A Comprehensive Guide to Classes, Variables, Keywords , Methods, Modifiers and the Main Method in Java

 

A Comprehensive Guide to Classes, Variables, Keywords , Methods, Modifiers and the Main Method in Java

 Class

A blueprint used to create an object is called a class. Various objects can be created related to one class. The limit of the class is only the class, the constructor of the class, and the main method.  The methods of the class do not belong to the limits of the class.


If you want to know more about class read this blog post.

Variable

 In Java, a variable is a storage location used to store information that can be changed during program execution.  That is, a variable is a named storage location where data is stored and can be referenced and manipulated in a program.  There are two types of variables in Java.  Variables are governed by the type of data they can hold.



Static

A static variable in Java is a class variable declared using the static keyword.  It is associated with the class itself, and only one copy of the static variable is shared among all instances of the class.  It can also be called a variable that belongs to the class rather than any specific instance of the class. This variable is accessed anywhere in the class.

Keypoints👇

👉Changes made to a static variable in one instance are represented in all instances and all instances of the class share the same static variable. 

👉The class name is used to access static variables.

👉 Static variables can be modified directly using the class name or through an instance of the class, but sometimes doing so creates confusion, so static variables are accessed and modified using the class name.

👉Static variables are used to represent properties that are shared across all instances of a class.  

Local variable

In Java, a local variable is a variable inside a method, that is, a variable declared inside a constructor or code block.  Local variables must be explicitly declared and initialized before they are used.  Local variables can only be accessed within the scope in which they are defined.  And they remain for the duration of that scope and once the scope goes out, the local variable goes out of scope and reclaims its memory.

Key points 👇

👉 Local variables are accessible only within the code block in which they are declared.  They have a limited scope. Attempting to access them outside that scope will result in a compilation error.

👉Local variables must be explicitly initialized before they can be used.  Attempting to use an uninitialized local variable will result in a compilation error.

👉The lifetime of a local variable is limited to the block duration of the code in which it is declared.  Once the code exits the block, the local variable is no longer accessible, and its memory is reclaimed.

👉Each invocation of a method or code block gets its own local variables.  This makes local variables thread safe in the context of method execution.

Instance variable

An instance variable is a variable that belongs to a specific instance of a class. Instance variables are used to store data that is unique to each instance of the class. It is a variable in the limit of the class.

Keywords

Keywords are an integral part of the Java programming language and are reserved words that have special meanings and cannot be used as identifiers . They are used to define various elements and functions. Some keywords, like Const, Goto  are currently don't have any functionality in the language.


Method

A group  of codes that perform a specific task or operation is called this.  Methods are defined within classes and are used to organize and structure code.  They encapsulate functionality, making code modular and reusable.




Modifiers

Modifiers are keywords that provide additional information about classes, variables, and methods. They are used to control access, visibility, and behavior of these elements. There are two main categories of modifiers in Java,



Non Access Modifier

Static

The element belongs to the class rather than to instances of the class. For methods, it means the method can be called without creating an instance of the class.

Access Modifier


Private 

 The element is accessible only within its own class.

default (no modifier)

The element is accessible only within its own package.

Protected

The element is accessible within its own package and by subclasses.

Public

 The element is accessible from any other class.

Main Method

The main method is the entry point of a Java program.

public

The main method must be public so that it can be accessed by the JVM.

static

The main method must be declared as static because it is called by the JVM before any objects are created.

void

The main method does not return any value.

main

This is the name of the method. The JVM looks for a method with exactly this signature when starting the program.

String[] args

The main method takes an array of strings as its parameter. This parameter allows you to pass command-line arguments to your Java program.

 The args parameter is an array of strings where each element contains a command-line argument.


Article by-: Rasanjali Herath

E-Mail-: rasanjaliherath899@gmail.com



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