DEV Community: AmalaReegan

Day 28-Factorial Number:

AmalaReegan — Mon, 31 Mar 2025 11:40:11 +0000

Factorial:

==> Factorial of a non-negative integer, is multiplication of all integers smaller than or equal to n

Example Program:

package day1;

import java.util.Scanner;
public class Factorial
{
public static void main(String[] args)
{
Scanner scan=new Scanner(System.in);
System.out.println("Enter the factorial number");
int n=scan.nextInt();
long Factorial=1;
for(int i=1; i<=n; i++)
{
Factorial=Factorial*i;
}
System.out.println(Factorial);
}
}

Output:

Day 27-Java collections:

AmalaReegan — Wed, 26 Mar 2025 03:12:41 +0000

Collections of java:

==> Java Collections are a framework that provides a set of classes and interfaces to store and manipulate data in Java.

==> The Java Collections Framework is a part of the java.util package and is designed to handle groups of objects.

There are two main types of collections in Java:

==> Collection Interface
==> Map Interface

1.Collection Interface:

List:

==> An ordered collection that can contain duplicate elements.

ArrayList:

==> A dynamic array that grows as needed. Elements can be accessed by index.

LinkedList:

==> Doubly linked list. It allows for fast insertions/deletions at both ends but is slower for random access.

Set:

==> A collection that does not allow duplicates.

HashSet:

==> No duplicates and does not maintain any order.

LinkedHashSet:

==> No duplicates, but it maintains insertion order.

TreeSet:

==> No duplicates, and it orders elements according to their natural ordering or a comparator.

Queue:

==> A collection used for holding elements prior to processing.

PriorityQueue:

==> A queue where elements are processed in order of their priority.

LinkedList:

==> Implements both List and Queue interfaces.

2.Map Interface

==> This is not a true collection but a structure that holds key-value pairs, where each key maps to exactly one value.

HashMap:

==> A map that does not maintain any order of keys.

LinkedHashMap:

==> A map that maintains the insertion order of keys.

TreeMap:

==> A map that maintains keys in sorted order.

Example:

import java.util.*;

public class CollectionExample {
    public static void main(String[] args) {

        // List Example (Allow Duplicates)
        List<String> list = new ArrayList<>();
        list.add("Java");
        list.add("Python");
        list.add("Java");
        System.out.println("List: " + list);

        // Set Example (No Duplicates)
        Set<String> set = new HashSet<>();
        set.add("Java");
        set.add("C++");
        set.add("Java");
        System.out.println("Set (No Duplicates): " + set);

        // Map Example (Key-Value pairs)
        Map<String, Integer> map = new HashMap<>();
        map.put("Java", 8);
        map.put("Python", 3);
        map.put("JavaScript", 6);
        System.out.println("Map: " + map);

        // Queue Example
        Queue<String> queue = new LinkedList<>();
        queue.add("First");
        queue.add("Second");
        queue.add("Third");
        System.out.println("Queue: " + queue);
    }
}

Output:

List: [Java, Python, Java]
Set (No Duplicates): [Java, C++]
Map: {Java=8, Python=3, JavaScript=6}
Queue: [First, Second, Third]

Day26.1 - Searching in java: Binary search

AmalaReegan — Mon, 24 Feb 2025 18:26:45 +0000

Binary Search:

Definition:

Binary search oru efficient algorithm,ithu sorted array la oru element ah thedura method.Divide and conquer approach use pannum athu search range ah rendu panga pirichu (half ah divide pannitu) check pannum.

Time Complexity:

Best case:

O(1) — target middle la irundha first check la kandupidichurum

Worst and Average case:

O(log n) — because every time, search space ah half pannitu pogum. Adhan logarithmic time complexity.

Condition:

Array must be sorted — Binary search unsorted arrays la work agadhu!So,ascending or descending order la irukkanum data.

Simple Definition:

Middle element ah check panni,target smaller ah irundha left side la pogum,target bigger ah irundha right side la pogum ippadi half half ah split pannitu search pannum.

Example Program:

package javaprogram;

public class Binarysearch {
public static void main(String[] args) 
{

// TODO Auto-generated method stub

int[]arr={10,15,20,25,30,35,40,45}; 
         //0 ,1 ,2 ,3 ,4 ,5 ,6 ,7

int key=40;
int min_index=0;
int max_index=arr.length-1;
while(min_index<=max_index)
{
int mid_index=(min_index+max_index)/2;  //3
if(arr[mid_index]==key)
{
System.out.println("key is presented in "+ mid_index);
break;
}
else if (key>arr[mid_index]) //3
{
min_index = mid_index+1;   //3+1=4
//System.out.println("key is presented in "+min_index);
}
else if(key>arr[mid_index]) 
{
min_index = mid_index -1;
System.out.println("key is presented in "+min_index);
}
}
}
}

Output:

Day26 - Searching in java: (Linear Search or (Sequential Search in Java)

AmalaReegan — Mon, 24 Feb 2025 08:46:07 +0000

searching in java:

==> In Java,searching refers to the process of finding an element in a data structure like an array,list,or map.

==> Let’s break down the main types of searching techniques:

Linear Search (Sequential Search):

Definition:

==> Linear search is a simple search algorithm where each element is checked one by one until the target is found or the end of the array is reached.

Time Complexity:

Best case:

==> O(1) — if the target is at the first index.

Worst case:

==> O(n) — if the target is at the last index or not found.

Use case:

==> Works well for small or unsorted datasets.

Example program:(While loop)

package javaprogram;

public class Linearsearch {

public static void main(String[] args) {
// TODO Auto-generated method stub

int[] arr= {10,15,8,11,55,67,7}; //0 1 2 3 4 5 6
int key=7;
int ke=8;
int i=0;

while(true)   //looping  // while(i<arr.length)  
{
if(arr[i]==key)   // if condition
{
System.out.println("key is presented:"+""+i);  //print statement
break;
}

if(arr[i]==ke)    // if condition
{
System.out.println("ke is presented:"+""+i);  //print statement
//break;
}
i++;
}
}
}

Output:

Ex program:

package javaprogram;

public class Linearsearch1 {
public static void main(String[] args) {

// TODO Auto-generated method stub

int[] arr= {10,15,8,11,55,67,7}; //0 1 2 3 4 5 6
int key=7;
if(arr[0]==key)

{
System.out.println("key is presented"+" "+ 0);  //print statement

}
if (arr[1]==key)
{
System.out.println("key is presented"+" "+ 1);
}
if (arr[2]==key)
{
System.out.println("key is presented"+" "+ 2);
}
if (arr[3]==key)
{
System.out.println("key is presented"+" "+ 3);
}
if (arr[4]==key)
{
System.out.println("key is presented"+" "+ 4);
}
if (arr[5]==key)
{
System.out.println("key is presented"+" "+ 5);
}
if (arr[6]==key)
{
System.out.println("key is presented"+" "+ 6);
}
}
}

Output:

Day25

AmalaReegan — Mon, 24 Feb 2025 07:04:22 +0000

Day24-Scanner Class in Java

AmalaReegan — Wed, 19 Feb 2025 04:25:37 +0000

Scanner Class in Java:

==> Scanner is a class in java.util package used for obtaining the input of the primitive types like int, double,and strings.

==> Using the Scanner class in Java is the easiest way to read input in a Java program, though not very efficient if you want an input method for scenarios where time is a constraint like in competitive programming.

Example program:

package javaprogram;

import java.util.Scanner; // Import Scanner class

public class ScannerClass {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);

// Taking String input
System.out.print("Enter your name: ");
String name = scanner.nextLine();

// Taking integer input
System.out.print("Enter your age: ");
int age = scanner.nextInt();

// Displaying input values
System.out.println("Hello, " + name + "! You are " + age + " years old.");

    }
}

Output:

Day23

AmalaReegan — Wed, 19 Feb 2025 04:17:41 +0000

Day22

AmalaReegan — Wed, 19 Feb 2025 04:17:23 +0000

Day21

AmalaReegan — Wed, 19 Feb 2025 04:16:29 +0000

Day20:Quotient And Remainder in Java;

AmalaReegan — Wed, 12 Feb 2025 18:06:19 +0000

Quotient And Remainder:

==> The remainder is the integer left over after dividing one integer by another. The quotient is the quantity produced by the division of two numbers.

For example:

==> (7/2) = 3 In the above expression 7 is divided by 2, so the quotient is 3 and the remainder is 1.

Approach:

==> Divide the dividend by the divisor using / operator. Both dividend and divisor can be of any type except string, the result will also be computed accordingly.

==> Get the remainder using % operator. Expressions used in program to calculate quotient and remainder:

Example Program:

package javaprogram;

public class Remainder {

   public static void main(String[] args) 
  {
    // TODO Auto-generated method stub

   int dividend = 555, divisor = 10;
   while (dividend > 4) {
   int remainder = dividend % divisor;
   System.out.println("The Remainder is = "+ remainder);
   // Reduce the dividend by removing the last digit
   dividend=dividend/divisor;
  }
  }
  }

Output:

The Remainder is = 5
The Remainder is = 5
The Remainder is = 5

Day19:Number Series

AmalaReegan — Tue, 11 Feb 2025 04:36:42 +0000

Task1:

1 . Look at this series: 58, 52, 46, 40, 34,28 ... What number should come next?

Ans:

The series is decreasing by 6 each time:

58-6=52
52-6=46
46-6=40
40-6=34
34-6=28

So, continuing the pattern,28-6=22.
The next number in the series is 22.

Program:

package javaprogram;

public class number {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int num=58;
        int count=1;
        while(count<=7) {
            System.out.println(num);
            num=num-6;
            count=count+1;
        }


    }

}

Output:

2.Look at this series: 3, 4, 7, 8, 11, 12,15,16,19 ... What number should come next?

Ans:

Let’s look at the pattern:
3->4 (add1)
4->7 (add3)
7->8 (add1)
8->11(add3)
11->12(add1)
12->15(add3)
15->16(add1)
16->19(add3)

It looks like the pattern alternates between adding 1 and adding

Following this pattern, the next step is to add 3 to 12, so:

19+1=20

The next number in the series is 20.

Program:

package javaprogram;

public class Numberseries1 {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int num=3;
        int count=1;
        while(count<=10) {
            System.out.println(num);
            num=num+1;
            System.out.println(num);
            num=num+3;
            count=count+2;

        }

    }

}

Output:

3.Look at this series: 1.5, 2.3, 3.1, 3.9, 4.7, 5.5, 6.3,... What number should come next?

4.2

4.4

4.7

5.1

Ans:
Let’s examine the differences between the numbers in the series:

1.5 + 0.8 = 2.3
2.3 + 0.8 = 3.1
3.1 + 0.8 = 3.9
3.9 + 0.8 = 4.7
4.7 + 0.8 = 5.5
5.5 + 0.8 = 6.3

It looks like the series increases by 0.8 each time. So, to find the next number:
6.3 + 0.8 = 7.1
The next number in the series is 7.1.

Program:

package javaprogram;

public class floattask {

public static void main(String[] args) {
// TODO Auto-generated method stub
float no=1.5f;
int count=1;
while(count<=8) {
System.out.println(no);
no=no+0.8f;
count=count+1;
}
}
}

Output:

Day18; Control flow statement

AmalaReegan — Fri, 07 Feb 2025 04:27:36 +0000

Control flow statement:

==> Control flow statements are fundamental components of programming languages that allow developers to control the order in which instructions are executed in a program.

==> They enable execution of a block of code multiple times, execute a block of code based on conditions, terminate or skip the execution of certain lines of code, etc.

Types of Control Flow statements:

Looping Statements:

==> Looping statements, also known as iteration or repetition statements, are used in programming to repeatedly execute a block of code.

==> They are essential for performing tasks such as iterating over elements in a list, reading data from a file, or executing a set of instructions a specific number of times. Here are some common types of looping statements:

1.For loop
2.While loop
3.Do while loop

While loop:

==> Java while loop is a control flow statement used to execute the block of statements repeatedly until the given condition evaluates to false.

==> Once the condition becomes false, the line immediately after the loop in the program is executed.

Syntax:

while (condition) {
// Code to be executed
}

==> The condition is evaluated before each iteration.
==> If the condition is true, the loop executes the block of
code.
==> If the condition is false, the loop stops.

Example:Printing number from 1 to 10:

package javaprogram;

public class Whileloop {
    public static void main(String []args)
    {
    int num=1;
    while(num<10)
    {
    System.out.println(num);
    num=num+1;
    }
    }
}

Output:

Task1:

Example Program:

package javaprogram;

public class task {

public static void main(String[] args) {
    // TODO Auto-generated method stub
    int count=5;
    while(count<=20)
    {
        count=count+3;
        System.out.println(" count:"+count);
    }


}

}

Output:

count:8
count:11
count:14
count:17
count:20
count:23

Task2:

Example program:

package javaprogram;

public class welcome {
public static void main(String[] args) {
int count=1;
while(count<=10) {
System.out.println("welcome to java");
count=count+1;
}

}
}

Output:

welcome to java
welcome to java
welcome to java
welcome to java
welcome to java
welcome to java
welcome to java
welcome to java
welcome to java
welcome to java

Refernce:

https://www.w3schools.com/java/java_while_loop.asp
https://www.geeksforgeeks.org/java-while-loop-with-examples/
https://www.geeksforgeeks.org/control-flow-statements-in-programming/
https://www.codingem.com/flowchart-loop/