Java Program To Check Prime Number using While Loop

In this java program, we check whether the user input number is prime or not.

Program :

import java.util.Scanner;

public class PrimeChecWhile 

    {

        public static void main(String[] args)

        {

            int temp;

            boolean isPrime = true;

            Scanner sc = new Scanner(System.in);

            System.out.println("Enter any number:");

            //capture the input in an integer

            int num = sc.nextInt();

            sc.close();

            int i = 2;

            while(i<=num/2)

            {

                if(num%i==0)

                {

                    isPrime = false;

                    break;

                }

                i++;

            }

            //If isPrime is true then the number is prime else not

        if(isPrime)

        System.out.println(num+"is a Prime Number");

        else

        System.out.println(num+"is not a Prime Number");

        }

        }

Java Program To Check Prime Number

In this java program, we check whether the user input number is prime or not.

Program :

import java.util.Scanner;

public class PrimeChec 

    {

        public static void main(String[]args)

        {

            int temp;

            boolean isPrime = true;

            Scanner sc = new Scanner(System.in);

            System.out.println("Enter any number:");

            //capture the input in an integer

            int num = sc.nextInt();

            sc.close();

            for(int i=2; i<=num/2; i++)

            {

                temp = num%i;

                if(temp==0)

                {

                    isPrime=false;

                    break;

                }

            }

            //If isPrime is true then the number is prime else not

            if(isPrime)

                System.out.println(num + "is a Prime Number");

            else

                System.out.println(num + "is not a Prime Number");  

        }

}

Java Program To Break Integer into Digits

In this Java Program, we break Integers into Digits

Here we use Scanner class to get input from the user. First While loop is use to count the digits in the input number and second while loop is use to extract the digits from the input number using modulus operator.

Step 1 : Import Scanner Class

Step 2 : Create a Class IntegerToDigit

Step 3 : Create main method

Step 4 : Initialize num, temp, digit and count and store 0 in count

Step 5 : Ask the user to enter any number

Step 6 : Store the user entered number into num variable

Step 7 : Close the Scanner class to avoid memory leaks

Step 8 : Create a copy of input number

Step 9 : Store the num into temp

Step 10 : Count the digits into the input number

Step 11 : Apply While loop where num is greater than zero

Step 12 : Divide num by 10 and store the result into num variable

Step 13 : Increment count by one.

Step 14 : Apply another while loop where temp is greater than zero and store the result of temp % 0 into digit.

Step 15 : Print the Digit

Step 16 : Divide temp by 10 and store the result into temp variable

Step 17 : Decrement count by one.

Program :

import java.util.Scanner;

public class IntegerToDigit {

    public static void main(String[]args)

    {

        int num, temp, digit, count = 0;

        //getting the number from user

        Scanner sc = new Scanner(System.in);

        System.out.print("Enter any number:");

        num = sc.nextInt();

        sc.close();

        //creating a copy of the input number

        temp = num;

        //counting digits int the input number

        while(num > 0)

        {

            num = num / 10;

            count++;

        }

        while(temp > 0)

        {

            digit = temp % 10;

            System.out.println("Digit at place "+count+" is:"+digit);

            temp = temp / 10;

            count --;      

        }

    }    

}

Output :

Enter any number:7891

Digit at place 4 is:1

Digit at place 3 is:9

Digit at place 2 is:8

Digit at place 1 is:7

For execution of the same do visit my YouTube Channel :

https://youtu.be/yYfE4xFPj4s

Java Program To Find The Factorial Of A Number Using Recursion

In this Java Program, we calculate the factorial of the number using recursion.

Factorial of n is the product of all the positive descending integers. It is denoted by n!

For example : 4! = 4 * 3 * 2 * 1 = 24

Logic : fact = fact * i;

Step 1 : Create main method

Step 2  : Create variable factorial and store factorial of 4 in it.

Step 3  : Print the number

Step 4 : Create a static function which returns 1

Step 5 : Create recursion function which calls itself

Program :

public class FactorialDemo2 {

    public static void main(String[] args){

        int factorial = fact(4);

        System.out.println("Factorial of 4 is:"+factorial);

    }

    static int fact(int n)

    {

    int output;

    if(n==1){

        return 1;

    }

    //Recursion : Function calling itself

    output = fact(n-1)*n;

    return output;

    }

}

Output :

Factorial of 4 is : 24

For execution of the same do visit my YouTube Channel :

https://youtu.be/xGJ2VBxZuRc

Java Program To Find The Factorial Of A Number Using Recursion Entered By The User

In this Java Program, we calculate the factorial of the number using recursion entered by the user.

Factorial of n is the product of all the positive descending integers. It is denoted by n!

For example : 4! = 4 * 3 * 2 * 1 = 24

Logic : fact = fact * i;

Step 1 : Import Scanner Class

Step 2 : Create main method

Step 3 : Create scanner object for capturing the user input

Step 4 : Ask the user to enter the number

Step 5 : Store the entered value in the variable num

Step 6 : Call the user defined function fact

Step 7 : Print the number

Step 8 : Create a static function which returns 1

Step 9 : Create recursion function which calls itself

Program :

import java.util.Scanner;

public class FactorialDemo {

    public static void main(String[] args)

    {

        //Scanner object for capturing the user input

        Scanner sc = new Scanner(System.in);

        System.out.println("Enter the number:");

        //Store the entered value in variable

        int num =sc.nextInt();

        //Call the user defined function fact

        int factorial = fact(num);

        System.out.println("Factorial of entered number is:"+factorial);

    }

    static int fact(int n)

    {

        int output;

        if(n==1){

            return 1;

        }

                //Recursion: Function calling itself

        output = fact(n-1)*n;

        return output;

    }    

}

Output :

Enter the number:

5

Factorial of entered number is:120

For execution of the same do visit my YouTube Channel :

https://youtu.be/IBSxhMDbMrw

Java Program To Reverse a String Entered by the User

In this Java Program, we reverse a string entered by the user

Logic :  String reversed = reverseString(str);

Step 1 : Import Scanner Class

Step 2 : Create main method

Step 3 : Create variable str

Step 4 : Ask user to enter the username

Step 5 : Create the object of the Scanner Class

Step 6 : Store the user entered username in the variable str

Step 7 : Close the scanner class to avoid memory lea

Step 8 : Apply the logic

Step 9 : Print the reversed string

Step 10 : Create reversedString method

Step 11 : Apply if condition which says if str is empty then reverse string

Step 12 : Call the function recursively 

Program :

import java.util.Scanner;

public class JavaExample2 {

    public static void main(String[] args)

    {

        String str;

        System.out.println("Enter your username:");

        Scanner sc = new Scanner(System.in);

        str = sc.nextLine();

        sc.close();

        String reversed = reverseString(str);

        System.out.println("The reversed string is:"+reversed);

    }

    public static String reverseString(String str)

    {

        if(str.isEmpty())

            return str;

        //calling function recursively

        return reverseString(str.substring(1))+str.charAt(0);

    }

}

Output :

Enter your username:

how are you doing?

The reversed string is:?gniod uoy era woh

For execution of the same do visit my Youtube Channel :

https://youtu.be/GUoz8dR5d1E

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