Programming in JAVA 👨‍💻

Binary Number System

We humans use a decimal, or base-10, numbering system, presumably because people have 10 fingers

Early computers were designed around the decimal numbering system. This approach made the creation of computer logic capabilities unnecessarily complex and did not make efficient use of resources. (For example, 10 vacuum tubes were needed to represent one decimal digit.)

Story behind

To deal with the basic electronic states of on and off, Von Neumann suggested using the binary numbering system

Conversions

Binary Number to Decimal
Decimal Number to Binary

Programming in JAVA

What happens behind the scenes?

Why Java is Platform independent.

.java file

(source code)

.class file

(byte code)

Machine Code (0s & 1s)

compiler

interpreter

What happens behind the scenes?

Why Java is Platform independent.

.java file

(source code)

.class file

(byte code)

Machine Code (0s & 1s)

compiler

interpreter

Byte Code doesn't run directly, we need a JVM (Java Virtual Machine) to run this code

Platform Independence?

Byte-Code can run all operating systems

C++

C/C++ Compiler generates a .exe file which is platform dependent.

Java

In Java we get bytecode, JVM converts this bytecode into machine code.

To run byte-code, we need a JVM installed on a machine.

Java is platform independent but JVM is platform dependent.

Python

Python is interpreted language, instructions are executed line by line.

Software Tools [Recommended] 🤔

IntelliJ Idea (IDE)

https://www.jetbrains.com/idea/download

(Free Community Edition)

JDK

https://www.oracle.com/java/technologies/downloads/#java16

Architecture

JDK = JRE + Development Tools

JRE = JVM + Library Classes

JDK = JRE + Development Tools

Java Virtual Machine (JVM)

JIT Compiler

(Just In Time)

JDK

Consists of Development tools & environment to run the Java program.

1. Development Tools

2. Compiler (javac)

3. Archiver (jar)

4. docs generator (javadoc)

5. interpreter / loader

JRE

Provides environment to only run the program.

JRE = JVM + Additional technologies & features

1. Deployment solutions

2. Development toolkits & libraries

3. Integration libraries

4. Language and utility libraries

(such as collections framework)

JVM 🤔

Java Virtual Machine

JVM

Java Virtual Machine, or JVM, loads, verifies and executes Java bytecode. It is known as the interpreter or the core of Java programming language because it executes Java code.

Class Loader Subsystem is responsible for loading, linking and initializing a Java class file (i.e., “Java file”), otherwise known as dynamic class loading.
Runtime Data Areas contain method areas, PC registers, stack areas and threads.
Execution Engine contains an interpreter, compiler and garbage collection area.

Summary

The JRE combines Java code created using the JDK with the necessary libraries required to run it on a JVM and then creates an instance of the JVM that executes the resulting program.

JVMs are available for multiple operating systems, and programs created with the JRE will run on all of them. In this way, the Java Runtime Environment is what enables a Java program to run in any operating system without modification.

Coding Minutes IDE

ide.codingminutes.com

No Installation Required!
Directly Run | Save | Share Codes!

Recommended for beginners

First Java Program

Boilerplate Code

//Boilerplate Code
class Main
{
	public static void main (String[] args)
	{	

	}
}

First Java Program

Boilerplate Code

//Boilerplate Code
class Main
{
	public static void main (String[] args)
	{	
    		//Your Code goes here
	}
}

First Java Program

Boilerplate Code

//Boilerplate Code
class Main
{
	public static void main (String[] args)
	{	
    		//Your Code goes here
    		System.out.println("Hello World");
	}
}

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Let's Solve Problems & learn Java syntax!

1. Hello Java

2. Variables

3. Loops

4. Typecasting

5. Problems - Prime Numbers, Patterns, Simple Interest

variable = (condition) ? expressionTrue :  expressionFalse;

Ternary Operator