Java Tutorial
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Welcome to the exciting world of Java! An enthusiast might not need an introduction to Java. It is more than just a programming language. Java is a platform for creating a diverse range of applications. From mobile apps to web services and games, Java offers tools to bring your digital vision to life.
First, let's demystify what Java is. Think of it as a set of instructions that tell computers what to do. It's like a recipe for your system, guiding it to execute tasks accurately and efficiently. Known for its 'Write Once, Run Anywhere' feature, Java code can work on various platforms without the need for recompilation. Continue reading this Java tutorial to learn more.
We'll be time-traveling to the '90s when a team from Sun Microsystems sparked a programming revolution. Meet the 'Green Team' - the dreamers and creators of Java.
They initially set out to craft a language for gadgets like televisions and phones. But destiny had grander plans! They gave birth to a programming language in 1995, making an introduction to Java, which shook the foundations of the programming universe.
Here's the real magic of Java: its 'Write Once, Run Anywhere' feature. It means a developer can whip up code just once, and it will run on any device.
But Java didn't rest on its laurels. It kept changing, morphing to fit the digital world's ever-evolving demands. Java went from breathing life into business servers to steering Android app development, making its mark everywhere.
Today, it stands tall as one of the most popular programming languages globally.
Programming languages are a lot like tools in a toolbox; each one has its own unique strength, and choosing the right one depends on your project. Today, we'll examine the characteristics of three popular languages: Java, C++, and Python.
Feature | Java | C++ | Python |
Syntax Simplicity | Moderately complex syntax | More complex syntax | Simple, English-like syntax |
Speed | Generally slower than C++, but faster than Python | Outperforms Java and Python | Relatively slower |
Memory Management | Automatic (Garbage collection) | Manual | Automatic |
Portability | Excellent (JVM) | Requires more care due to system-level access | Good, but dependent on Python interpreters |
Use | Enterprise-scale applications, Android development, web applications | Game development, real-time systems, high-performance applications | Data analysis, machine learning, web development, scripting |
Visit the Official Java Download Page
Start by going to the official Oracle's Java download page at www.oracle.com/java/technologies/javase-jdk11-downloads.html
Choose the Appropriate JDK
Depending on your operating system, choose the right Java Development Kit (JDK) download link. (In this example, we will proceed with the Windows OS)
Download the Installer
Click on the download link next to your operating system. Accept the license agreement if required, and then the download should start.
Run the Installer
As soon as your download is complete, you'll need to find the installer file. Double-click the installer to run it.
Follow the Installation Prompts
An installation wizard will guide you through the process. Just follow the instructions, which usually involve accepting the terms and conditions.
Choose Install Location (Optional)
You will typically have the option to choose where you want the JDK installed. If you're unsure, just go with the default location that the installer suggests.
Finish the Installation
The installer will then copy the necessary files to your system.
Verify the Installation
Open a command prompt and type java -version. If Java is installed correctly, it will display the version.
Find the Java Installation Directory
If you installed Java with the default settings, the Java Development Kit (JDK) should be in a specific location on your computer based on your operating system. On Windows, it is typically under C:\Program Files\Java\jdk<version>.
Set JAVA_HOME
You need to set the JAVA_HOME environment variable to point to your JDK installation directory.
Windows:
Open the Control Panel and search for 'Environment Variables.'
Click on 'Edit the system environment variables'.
In the 'System Properties' window, go to the 'Advanced' tab and click 'Environment Variables'.
Click 'New' under 'System variables', and enter 'JAVA_HOME' as the variable name and the JDK installation directory path as the variable value.
Add Java to the PATH
This step allows you to run the Java command from any directory without having to type the full path of the command.
Windows:
Follow steps 1-3 as described in 'Set JAVA_HOME.'
Look for the 'Path' variable under 'System variables,' and click 'Edit.'
In the 'Edit Environment Variable' window, click 'New' and add %JAVA_HOME%\bin
4. Verify the Setup
Close and reopen your command prompt.
Run the command java -version. If the setup is successful, it will display the installed Java version.
Run the command echo $JAVA_HOME. It should display the path to your JDK installation directory.
Visit the Eclipse Official Website
Start with the official Eclipse download page at www.eclipse.org/downloads
Choose the Eclipse Package
Click on the "Download Packages" link if you prefer a specific version like "Eclipse IDE for Java Developers" or "Eclipse IDE for Enterprise Java Developers". If you're not sure, you can download the "Eclipse Installer," which will provide you with options later.
Select Your Operating System
Ensure you're downloading the right version for your operating system.
Download the Installer
Click on the download link, and it should start automatically.
Run the Installer
Locate the installer file and double-click to run it.
Choose the Eclipse Version
If you downloaded the "Eclipse Installer," you will see a selection of different packages to install, such as "Eclipse IDE for Java Developers" or "Eclipse IDE for Enterprise Java Developers." Choose the one that you need.
Installation Folder:
Choose the location where you want Eclipse to be installed.
Complete the Installation:
The installer will then copy the necessary files to your system. When it's finished, it will tell you that Eclipse has been successfully installed.
Run Eclipse
You can now run Eclipse from the start menu or the shortcut created on your desktop.
Verify the Installation
You can verify the installation by launching Eclipse and creating a new project to make sure everything works as expected.
Remember, Eclipse requires a compatible version of Java JDK installed on your computer.
The Java Development Kit (JDK) is a software development environment. It is used for developing Java applications and applets. It is an official development package released by Oracle Corporation and includes the Java Runtime Environment (JRE), an interpreter/loader (Java), a compiler (javac), an archiver (jar), a documentation generator (javadoc), among other tools needed in Java development.
Getting started with the Eclipse IDE involves many steps, from creating a new project to writing and running your first Java program. Here's a step-by-step guide:
Launch Eclipse IDE
Start Eclipse. Upon launch, it will ask you to select a workspace, which is a folder where your projects and their files will be stored. Choose a directory that's easy for you to access.
Create a New Java Project
Go to the 'File' menu, choose 'New', and then select 'Java Project'. A window will open where you can name your project. Fill in your desired project name, tick the "Use default location" checkbox, and click 'Finish.'
Create a New Java Class
In the 'Package Explorer' on the left side of the IDE, you should now see your new project. Right-click on 'src' under your project, go to 'New', and select 'Class.' Provide a name for your class as per Java naming conventions and check the 'public static void main(String[] args)' option. This tells Eclipse to create a main method in your class, which is the entry point for any Java application. Click 'Finish.'
In Java, Strings are objects that represent sequences of characters. The ‘java.lang.String’ class creates and manipulates strings.
There are two ways to create Strings in Java:
String Literal: Java String literal is created by using double quotes.
Here, 'Hello' is a string literal. The String object s is being assigned to hold 'Hello.' In this case, Java will use an existing "Hello" string from the "String Constant Pool" or create a new one there if it doesn't exist.
New Keyword: Java String is created by using the keyword new.
Here, a new String object s is created in the heap memory with the value 'Hello'.
The String class comes with numerous methods for manipulating strings. Here are a few examples:
length(): Returns the length of the string.
charAt(int index): Returns the character at the specified index.
concat(String str): Concatenates the specified string to the end of this string.
indexOf(int ch): Returns the index within this string of the first occurrence of the specified character.
substring(int beginIndex): Returns a new string that is a substring of this string.
equals(Object anObject): Compares this string to the specified object.
Here's a simple example of using some of these methods:
This code will output:
Strings in Java are immutable, meaning they cannot be changed once created. A new String object is created every time you perform an operation on a string.
JVM (Java Virtual Machine) | JIT (Just-In-Time Compiler) | |
Definition | JVM is a virtual machine that provides a runtime environment to execute Java bytecode. It's part of the Java Runtime Environment (JRE). | JIT is a part of JVM that improves the performance of Java applications by compiling bytecodes into machine language at runtime. |
Function | Main function is to interpret the compiled Java binary code (.class file) line by line and execute the program. | JIT compiles parts of the bytecode that have similar functionality and reduces the amount of time needed for compilation. |
Platform | It is platform-dependent, which means a separate JVM is needed for each operating system. | JIT is a part of JVM and is thus is also platform-dependent. |
Performance | Due to its interpretive nature, the JVM is generally slower in execution. | JIT significantly improves the performance of Java applications by reducing the amount of time needed for compilation. |
Compilation | JVM interprets bytecode into machine code at runtime. | JIT compiles bytecode into machine code at runtime but does so more efficiently by compiling similar parts of bytecode at the same time. |
Memory | JVM uses more memory | It generally uses less memory than JVM. |
Java achieves platform independence through its use of bytecode and the Java Virtual Machine (JVM):
Compilation to Bytecode
Java source code is compiled to platform-independent bytecode rather than platform-specific machine code.
Execution by JVM
The JVM, which is platform-dependent, interprets the bytecode and translates it to machine code that's specific to the underlying hardware and operating system. This allows the same Java program to run on any device equipped with a JVM, making Java "write once, run anywhere."
Why is the "Introduction to Java" essential for aspiring developers?
"Introduction to Java" is crucial for aspiring developers as it lays the foundation for understanding Java, one of the most widely-used programming languages. It equips them with key concepts like object-oriented programming and Java's syntax, aiding in developing robust applications. Furthermore, it provides the groundwork for grasping more complex Java frameworks and technologies.
What are the career opportunities after learning Java programming?
The career opportunities for Java experts include Java Web Developer, Java Android Developer, Software Developer, Solutions Architect, Systems Analyst, etc.
I'm new to coding. Why is everyone telling me to start with Java?
Java is often the top pick for newbies because it's an object-oriented language. It helps you grasp key concepts used in many other languages. Its syntax has a lot in common with other popular languages, so once you've mastered Java, you'll find other languages a breeze.
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