## What is a Prime Number?

A prime number is a number that is only divisible by 1 or itself. For example, 11 is only divisible by 1 or itself. Other Prime numbers 2, 3, 5, 7, 11, 13, 17… *(Source: Guru99)*

**Note**: 0 and 1 are not prime numbers. 2 is the only even prime number.

Java Program to display prime numbers from 1 to 100

**Program Logic**:

- The main method contains a loop to check prime numbers one by one.
- The main method calls the method CheckPrime to determine whether a number is prime
- We need to divide an input number, say 17 from values 2 to 17 and check the remainder. If the remainder is 0 number is not prime.
- No number is divisible by more than half of itself. So, we need to loop through just numberToCheck/2. If the input is 17, half is 8.5, and the loop will iterate through values 2 to 8
- If numberToCheck is entirely divisible by another number, we return false, and loop is broken.
- If numberToCheckis prime, we return true.
- In the main method, check isPrime is TRUE and add to primeNumbersFound String
- Lastly, print the results

```
public class primeNumbersFoundber {
public static void main(String[] args) {
int i;
int num = 0;
int maxCheck = 100; // maxCheck limit till which you want to find prime numbers
boolean isPrime = true;
//Empty String
String primeNumbersFound = "";
//Start loop 1 to maxCheck
for (i = 1; i <= maxCheck; i++) {
isPrime = CheckPrime(i);
if (isPrime) {
primeNumbersFound = primeNumbersFound + i + " ";
}
}
System.out.println("Prime numbers from 1 to " + maxCheck + " are:");
// Print prime numbers from 1 to maxCheck
System.out.println(primeNumbersFound);
}
public static boolean CheckPrime(int numberToCheck) {
int remainder;
for (int i = 2; i <= numberToCheck / 2; i++) {
remainder = numberToCheck % i;
//if remainder is 0 than numberToCheckber is not prime and break loop. Elese continue loop
if (remainder == 0) {
return false;
}
}
return true;
}
}
```

**Output**:

```
Prime numbers from 1 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 97
```