DEV Community: Chithra Priya

Collections in Javascript

Chithra Priya — Wed, 27 Aug 2025 06:32:23 +0000

Java OOPS Concept..

Chithra Priya — Tue, 05 Aug 2025 09:44:18 +0000

1.Class:

What - Class is a blueprint or template for creating a objects. It defines variables and methods.
Why - To organize code, reuse functionality, and implement OOPS concepts.
How - Define a class using the class keyword. Add variables and methods. Create objects of the class using the new keyword.
Syntax:

class class_name
{
field;
method;
}

2.Variable:

Variable is a container, used to store the value (or) data.
What is Local Variable - Local variables declared inside the method. It only accessable within that method.
What is Global variable - Global variables are declared outside the method. It can be access outside the method.

Class in java

Chithra Priya — Tue, 05 Aug 2025 09:37:08 +0000

Class:

A class is a group of objects which have common properties. It is a blueprint or template from which object is created. It is logical entity. Class is a user defined blueprint or prototype from which objects are created.
In java class contains:

Fields
Methods
Constructor
Blocks
Nested class
Interface

Syntax to declare a class:

class class_name
{
field;
method;
}

Constructor, this keyword, Packages...

Chithra Priya — Tue, 22 Jul 2025 00:18:54 +0000

Difference between zero argument constructor and default constructor in Java?

Default Constructor:**

A constructor that is automatically provided by the Java compiler when no constructor is defined in the class.
It has no parameters (zero-arguments) and no body code.
It initializes instance variables to default values (e.g., 0 for int, null for objects).

Example:

public class MyClass {

}

Zero-Argument Constructor:

A constructor that is explicitly written by the programmer with no parameters.
It has no parameters, it is not considered a default constructor, because it's written by developer. Example:

public class MyClass {
    MyClass() {
        System.out.println("zero-argument constructor");
    }
}

This:

This is a keyword.
This refers to current object.It is used to define global variable.
This keyword is used to differentiate between local and global variable.
When local variable names are the same as instance variables, this is used to differentiate.

Example:

public class Student {
    String name;

    public Student(String name) {
        this.name = name; 
    }
}

Package:

In java package means folder.

Why Use Packages in Java?

Grouping similar file.
Avoid naming conflict.

Create package:
package com.indianBank;

Compile package:
javac -d . classname.java

Run package:
java filename

Constructor in Java:

Chithra Priya — Thu, 17 Jul 2025 07:38:35 +0000

Constructor:

Constructor is method used to initialize object specific values to variables. JVM have default constructor.

Why use constructor?

Each object gets initialized properly when it’s created.
Helps reduce code repetition.

Characteristics:

Constructor name as same as class name.
No return type required.
Automatically called when object is created.
Initialize object specific values to variable.

Types of Constructor:
1. Default Constructor:

A constructor with no parameters.
If you don’t write any constructor, Java provides one by default.

Program for Default Constructor:

class Car {
    Car() {
        System.out.println("Car is created");
    }
}

public class Main {
    public static void main(String[] args) {
        Car myCar = new Car(); 
    }
}

Output:
Car is created

2. Argument Constructor:

Constructor that takes arguments to initialize the object with specific values.

Program for Argument Constructor:

public class Market
{
static String marketName = "Nehru";
String prodname;
int price;

public Market(String s, int i)
{
System.out.println("I'm constructor");
prodname = s;
price = i; 
}

public static void main(String[] args)
{
Market prod1 = new Market("abc",100);
Market prod2 = new Market("xyz",1000);
System.out.println(prod1.prodname);
System.out.println(prod2.prodname);
System.out.println(prod2.price);
}
}

Output:
I'm constructor I'm constructor abc xyz 1000

Method Overloading in Java...

Chithra Priya — Wed, 16 Jul 2025 12:00:10 +0000

Polymorphism is one of the oops pillars in java. It has two types. They are,
1.Compile time polymorphism (or) Method Overloading 2.Run time polymorphism (or) Method Overriding

1.Method Overloading:

Method Overloading allows multiple methods with the same name but different number and types of arguments within a class.
Method Overloading is very important to naming convertion.

Example:

public class SuperMarket
{
static String shopname = "Kanchi Super Market";
String product_name;
int price;

public static void main(String[] args)
{
SuperMarket product = new SuperMarket();
product.buy(10);
product.buy(5,50);
product.buy(10.5f, 10.3f);
product.buy(100.5d);
}

void buy(int no)
{
System.out.println("buy one args" +"=" +no);
}

void buy(int no1, int no2)
{
System.out.println("buy two args" +"=" +no1+" "+no2);
}

void buy(float no3, float no5)
{
System.out.println("buy two float args" +"=" +no3+" "+no5);
}

void buy(double no4)
{
System.out.println("buy one double args"+"=" +no4);
}

}

Output:

buy one args=10
buy two args=5 50
buy two float args=10.5 10.3
buy one double args=100.5

Keywords, Methods, Objects, Void, Return type & Variables...

Chithra Priya — Tue, 15 Jul 2025 10:48:10 +0000

=====>> [TBD]
_Method have two types. They are,

Method Overloading
Method Overriding_

Keywords:

Static:
Static refers to class specific information.
Class have common for all objects.
only one memory copy.

Non-static:
Non-static refers to object specific information.
object have specific information.
Multiple memory copy.

Method:

Method is a set of instruction with a name to perform specific task.
Method has return type.

Example:

String buy()
{
System.out.println("buy method");
}

Object:

Object is a combination of state and behaviour.

Syntax for creating a object:

Home person = new Home();

new - is a keyword creating a new space to new object.
Home - is a class name
person - represents object name

Void:

Void is a return type of the method.
Not return anything and doing something inside the method.

Return type:

Return is a keyword is used to return any value from a method.
Return value will be sent back to method calling statement.
In return value void should not be used because return datatype should be used for storing value.
Return statement should be the last statement in a method definition.

Example:

String buy()
{
System.out.println("buy method");
return "thank you"
}

Variable:

Variable is a container, that used to store the value (or) data.

Local and Global variables:

Local variables are used inside the method.
Global variables are used outside the method.

Datatypes and Variables in JAVA...

Chithra Priya — Mon, 14 Jul 2025 07:40:26 +0000

Datatypes:

Datatypes are used to store the date. Java has two types of datatypes. They are,
1. Primitive datatype
2. Non-primitive datatype

Primitive Datatype:

Primitive datatypes are fixed. They are, Numeric and Non-Numeric.

Numeric type:
1.Byte: 1-byte signed two's complement integer.
2.Short: 2-bytes signed two's complement integer.
3.int: 4-bytes signed two's complement integer. This is the default integer type.
4.long: 8-bytes signed two's complement integer. Used for very large integer values.
5.float: 4-bytes floating-point number. Used for decimal values.
6.double: 8-bytes floating-point number.

Non-Numeric type:
1.char: 2-bytes Unicode character. Used to store single characters.
2.boolean: Represents a logical value, only be true or false.

Non-Primitive Datatypes:

Non-Primitive datatypes are non fixed. They are,

1.strings
2.objects
3.arrays

Variables:

Datatypes are used in variables. There are two types of variables. They are,

1.Inside the method
2.Outside the method

How to declare, initialize and Reassign a variable?

int number; (variable declaration)
number=50; (Initialize)
number=60; (Reassign)

I learned today in Java: Class, Object and Basics of OOP concept

Chithra Priya — Fri, 11 Jul 2025 17:14:43 +0000

What is Class?
Class is a template or blue print.it's group of activity or container.

What is an Object?
Object is a combination of state and behaviour.

What is an OOP?
OOP stands for Object-Oriented Programming Language.

Procedural programming is about writing procedures or methods that perform operations on the data, while object-oriented programming is about creating objects that contain both data and methods.

Advantages of OOP:
OOP is faster and easier to execute
OOP provides a clear structure for the programs
OOP helps to keep the Java code DRY "Don't Repeat Yourself", and makes the code easier to maintain, modify and debug
OOP makes it possible to create full reusable applications with less code and shorter development time.

OOPS Pillars:

Encapsulation:
The meaning of Encapsulation, is to make sure that "sensitive" data is hidden from users. To achieve this, you must:

declare class variables/attributes as private
provide public get and set methods to access and update the value of a private variable.

Inheritance:
An object of one class acting as an object of another class.

Polymorphism:
Polymorphism means "many forms", and it occurs when we have many classes that are related to each other by inheritance.

Abstractions:
Showing only necessary data and hiding unwanted data.

Introduction to JAVA:

Chithra Priya — Thu, 10 Jul 2025 10:03:07 +0000

What is Java?

Java is a high-level, object oriented programming language. It was first introduced in Sun Micro system in 1991. Now owned by oracle corporation. It was designed to be platform independent it means java can run on any device and any operating system that has a Java Virtual Machine(JVM) installed. "Write once, Run anywhere" Approach. Where code written in java can be compiled into bytecode that executed on any system with help of JVM.

Features of Java:

1. Platform Independence: When we write Java code, it is first compiled by the compiler and then converted into bytecode.
This byte code can run on any platform which has JVM installed.

2. Object Oriented: Java follows the object oriented programming

3. Simple and Familiar: Java syntax is inspired by C and C++, making it familiar to many programmers.

4. Robust and Secure: Java has feature like memory management, strong type checking, and exception handling to ensure robust and secure program.

5. Multi-threading: Java supports Multi-threading, allowing multiple tasks to be executed concurrently.

6. Dynamic: Java supports dynamic memory allocation and garbage collection, simplifying memory management.

7. High performance: While java programs might not be as fast as compiled languages like C++. Java performance has improved overtime, thanks to JVM optimizations.

8. Distributed: Java has libraries for creating distributed applications allowing components to communicate over a network.

9. Portable: Java "Write once, Run anywhere" capablity makes it highly portable.

10. Rich Standard library: Java provides a vast standard library for various tasks, from data structures to network communication.

Architecture of Java:

Compiler: Compiler can convert java code to byte code (.java file to .class file) with help of Java development kit(JDK). It translate entire code of the program.

Interpreter: In Java, an interpreter is a program that executes Java bytecode instructions line by line. It's a key component of the Java Virtual Machine (JVM).

Java code Execution process:

JavaScript String Methods()..

Chithra Priya — Fri, 04 Jul 2025 03:26:48 +0000

Today, my mentor taught string methods in JavaScript, and then gave us some tasks to practice.

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <!-- Desc: string to lowercase -->

    <!-- <h1>String Lowercase()</h1>
    <p>JavaScript is the world's most popular programming language</p>
    <button onClick="Lowercase()">Change text</button>
    <div id="Change"></div>

    <script>
        function Lowercase() {
            let text = "JavaScript is the world's most popular programming language";
            document.getElementById("Change").innerText = text.toLocaleLowerCase();
        }
    </script> -->

    <!-- Desc: String concat -->

    <!-- <h1>String Concat()</h1>
    <p>show my name</p>
    <div id="concat"></div>

    <script>
        let text1 = "Chithra";
        let text2 = "Priya";
        let text3 = text1.concat(" ", text2);
        document.getElementById("concat").innerHTML = text3;
    </script>


 <!-- Desc: Strinng Trim  -->

    <!-- <h1>String trim()</h1>
<p id="trim"></p>

<script>
let text1 = "     Hello World!     ";
let text2 = text1.trimStart();
document.getElementById("trim").innerHTML =
"Length text1 = " + text1.length + "<br>Length text2 = " + text2.length;
</script> -->

    <!-- Desc: Trim start -->

    <!-- <h1>The trimStart()</h1>
    <p id="demo"></p>

    <script>
        let text1 = "     chithra priya!     ";
        let text2 = text1.trimStart();
        document.getElementById("demo").innerHTML =
            "Length text1 = " + text1.length + "<br>Length text2 = " + text2.length;
    </script> -->

<!-- Desc: Trim end -->

<!-- <h1>The trimEnd()</h1>
<p id="demo"></p>

<script>
let text1 = "     Chithrapriya     ";
let text2 = text1.trimEnd();
document.getElementById("demo").innerHTML =
"Length text1 = " + text1.length + "<br>Length text2 = " + text2.length;
</script> -->

<!-- Desc: String padStart -->

<!-- <h1>The padStart()</h1>
<p>It pads the string with another string (multiple times) until it reaches a given length.</p>
<p id="demo"></p>

<script>
let text = "5";
text = text.padStart(10,"1");
document.getElementById("demo").innerHTML = text;
</script> -->

Desc: String padEnd

<h1>The padEnd()</h1>
<p>It pads the string with another string (multiple times) until it reaches a given length.</p>
<p id="demo"></p>

<script>
let text = "5";
text = text.padEnd(10,"0");
document.getElementById("demo").innerHTML = text;
</script>

</body>
</html>

Create weather App using API..

Chithra Priya — Wed, 02 Jul 2025 00:18:17 +0000

Today, My mentor teach me how to create a weather-checking app using the OpenWeatherMap URL through an API. Then, we learned how fetch, async/await, and axios work in it.

API: Connecting two different domains.

Fetch():

fetch() is a built-in JavaScript function used to make HTTP requests (like GET, POST) from the browser to a server or an API.
fetch() is used to get or send data from/to APIs.
It returns a Promise
You need to manually convert the response using .json()

Example:

fetch(url)
              .then((res) => {
                     return res.json();
                }).then((data) => {
                     console.log(data.main.feels_like);
                     result.innerHTML = `Temperature : ${data.main.temp}`
                 }).catch((error) => {
                     console.log(error);

                 })

async & await:

async and await are modern keywords used in JavaScript to handle promises more easily and clearly — instead of chaining .then().
They make asynchronous code look like synchronous code, which is easier to read and understand.
You put async before a function to make it return a Promise.
Inside this function, you can use await.
await can only be used inside an async function.
It waits for the promise to resolve before moving to the next line.

Example:

async function getData() {
  let response = await fetch('https://api.example.com/data');
  let data = await response.json();
  console.log(data);
}
getData();

async Makes a function return a promise
await Pauses the async function until the promise resolves

Axois:

A promise-based HTTP client that's simpler and more powerful than fetch.
It works like fetch, but with more features and a simpler syntax.

Example:

import axios from 'axios';

axios.get('https://api.example.com/weather')
  .then(response => console.log(response.data))
  .catch(error => console.log("Error:", error));

Automatically parses JSON.
Axios is a powerful alternative to fetch.
It simplifies HTTP requests.