Core Java Programming Language (JSE) : Chapter I - Getting Started

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Java Programming
Language SE – 6
Module 1: Getting Started
Module 1: Getting Started

Objectives
Upon completion of this module, you should be able to:
Describe the key features of Java technology●
Write, compile and run simple java application●
Describe the function of the Java virtual machine●
Define garbage collection●
List the three task perform by Java that handle code security●

Relevance
Is the Java programming language a complete language or is it●
useful only for writing programs for the Web?
Why do you need another programming language?●
This material also serves as a guide for Oracle Certified Java Professional
(OCJP), by making the flow in alignment with prescribed syllabus

What is Java Technology?
Java technology is:●
A programming language–
A development environment–
An application environment–
A deployment environment–
It is similar in syntax to C++.●
It is used for developing the applications.●
Thanks to its scalable nature, Java has emerged as the most preferred language
in Web and Mobile application development

Primary Goals of the
Java Technology
Provides an easy-to-use language by:●
Avoiding many pitfalls of other languages–
Being object-oriented–
Enabling users to create streamlined and clear code–
Provides an interpreted environment for:●
Improved speed of development–
Code portability–

Java Technology
Enables users to run more than one thread of activity●
● Loads classes dynamically; that is, at the time they are actually
needed
Supports changing programs dynamically during runtime by loading
classes from disparate sources
●
●
Furnishes better security

Java Technology
The following features fulfill these goals:
The Java Virtual Machine (JVMTM) 1●
Garbage collection●
The Java Runtime Environment (JRE)●
JVM tool interface●

The Java Virtual Machine
Provides hardware platform specifications●
Reads compiled byte codes that are platform-independent●
Is implemented as software or hardware●
Is implemented in a Java technology development tool or a Web●
browser
The Java Virtual Machine(JVM) make the code run in any platform, thereby
making it platform independent

Architecture of Java Virtual Machine

JVM provides definitions for the:
Instruction set (central processing unit [CPU])●
Register set●
Class file format●
Stack●
Garbage-collected heap●
Memory area●
Fatal error reporting●
High-precision timing support●

The majority of type checking is done when the code is compiled.●
Implementation of the JVM approved by Sun Microsystems must be
able to run any compliant class file.
●
The JVM executes on multiple operating environments.●

Garbage Collection
Allocated memory that is no longer needed should be deallocated.●
In other languages, deallocation is the programmer’s responsibility.●
The Java programming language provides a system-level thread to
track memory allocation.
●

Garbage Collection
Garbage collection has the following characteristics:
Checks for and frees memory no longer needed●
Is done automatically●
Can vary dramatically across JVM implementations●

JRE With a Just-In-Time
(JIT) Compiler

JVM Tasks
The JVM performs three main tasks:
Loads code●
●
●
Verifies code
Executes code

The Class Loader
Loads all classes necessary for the execution of a program●
Maintains classes of the local file system in separate namespaces●
Prevents spoofing●

The Bytecode Verifier
The code adheres to the JVM specification.●
The code does not violate system integrity.●
The code causes no operand stack overflows or underflows.●
The parameter types for all operational code are●
correct.
No illegal data conversions (the conversion of integers to pointers)●
have occurred.

Steps to install JDK for windows
Step 1: Download JDK for windows.

Step 2: Open and Run the file.

Core Java Programming Language (JSE) : Chapter I - Getting Started

Step 3: How to set Environment Variables?

A Simple Java Application
The Test.java Application
//
// Sample "Hello World" application
//
public class Test{
public static void main (String[] args) {
System.out.println(“Hello World”);
}
}

Compiling and Running
the TestGreeting Program
Compile Test.java:
Syntax: javac filename.java
●
javac Test.java
The Test.java is compiled.●
Run the application by using the following command:●
Syntax: java filename
java Test
Locate common compile and runtime errors.●

Java Technology Runtime
Environment

Core Java Programming Language (JSE) : Chapter I - Getting Started

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Core Java Programming Language (JSE) : Chapter I - Getting Started