Hi all, hope you are doing good.

In general we think that, finding prime number will be very easy and normally we neglect to refresh this program before attending interview. Even though concepts are same Interviewer may ask same program in many ways. So be prepared while attending interview. Hope below article will clear about possible way of ask to check prime number.

## About Prime Number

Prime number is a number that is greater than 1 and divided by 1 or itself only. Note that, prime numbers can’t be divided by other numbers than itself or 1.

For example, Prime number from 0 to 100 are, 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, and 97. **Note:**

- 0 or 1 is not Prime Number.
- 2 is Prime number

### Example 1: Check given number is Prime or not

import java.util.Scanner; public class PrimeNumber { public static void main(String[] args) { //Create object for scanner class to fetch input data from keyboard Scanner scn = new Scanner(System.in); System.out.print("Please enter input value:"); int inputValue = scn.nextInt(); boolean flag = false; if (inputValue == 0 || inputValue == 1) { System.out.println(inputValue+ " is neither PRIME nor COMPOSITE number"); } else { for (int i = 2; i <= inputValue / 2; i++) { if (inputValue % i == 0) { flag = true; break; } } if (!flag) System.out.println(inputValue+ " is a Prime number"); else System.out.println(inputValue+ " is NOT a Prime number"); } } }

```
Output 1:
Please enter input value:1
1 is neither PRIME nor COMPOSITE number
Output 2:
Please enter input value: 2
2 is a Prime number
Output 3:
Please enter input value: 17
17 is a Prime number
Output 4:
Please enter input value: 25
25 is NOT a Prime number
```

### Example 2: Check given range of number is Prime or not

import java.util.Scanner; public class PrimeNumberRange { public static void main(String[] args) { //Create object for scanner class to fetch input data from keyboard Scanner scn = new Scanner(System.in); System.out.print("Enter range : "); int range = scn.nextInt(); if (range == 0 || range == 1) { System.out.println("Given range is not valid, Please try again !"); }else{ System.out.println("Prime numbers are: "); for (int inputValue = 0; inputValue <=range; inputValue++) { if (inputValue == 0 || inputValue == 1) { continue; } else { boolean flag = false; for (int i = 2; i <= inputValue / 2; i++) { if (inputValue % i == 0) { flag = true; break; } } if (!flag) { System.out.println(inputValue); } } } } } }

```
Output 1:
Enter range : 0
Given range is not valid, Please try again !
Output 2:
Enter range : 2
Prime numbers are:
2
Output 3:
Enter range : 10
Prime numbers are:
2
3
5
7
Output 4:
Enter range : 25
Prime numbers are:
2
3
5
7
11
13
17
19
23
```

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- Introduction to java
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- Sort an array in ascending, descending order in java

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