Java is a popular and widely used programming language for several reasons. Here are some of the key factors that make Java a compelling choice for many developers and organizations
1. Platform Independence: Java is known for its "write once, run anywhere" capability. It accomplishes this through the use of the Java Virtual Machine (JVM), which allows Java applications to run on any platform that has a compatible JVM. This means you can develop an application on one platform and run it on various other platforms like macOS, ubuntu, Linux without modification.
2. Strongly Typed Language: Java is a statically typed language, which means that it requires variable types to be declared before use. This can help catch many errors at compile time, making it easier to write reliable code.
3. Object-Oriented: Java is an object-oriented programming language, which promotes the use of classes and objects. This approach makes it easier to model real-world problems and develop maintainable and modular code.
4. Rich Standard Library: Java provides a comprehensive standard library with a wide range of classes and methods for common programming tasks. This library covers everything from data structures to network communication, making it easier to develop applications without reinventing the wheel.
5. Security: Java has built-in security features to protect against various security threats, such as unauthorized access and malicious code execution. The JVM includes a security manager and bytecode verification to ensure a secure execution environment.
6. Memory Management: Java uses automatic memory management through a process called garbage collection. This relieves developers from the need to manage memory manually, reducing the risk of memory-related bugs like buffer overflows and memory leaks.
7. Community and Ecosystem: Java has a large and active developer community, which means you can find a wealth of resources, libraries, and frameworks for almost any type of project. It's used in various domains, from web development (Java EE, Spring) to Android app development (Java for Android).
8. Scalability: Java is known for its ability to build large-scale, high-performance applications. It's commonly used in enterprise software, web applications, and other systems that require scalability and reliability.
9. Backward Compatibility: Java places a strong emphasis on maintaining backward compatibility. This means that code written in older versions of Java can often run on newer Java runtimes without modification.
10. Robustness and Reliability: Java has features that contribute to the robustness and reliability of applications, such as exception handling and strong typing, which help prevent crashes and errors.
11. Multithreading and Concurrency: Java provides built-in support for multithreading and concurrency, making it well-suited for developing applications that can efficiently utilize modern multi-core processors.
While Java has many advantages, it may not be the best choice for every project. The choice of programming language depends on the specific requirements of your project and your team's expertise. There are many other programming languages available, each with its own strengths and weaknesses.
JVM ARCHITECTURE
The Java Virtual Machine (JVM) is a crucial component of the Java platform, responsible for executing Java applications. It's designed to be platform-independent, allowing Java code to run on various operating systems. The JVM architecture consists of several components:
1. Class Loader:
- Responsible for loading classes into memory.
- Classes are typically loaded from class files or other sources like networklocations.
- Class loading is essential for the dynamic nature of Java applications.
2. Class Memory Area:
- Divided into several components, including Method Area, Heap, and others.
- Method Area stores class-level structures such as class definitions, methods, and static fields.
- Heap is where objects are allocated and deallocated during runtime.
3. Execution Engine:
- Executes bytecode instructions.
- Consists of the Just-In-Time (JIT) compiler, which compiles bytecode into
native machine code for better performance.
- The JVM interpreter can also directly execute bytecode.
4. Java Native Interface (JNI):
- Enables interaction between Java code and native code (written in languages like C and C++).
- Useful for integrating platform-specific functionality and libraries.
5. Native Method Interface (NMI):
- Similar to JNI but used for calling native methods from Java classes.
6. Java Native Interface (JNI):
- Enables interaction between Java code and native code (written in languages like C and C++).
- Useful for integrating platform-specific functionality and libraries.
7. Native Method Interface (NMI):
- Similar to JNI but used for calling native methods from Java classes.
8. Native Method Libraries:
- Contains the native methods provided by the JVM and the operating system.
- These methods are used for low-level tasks, such as memory management and system calls.
9. Stack:
- Stores the call stack, which holds method call frames.
- Each frame contains local variables, operand stack, and the program counter.
- Used for method invocation and maintaining control flow.
10. Program Counter (PC) Register:
- Keeps track of the current execution point within a method.
- Helps in the sequential execution of bytecode instructions.
11. Execution Control:
- Responsible for managing thread synchronization, garbage collection, and exception handling.
- Ensures the proper execution of Java code and manages resources efficiently.
12. Security Manager:
- Enforces security policies to protect the system from potentially harmful code.
- Defines what operations Java code is allowed to perform, such as file access and network communication.
13. Thread Management:
- Manages multiple threads in a Java application.
- Ensures thread safety and coordination among threads.
Types of Applications Where Java Used
There are various types of applications in software development, each designed to serve different purposes and address specific needs. Here are some common types of applications:
Desktop Applications:
These are applications designed to run on a user's local computer or device.
They provide platform-specific user interfaces and often have better performance.
Examples include word processors, graphic design software, and video games.
Web Applications:These applications run on remote web servers and are accessed through web browsers.
Users can access them from anywhere with an internet connection.
Examples include email services, social media platforms, and online shopping websites.
Mobile Applications:
Designed for smartphones and tablets, these apps run on mobile operating systems like Android and iOS.
They can be downloaded and installed from app stores.
Examples include mobile games, social networking apps, and navigation apps.
Embedded Applications:
Software that is integrated into hardware devices and systems.
Examples include firmware in smartphones, car navigation systems
and IoT.
History of Java
1991: Java is created by James Gosling, Mike Sheridan, and Patrick Naughton at Sun Microsystems. It was originally known as "Oak."
1995: The official release of Java 1.0 by Sun Microsystems. This marked the beginning of the "Write Once, Run Anywhere" (WORA) concept.
1996: Java Applets became popular for web development. The "applet" allowed Java programs to run within web browsers.
1997: Java 1.1 introduced significant improvements and the event model, which made it easier to build GUI applications.
2000: Java 2 (J2SE) was released, bringing a new platform, improved performance, and the Swing GUI toolkit.
2004: Java 5 (also known as J2SE 5.0 or Java 1.5) was a major release with features like Generics, Metadata Annotations, and enhanced "for-each" loop.
2006: Sun Microsystems open-sourced Java under the GNU General Public License (GPL), known as OpenJDK.
2011: Java 7 was released with features like the try-with-resources statement and the diamond operator for simplified generics.
2014: Java 8 introduced lambdas, the Stream API for functional programming, and the java.time package for modern date and time handling.
2017: Java 9 brought modularization with the introduction of the module system and the "jshell" for a Read-Eval-Print Loop (REPL).
2018: Java had a new release cadence, with Oracle releasing Java every six months. Java 10, Java 11, and later versions followed, offering incremental improvements.
2020: The release of Java 15 featured sealed classes and records, adding more language features and enhancements.
2021: Java 16 introduced pattern matching and improvements to garbage collection and performance.
2022: Java 17 was a Long-Term Support (LTS) release, offering stability and ongoing support.
What is class?
class is the blueprint of an object having some states and behaviors
What is an object?
object is anything present in the real world and having some physical existence.
example:-car, bike, atm, mobile, etc
What is a variable?
variables are containers used to store some particular data into it.
example:- godowns used to store different types of products.
What is data type? and its types
In a variable what kind of data we are storing is called as datatype.
There are mainly two kinds of data types in Java we have
1. Primitive data type
2. Non primitive data type
1. Primitive data type
a.byte, short,int, long
b.double, float
c.boolean
d. char,String
2.Non primitive data type
class, objects are kind of non-primitive data types in java
Byte- size is 8 bit=1-byte
char- 2 bytes
short-2 bytes
int -4 bytes
long-8 bytes
double-8 bytes
float-4 bytes
boolean-1 bit
Function:-
function is a block of code used to perform some specific task.
example:- here getString() is used to return some string value to perform task .
public String getString(String str){
return str;
}
Method overloading:-
When class is having one or more same methods but differences in the of arguments or arguments order or datatypes of arguments. Then this type of methods are called as overloaded methods.
example:-
class Moblie{
void createContact(int number1){
System.out.println("number1");
}
void createContact(int number1, int number2){
System.out.println("number1 and number2");
}
public static void main(String[] args){
Moblile mobile=new Mobile();
mobile.createContact(9012341011);
mobile.createContact(9012341011,9536664783);
}
}
Method overriding:-
When a both super class and sub class having same methods then subclass method will override the superclass method and gives sub class method .This process in java is called as method overriding.
Rules for Java Method OverridingThe method must have the same name as in the parent class
The method must have the same parameter as in the parent class.
There must be an IS-A relationship (inheritance).
void makeSound()
{ System.out.println("The animal makes a generic sound");
}
}
class Dog extends Animal {
@Override
void makeSound()
{
System.out.println("The dog barks");
}
}
public class Main {
public static void main(String[] args) {
Dog dog = new Dog();
dog.makeSound();
}
}
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