# Check if a number is prime number in Java Example

This example shows how to check if a number is prime number in Java. This example also shows how to find prime numbers between 1 and 100 or between any two numbers.

## What is a prime number?

Definition of a prime number from Wikipedia,

A prime number (or a prime) is a natural number greater than 1 that has no positive divisors other than 1 and itself.

## How to check if a number is a prime number in Java?

If we cannot divide a number (greater than 1) by any positive number other than 1 or itself, then the number is a prime number. We will use the modulus operator (%) to check if we can divide the number as given below.

Output

As you may have observed from the above code, the for loop inside the `isPrimeNumber` method goes only up to number/2. That is because any number cannot be perfectly divided by anything above the half of that number.

## How to find the prime numbers between 1 and 100?

We will do a slight modification to the above program to find prime numbers between 1 and 100 as given below.

Output

Here, we have introduced a new loop that goes through 2 to 100 and checks the number one by one. The inner loop goes from 2 to half of the number and tries to divide the number. If a reminder of any of the divisions is zero then the number is not a prime number.

## How to find all prime numbers between 1 to n?

In the above example, we printed prime numbers between 1 and 100. Now, we are going to take input from the user using the Scanner and print the prime numbers between 2 and the input number as given below.

Output

This example is a part of the Java Basic Examples. 