Java Program to find the largest prime factor

     A number which is divided by itself and 1 is called Prime number. Prime factors consist of prime numbers which are the multiplied to generate the original number.

Eg:

45 =3X3X5

Largest prime factor is5.

Let us implement this concept in java.

Steps to follow:

• A public class LargestPrimeFactorEg is generated with constructor LargestPrimeFactorEg().
• The constructor gets an input as the number.
• Two long variables are declared with initial values.
• One is for largestfactor(largeFactor) and another one is for divisor(div).
• A while loop is created with the condition the number is greater than one.
• Using % operator,the remainder is checked with zero. If so, largefactor is set to divisor value.
• The no value is divided by divisor and stored it in no.
• Again, in the another while loop,no % divisor value is equal to zero, no is divided by divisor and it is assigned to no.
• Increment the divisor value by 1.
• Repeat this process until the condition fails.
• Finally return the largest factor value to the main function.
• In the main() function, read the input as no from the user.
• Call the largestPrimeFactorEg() function.
• Get the returned value from the function and print it to the output screen.

Program:

import java.util.Scanner;

//public class with constructor

public class LargestPrimeFactorEg {

    public static long largestPrimeFactorEg(long no) {

        long largeFactor = 1;

        long div = 2;

        while (no > 1) {

            if (no % div == 0) {

                largeFactor = div;

                no /= div;

                while (no % div == 0) {

                    no /= div;

                }

            }

            div++;

        }

        return largeFactor;

    }

//main() function

    public static void main(String[] args) {

        Scanner myObj1 = new Scanner(System.in);

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

        long no = myObj1.nextLong();

        System.out.println("The Largest prime factor of the given number: " + largestPrimeFactorEg(no));

    }

}

Output:

C:\raji\blog>javac LargestPrimeFactorEg.java

C:\raji\blog>java LargestPrimeFactorEg

Enter the number

56

The Largest prime factor of the given number: 7

C:\raji\blog>java LargestPrimeFactorEg

Enter the number

765

The Largest prime factor of the given number: 17

This is the java Program to find the largest prime factor. Keep coding!!!!