Java Basics - Tutorial

Wikipedia claims that there

are almost 10 million  Java developers all the world with this we can understand the popularity of Java.This Java tutorial is for beginners who wanted to know the basic  of  Java.
Java technology  is  object oriented programming language as well it provides the JRE  platform.

Features of  Java

• Simple- Java is very simple represented language because of OOPs principle.

• Object Oriented- Java supports Object Oriented Programming that helps in maintainability, extensibility, and reusability.

• Robust-Java comes with of compile time error elimination.

• Portable - Java is platform independent so we take it to any machine.Once byte code is generated we can run byte code on any platform.

• Multithreaded- Java supports multithreading i.e. we can perform multiple tasks simultaneously thus help in the better use of CPU resources.

• Secure
• Automatic Garbage Collection- Object without reference gets garbage collected .

JVM,JDK , and  JRE

• JDK(Java Development Kit)- JDK consists of JRE and other development tools such as java,javac(compiler),Javadoc etc.

• JRE(Java Runtime Environment)-It provides Java runtime libraries along with JVM.

• JVM(Java Virtual Machine)-It machine on which byte code(.class file) executes.JVM converts byte code to machine code.JVM provides  memory management,garbage collection.

Fig 1.1

JDK, JRE and JVM are platform dependent.

Java code execution flow.

• Java soure code(.java) get compiled using Java compiler(javac) into byte code(.class).
• JVM loads byte code and other libraries.
• Execution of the byte code takes place in JVM (Shown in Fig 1.3).

Fig 1.2

JVM Component

JVM internal processing steps are represented in below flow diagram

Fig 1.3

Get into details of JVM Memory Allocation

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