996, Ariane 5 rocket exploded after takeoff
because of bad type conversion.
Introduction to Java
Conditionals and Loops
Conditionals and Loops
• Sequence of statements that are actually
executed in a program.
• Enable us to choreograph control flow.
Conditionals
• The if statement is a common branching structure.
– Evaluate a boolean expression.
• If true, execute some statements.
• If false, execute other statements.
If Statement Example
More If Statement Examples
While Loop
• A common repetition structure.
– Evaluate a boolean expression.
– If true, execute some statements.
– Repeat.
For Loop
• Another common repetition structure.
– Execute initialization statement.
– Evaluate a boolean expression.
• If true, execute some statements.
– And then the increment statement.
– Repeat.
Anatomy of a For Loop
Loop Examples
For Loop
Hands-on Exercise
Powers of Two
Exercise: Powers of Two
• Create a new Java project in Eclipse named Pow2
• Write a java class named PowerOfTwo to print powers of 2 that are
<= 2N where N is a number passed as an argument to the program.
– Increment i from 0 to N.
– Double v each time
Solution: Power of 2
Control Flow Summary
• Sequence of statements that are actually
executed in a program.
• Conditionals and loops enable us to choreograph
the control flow.
Control flow Description Example
Straight line
programs
all statements are executed in the
order given
Conditionals certain statements are executed
depending on the values of certain
variables
If
If-else
Loops certain statements are executed
repeatedly until certain conditions
are met
while
for
do-while
Homework Exercises
Java 101: Introduction to Java
Hands-on Exercise
Random Number Generator
Exercise: Random Number Generator
• Write a java class named RandomInt to generate a
pseudo-random number between 0 and N-1 where N is
a number passed as an argument to the program
Solution: Random Number Generator
Hands-on Exercise
Array of Days
Exercise: Array of Days
• Create a java class named DayPrinter that
prints out names of the days in a week from an
array using a for-loop.
Solution: Arrays of Days
public class DayPrinter {
public static void main(String[] args) {
//initialize the array with the names of days of the
week
String[] daysOfTheWeek =
{"Sunday","Monday","Tuesday","Wednesday",
"Thuesday","Friday”,"Saturday"};
//loop through the array and print their elements to
//stdout
for (int i= 0;i < daysOfTheWeek.length;i++ ){
System.out.println(daysOfTheWeek[i]);
}
}
}
% javac DayPrinter.java
% java DayPrinter
Sunday
Monday
Tuesday
Wednesday
Thuesday
Friday
Saturday
Hands-on Exercise
Print Personal Details
Exercise: Print Personal Details
• Write a program that will print your name and
address to the console, for example:
Alex Johnson
23 Main Street
New York, NY 10001 USA
Hands-on Exercise
Sales Discount
Exercise: Sales Discount
• Create a new project in Eclipse named Sale
• Create, compile, and run the FriendsAndFamily class as illustrated below
• Debug this program in your IDE to find out how it works
Further Reading
• Java Tutorials - https://docs.oracle.com/javase/tutorial/
• Java Language Basics -
http://docs.oracle.com/javase/tutorial/java/nutsandbolts/index.html
• Eclipse IDE Workbench User Guide -
http://help.eclipse.org/kepler/index.jsp
• Intelli J IDE User Guide - https://www.jetbrains.com/idea/documentation/
• Eclipse Tutorial - http://www.vogella.com/tutorials/Eclipse/article.html

More Related Content

Java 101

  • 1. Java 101: Intro to Java Programming
  • 2. Introduction • Your Name: Manuela Grindei • Your day job: Software Developer @ Gamesys • Your last holiday destination: Dublin
  • 3. Java 101 • Java Fundamentals – Setting up your development environment – Language Overview – How Java Works – Writing your first program – Built-in Data Types – Conditionals and Loops
  • 4. Java 102 • Object-oriented Programming – Classes and Objects – Polymorphism, Inheritance and Encapsulation – Functions and Libraries
  • 5. Java 103 • Data Structures – Arrays – Collections – Algorithms
  • 6. Java 101: Introduction to Java Setting up your Development Environment
  • 7. Installing Java Development Kit • Download latest Java SE 8 JDK (not JRE) from http://www.oracle.com/technetwork/java/javase/downloads/jdk8- downloads-2133151.html • For Windows, – download the X86 version, double click the .exe file and follow the instructions, accepting all default • For MACs, – check if java already installed (javac –version) and if not, download the JDK dmg file, run it and follow the instructions. • After installation is complete, type javac –version in the Command window (Terminal window on MAC OS)- – The reported version should be 1.8.... – If not, you may need to modify the system variable PATH to include the bin directory of JDK
  • 8. What is an IDE? • IDE = Integrated Development Environment • Makes you more productive • Includes text editor, compiler, debugger, context- sensitive help, works with different Java SDKs • Eclipse is the most widely used IDE • Alternatives: – IntelliJ IDEA (JetBrains) – NetBeans (Oracle)
  • 9. Installing Eclipse • Download and install the latest Eclipse for Java EE (32 Bit version) from http://www.eclipse.org/downloads • Unzip the content of the archive file you downloaded • To start Eclipse – On PC, double-click on Eclipse.exe – On Mac, double click Eclipse.app in Application folder
  • 10. Hands-on Exercise Intelli j Setup & Demo https://www.jetbrains.com/idea/download/
  • 11. Java 101: Introduction to Java Language Overview
  • 14. Java Editions • Java SE: Java Standard Edition • Java EE: Java Enterprise Edition (a.k.a. J2EE) – includes a set of technologies built on top of Java SE: Servlets, JSP, JSF, EJB, JMS, et al. • Java ME: Java Micro Edition • Java Card for Smart Cards • All Java programs run inside the Java Virtual Machine (JVM)
  • 15. JDK vs. JRE • Java Development Kit (JDK) is required to develop and compile programs • Java Runtime Environment (JRE) is required to run programs • Users must have JRE installed • Developers must have the JDK installed • JDK includes the JRE
  • 16. Java 101: Introduction to Java How Java Works
  • 19. Java 101: Introduction to Java Writing Your First Program
  • 20. Writing Your First Java Program • Create a new project in your IDE named Java101 • Create a HelloWorld class in the src folder inside the Java101 project as illustrated below.
  • 21. Anatomy of a Java Application Comments Class Name Access modifier Function/static method Arguments
  • 22. Compiling Your First Java Program • Save the HelloWorld class in the IDE • Run your program: right-clicking and selecting Run As>Java Application • This automatically compiles the HelloWorld.java file into into a HelloWorld.class file • Go to the folder you created the Java101 project on your hard disk and open the src(eclipse) or out (Intelli j)folder. • What do you see?
  • 25. Built-in Data Types • Data types are sets of values and operations defined on those values
  • 26. Basic Definitions • Variable - a name that refers to a value. • Assignment statement - associates a value with a variable.
  • 27. String Data Type Data Type Attributes Values sequence of characters Typical literals “Hello”, “1 “, “*” Operation Concatenate Operator + • Useful for program input and output.
  • 29. String Data Type • Meaning of characters depends on context.
  • 30. String Data Type Expression Value “Hi, “ + “Bob” “Hi, Bob” “1” + “ 2 “ + “ 1” “ 1 2 1” “1234” + “ + “ + “99” “1234 + 99” “1234” + “99” “123499”
  • 32. Exercise: Command Line Arguments • Create the Java program below that takes a name as command-line argument and prints “Hi <name>, How are you?”
  • 33. Integer Data Type Data Type Attributes Values Integers between -2^31 to +2^31-1 Typical literals 1234, -99 , 99, 0, 1000000 Operation Add subtract multiply divide remainder Operator + - * / % • Useful for expressing algorithms.
  • 34. Integer Data Type Expression Value Comment 5 + 3 8 5 – 3 2 5 * 3 15 5 / 3 1 no fractional part 5 % 3 2 remainder 1 / 0 run-time error 3 * 5 - 2 13 * has precedence 3 + 5 / 2 5 / has precedence 3 – 5 - 2 -4 left associative (3-5) - 2 -4 better style 3 – (5-2) 0 unambiguous
  • 35. Double Data Type • Useful in scientific applications and floating- point arithmetic Data Type Attributes Values Real numbers specified by the IEEE 754 standard Typical literals 3.14159 6.022e23 -3.0 2.0 1.41421356237209 Operation Add subtract multiply divide Operator + - * /
  • 36. Double Data Type Expression Value 3.141 + 0.03 3.171 3.141 – 0.03 3.111 6.02e23 / 2 3.01e23 5.0 / 2.0 1.6666666666667 10.0 % 3.141 0.577 1.0 / 0.0 Infinity Math.sqrt(2.0) 1.4142135623730951
  • 37. Java Math Library Methods Math.sin() Math.cos() Math.log() Math.exp() Math.sqrt() Math.pow() Math.min() Math.max() Math.abs() Math.PI http://java.sun.com/javase/6/docs/api/java/lang/Math.html
  • 39. Exercise: Integer Operations • Create a Java class named IntOps in the Java101 project that performs integer operations on a pair of integers from the command line and prints the results.
  • 41. Boolean Data Type • Useful to control logic and flow of a program. Data Type Attributes Values true or false Typical literals true false Operation and or not Operator && || !
  • 42. Logical operators & (AND) | (OR) ^ (EXCLUSIVE OR) True False True False True False True True False True True False True False False False True False True False
  • 43. Logical operators • & (AND): Only TRUE if both operands are TRUE • | (OR): Only FALSE if both operands are FALSE • ^ (EXCLUSIVE OR): Only TRUE if both operands are DIFFERENT
  • 44. Conditional & Negation operators a !a a b a && b a || b True False False False False False False True False True False True True false False True True True true True
  • 45. Boolean Comparisons • Take operands of one type and produce an operand of type boolean. operation meaning true false == equals 2 == 2 2 == 3 != Not equals 3 != 2 2 != 2 < Less than 2 < 13 2 < 2 <= Less than or equal 2 <= 2 3 <= 2 > Greater than 13 > 2 2 > 13 >= Greater than or equal 3 >= 2 2 >= 3
  • 46. Type Conversion • Convert from one type of data to another. • Implicit – no loss of precision – with strings • Explicit: – cast – method.
  • 47. Type Conversion Examples expression Expression type Expression value “1234” + 99 String “123499” Integer.parseInt(“123”) int 123 (int) 2.71828 int 2 Math.round(2.71828) long 3 (int) Math.round(2.71828) int 3 (int) Math.round(3.14159) int 3 11 * 0.3 double 3.3 (int) 11 * 0.3 double 3.3 11 * (int) 0.3 int 0 (int) (11 * 0.3) int 3
  • 49. Exercise: Leap Year Finder • A year is a leap year if it is either divisible by 400 or divisible by 4 but not 100. • Write a java class named LeapYear in the Java101 project that takes a numeric year as command line argument and prints true if it’s a leap year and false if not
  • 51. Data Types Summary • A data type is a set of values and operations on those values. – String for text processing – double, int for mathematical calculation – boolean for decision making • In Java, you must: – Declare type of values. – Convert between types when necessary • Why do we need types? – Type conversion must be done at some level. – Compiler can help do it correctly. – Example: in 1996, Ariane 5 rocket exploded after takeoff because of bad type conversion.
  • 53. Conditionals and Loops • Sequence of statements that are actually executed in a program. • Enable us to choreograph control flow.
  • 54. Conditionals • The if statement is a common branching structure. – Evaluate a boolean expression. • If true, execute some statements. • If false, execute other statements.
  • 56. More If Statement Examples
  • 57. While Loop • A common repetition structure. – Evaluate a boolean expression. – If true, execute some statements. – Repeat.
  • 58. For Loop • Another common repetition structure. – Execute initialization statement. – Evaluate a boolean expression. • If true, execute some statements. – And then the increment statement. – Repeat.
  • 59. Anatomy of a For Loop
  • 63. Exercise: Powers of Two • Create a new Java project in Eclipse named Pow2 • Write a java class named PowerOfTwo to print powers of 2 that are <= 2N where N is a number passed as an argument to the program. – Increment i from 0 to N. – Double v each time
  • 65. Control Flow Summary • Sequence of statements that are actually executed in a program. • Conditionals and loops enable us to choreograph the control flow. Control flow Description Example Straight line programs all statements are executed in the order given Conditionals certain statements are executed depending on the values of certain variables If If-else Loops certain statements are executed repeatedly until certain conditions are met while for do-while
  • 66. Homework Exercises Java 101: Introduction to Java
  • 68. Exercise: Random Number Generator • Write a java class named RandomInt to generate a pseudo-random number between 0 and N-1 where N is a number passed as an argument to the program
  • 71. Exercise: Array of Days • Create a java class named DayPrinter that prints out names of the days in a week from an array using a for-loop.
  • 72. Solution: Arrays of Days public class DayPrinter { public static void main(String[] args) { //initialize the array with the names of days of the week String[] daysOfTheWeek = {"Sunday","Monday","Tuesday","Wednesday", "Thuesday","Friday”,"Saturday"}; //loop through the array and print their elements to //stdout for (int i= 0;i < daysOfTheWeek.length;i++ ){ System.out.println(daysOfTheWeek[i]); } } } % javac DayPrinter.java % java DayPrinter Sunday Monday Tuesday Wednesday Thuesday Friday Saturday
  • 74. Exercise: Print Personal Details • Write a program that will print your name and address to the console, for example: Alex Johnson 23 Main Street New York, NY 10001 USA
  • 76. Exercise: Sales Discount • Create a new project in Eclipse named Sale • Create, compile, and run the FriendsAndFamily class as illustrated below • Debug this program in your IDE to find out how it works
  • 77. Further Reading • Java Tutorials - https://docs.oracle.com/javase/tutorial/ • Java Language Basics - http://docs.oracle.com/javase/tutorial/java/nutsandbolts/index.html • Eclipse IDE Workbench User Guide - http://help.eclipse.org/kepler/index.jsp • Intelli J IDE User Guide - https://www.jetbrains.com/idea/documentation/ • Eclipse Tutorial - http://www.vogella.com/tutorials/Eclipse/article.html

Editor's Notes

  1. System is a final class from java.lang package. out is the reference of PrintStream class and a static member of System class. println is a method of PrintStream class.
  2. System is a built-in class... System is a final class from java.lang package. out is the reference of PrintStream class and a static member of System class. println is a method of PrintStream class.
  3. Variables hold the state of the program, and methods operate on that state. If the change is important to remember, a variable stores that change. That’s all classes really do. Java calls a word with special meaning a keyword It probably comes as no surprise that Java has precise rules about identifier names. Luckily, the same rules for identifiers apply to anything you are free to name, including variables, methods, classes, and fields. There are only three rules to remember for legal identifiers: The name must begin with a letter or the symbol $ or _. Subsequent characters may also be numbers. You cannot use the same name as a Java reserved word. As you might imagine, a reserved word is a keyword that Java has reserved so that you are not allowed to use it. Remember that Java is case sensitive, so you can use versions of the keywords that only differ in case. Please don’t, though.
  4. The Integer class wraps a value of the primitive type int in an object. An object of type Integer contains a single field whose type is int.In addition, this class provides several methods for converting an int to a String and a String to an int, as well as other constants and methods useful when dealing with an int.
  5. The last thing you need to know about numeric literals is a feature added in Java 7. You can have underscores in numbers to make them easier to read:
  6. Literals are valid values assigned to data types
  7. To sum up: - float is represented in 32 bits, with 1 sign bit, 8 bits of exponent, and 23 bits of the mantissa (or what follows from a scientific-notation number: 2.33728*1012; 33728 is the mantissa). - Double is represented in 64 bits, with 1 sign bit, 11 bits of exponent, and 52 bits of mantissa. By default, Java uses double to represent its floating-point numerals (so a literal 3.14 is typed double). It's also the data type that will give you a much larger number range, so I would strongly encourage its use over float. There may be certain libraries that actually force your usage of float, but in general - unless you can guarantee that your result will be small enough to fit in float's prescribed range, then it's best to opt with double.
  8. & (AND): Only TRUE if both operands are TRUE | (OR): Only FALSE if both operands are FALSE ^ (EXCLUSIVE OR): Only TRUE if both operands are DIFFERENT