01. Introduction to programming with java

Introduction to Java
The Java Platform,
The Java Language, JDK, Eclipse
Svetlin Nakov
Technical Trainer
www.nakov.com
Software University
http://softuni.bg

Table of Contents
1. Your First Java Program
2. The Java Language
3. The Java Platform and JVM
4. JDK – Java SE Development Kit
 Using javac and java
from the command line
5. Java IDEs
6. Java Documentation
2

3
 The "Java Basics" course is NOT for absolute beginners
 Take the "C# Basics" course at SoftUni first:
https://softuni.bg/courses/csharp-basics
 The course is for beginners, but with previous coding skills
 Requirements
 Coding skills – entry level
 Computer English – entry level
 Logical thinking
Warning: Not for Absolute Beginners

Your First Java Program
Writing and Running Java Code in Eclipse

A sample Java program:
public class HelloJava {
public static void main(String[] args) {
System.out.println("Hello Java!");
}
}
First Look at Java
5

}
}
Java Code – How It Works?
6
Define a class
"HelloJava"
Define the main(…) method
– the program entry point
Print a text on the console by calling the
method "println" of the class "System"

7
Formatting Java Code
}
}
The block after the { symbol
is indented right by a TAB.
The } symbol stays under
the block holding the {.
Class names in Java
are in PascalCase.
The { symbol stays
at the same line.
Method names in Java
are in camelCase.

File Names Should Match Class Names!
 In Java all public classes should stay in a file with the same name
 For example, the class HelloJava should be in the file
HelloJava.java
HelloJava.java
public static void main(String args[]) {
}
}

Your First Java Program
Live Demo

10
 Java is very popular programming language
 A syntax to describe computer programs
 Object-oriented, statically typed, similar to C#
 Easy to learn, easy to read, easy to understand
 Java is a development platform
 Java SE, Java EE, JavaFX, Java ME, Android
 Runs compiled Java code in a virtual machine (JVM)
 Runs on millions of devices, in any OS
What is "Java"?

12
 Java programming language
 High-level object-oriented general purpose language
 Statically typed (not dynamic like JavaScript)
 Type-safe (runs in a virtual machine, called JVM)
 Easy to learn, easy to read, easy to understand
 Good for large server-side projects
 Similar to C# and C++, but less capable
 Highly portable (write once, run everywhere)
The Java Programming Language

The Java Platform
Java, JVM, JDK

14
 Environment for execution of Java code
 JVM (Java Virtual Machine)
 Java programming language
 Powerful class library (Java API) and programing model
 Ability to run Java programs on any machine with JVM
 Windows, Linux, MacOS, Android, your TV, your car, ...
 Java Platform Editions
 Java SE, Java EE, Android, Java ME, Java Card, Java Embedded, …
The Java Platform

15
 Java 1.0a2 (1995) – started as platform for Java applets
 JDK 1.0 (1996) – Java language, JDK, JVM, standard API classes
 JDK 1.1 (1997) – AWT UI framework, JavaBeans, JDBC
 J2SE 1.2 (1998) – J2SE, J2EE, J2ME, Swing UI framework, collections
 J2SE 1.3 (2000) – HotSpot JVM, JavaSound, JNDI
 J2SE 1.4 (2002) – Java Web Start, JAXP, regular expressions
 J2SE 5.0 (2004) – generics, varargs, foreach, autoboxing, enums
 Java SE 6 (2006) – GUI improvements, JVM improvements, open-source
 Oracle buys Sun (2009) – Java becomes more open
 Java SE 7 (2011) – dynamic languages, new I/O, try-with-resources
 Java SE 8 (2014) – lambda expressions, streams API, JavaFX UI framework
The Java Platform – History

16
 JVM – Java Virtual Machine
 Executes compiled Java bytecode (compiled programs)
 Virtual environment for safe code execution
 Similar to CLR in .NET
 JRE – Java Runtime Environment
 A runtime environment for Java-based software
 Similar to .NET Framework
 JRE = JVM + Java API classes (standard Java libraries)
 Available for Windows, Linux, Mac OS X (no Android and iOS version)
Java Platform: Terminology

17
 JDK – Java Development Kit (Java SDK)
 The development platform for Java developers
 Consists of JRE (JVM + API classes) + compilers + tools
 Available for several OS: Windows, Linux, Mac OS X
 Note that Android SDK is not type of JDK (it is separate platform)
 Class file (.class file)
 A compiled Java code (or Python / Groovy / other language code)
 Holds Java bytecode + metadata
 Usually multiple class files are packed into a JAR archive
Java Platform: Terminology (2)

18
 JAR archive (.jar files)
 JAR archives hold a set of classes and resources
 Like the assemblies in .NET Framework (.dll files)
 JAR files are ZIP archives with files + manifest (metadata XML)
 Classpath
 A set of directories and JAR archives holding your application's
classes and resources (e.g. images, icons, sounds, etc.)
 When loading a class or resource, the JVM traverses the classpath
to find the requested classes or files
Java Platform: Terminology (2)

Java Compilation and Execution
public static void
main(String args[]) {
System.out.println(
"Hello Java!");
}
}
(source code)
Compilation (javac) CAFE BABE 6D61 696E 0100 1628 5B4C
6A61 7661 2F6C 616E 672F 5374 7269
6E67 3B29 5609 0011 0013 0700 1201
0010 6A61 7661 2F6C 616E 672F 5379
7374 656D 0C00 1400 1501 0003 6F75
7401 0015 4C6A 6176 612F 696F 2F50
7269 6E74 5374 7265 616D 3B08 0017
0100 0C48 656C 6C6F 2C20 4A61
(bytecode)Execution (java)
JVM
HelloJava.java HelloJava.class

20
Cross-Platform Java
 Cross-platform
compilation and execution
 Java / Python code 
.class / .jar files 
execution in the JVM
 JVM runs on many devices
 Bytecode is portable by
nature

Console-Based Compilation
and Execution of Java Code
Live Demo (in Linux and Windows)
21

22
 Java SE (Java Standard Edition)
 For standalone Java applications and Java applets
 Java EE (Java Enterprise Edition)
 For server-side, enterprise, Web applications and Web services
 A set of APIs and server specifications built on top of Java SE
 Java ME (Java Micro Edition)
 A pared down version of Java SE and API’s for embedded devices
 Android
 Android is Java-like platform for Android tablets and smartphones
Java Platform Editions

23
Java SE 8 Platform
* Learn more at http://docs.oracle.com/javase/8/docs/index.html

24
 In Java the classes usually stay in packages (like namespaces in C#)
 A package holds a set of classes and other (inner) packages
 Packages are included by "import package.subpackage.*"
 Project directory structure always follows the package structure
Packages in Java
src/org/softuni/main/Main.java
package org.softuni.main;
import org.softuni.data;
public class Main { … }
src/org/softuni/data/Student.java
package org.softuni.data;
public class Student { … }

25
 A JAR file holds a set of classes
and resources
 Folders follow the package
structure of the classes
 JAR files are ZIP archives
 Created by Eclipse or by a
console tool called "jar"
Creating a JAR File
jar -cf archive.jar <files>

Creating a JAR File and
Configuring the Classpath
Live Demo

27
 A programming language
 Java, C#, PHP, Python, …
 Task to solve: project description
 Development platform: IDE, compilers, SDK
 IDE (Eclipse, NetBeans, Visual Studio), Java SDK, Android SDK
 Set of standard classes (class library)
 Java API classes / .NET API classes / PHP standard functions
 Help documentation
 Java API documentation / .NET API documentation
What You Need to Program?

Java IDEs
Eclipse, NetBeans, IntelliJ IDEA

29
 Eclipse is popular IDE (Integrated Development Environment)
 For many languages: Java, PHP, Python, JavaScript, HTML, CSS, …
 Eclipse is IDE that helps us to:
 Write code
 Design user interface
 Compile code
 Execute / test / debug code
 Browse the help
 Manage project's files
Eclipse – IDE for Java Developers

30
 Eclipse is a single tool for:
 Writing code in many languages (Java, PHP, C++, JavaScript…)
 Using different technologies (Web, mobile, embedded, …)
 Complete integration of most development activities
 Coding, compiling, running, testing, debugging, UI design,
deployment, version control, ...
 Free and open-source – www.eclipse.org
 Easy to use and intuitive
Benefits of Eclipse

Eclipse IDE
Creating, Compiling, Running and
Debugging Java Programs – Live Demo

 NetBeans is an open-source IDE for Java developers
 Supports Java, C++, PHP, HTML5
 Developed by Oracle (formerly by Sun Microsystems)
 Written in Java, runs on Windows, Linux, Mac OS X
 Supports the latest Java SE and Java EE technologies
 Integrated features: code editor, debugger,
profiler, GUI editor, source control tools, etc.
 www.netbeans.org
NetBeans

 IntelliJ IDEA is а powerful IDE for Java developers
 Very good usability, helps you a lot with writing code
 Supports Java, PHP, Python, Ruby, HTML5, SQL
 The free edition support only Java and basic features
 Advanced features, PHP, Python, Ruby, SQL, Java EE,
Android, etc. are commercial
 Written in Java, runs on Windows, Linux, Mac OS X
 http://www.jetbrains.com/idea/
IntelliJ IDEA

37
 Java 8 API Documentation
 http://docs.oracle.com/javase/8/docs/api/
 Complete documentation of all classes and their functionality
 With descriptions of all methods, properties, events, etc.
 Java 8 official documentation:
 http://docs.oracle.com/javase/8/docs/
 The Java Tutorial
 http://docs.oracle.com/javase/tutorial/
Java Documentation

Java API Documentation
Live Demo

39
 The Java platform consists of
 The Java language
 Java Virtual Machine
 Java API classes
 One Java platform, several editions
 Java SE, Java EE, Java ME, Android
 JDK = JRE + compilers and tools
 Eclipse – powerful open-source Java IDE
Summary

?
https://softuni.bg/courses/java-basics/
Introduction to Java

License
 This course (slides, examples, demos, videos, homework, etc.)
is licensed under the "Creative Commons Attribution-
NonCommercial-ShareAlike 4.0 International" license
 Attribution: this work may contain portions from
 "Fundamentals of Computer Programming with Java" book by Svetlin Nakov & Co. under CC-BY-SA license
 "C# Basics" course by Software University under CC-BY-NC-SA license
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Free Trainings @ Software University
 Software University Foundation – softuni.org
 Software University – High-Quality Education,
Profession and Job for Software Developers
 softuni.bg
 Software University @ Facebook
 facebook.com/SoftwareUniversity
 Software University @ YouTube
 youtube.com/SoftwareUniversity
 Software University Forums – forum.softuni.bg

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