 # Java Program to check whether a number is prime or not

Here we are explaining how to write a java program to check whether a number is prime or not.

## What is a prime number?

A prime number is a number that can be exactly divided by 1 and that number itself.

Example:2 , 3 ,5, 7 etc.

Here 2 is divided by 1 and 2.

3 is divided by 1 and 3.

5 is divided by 1 and 5.

## How to implement the java program to check whether a number is prime or not?

First, we have to declare the class PrimeNumber with a public modifier. Create an object of the scanner class as sc and read the integer number from the user into the variable num. Create a boolean variable flag and set it to false. By using a `for loop`, set i=2and check iN=num/2, Then check the condition for prime, that is check num mod i equals 0 or not. If it equal to zero then set flag=true and break. `If` flag not equals true, then display it as a prime number, `else` display it as not a prime number using `System.out.println()` function.

## ALGORITHM

STEP 1: Declare the class PrimeNumber with a public modifier.

STEP 2: Open the main() to start the program, Java program execution starts with the main()

STEP 3: Read the number from the user into the variable num.

STEP 4: Declare flag as boolean variable and set to false.

STEP 5: By using a `for loop` set i=2,check i<=num/2,do step 6.

STEP 6: check if num mod i equals o or not, if it equal to zero then set flag=true and break.

STEP 7: Check if the flag not equal to true then display a number as a prime number.

STEP 8: Else display the number is not a prime number.

## Java Source Code

```                                          ```import java.util.Scanner;

public static void main(String[] args) {

Scanner sc = new Scanner(System.in);

System.out.println("Enter the Number: ");
int num= sc.nextInt();
boolean flag = false;
for(int i = 2; i <= num/2; ++i)
{

if(num % i == 0)
{
flag = true;
break;
}
}

if (!flag)
System.out.println(num + " Is A Prime Number");
else
System.out.println(num + " Is Not A Prime Number");
}
}```
```

## OUTPUT

```Enter the Number: 7
7 Is A Prime Number```
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