# Java – Print Prime numbers between specified range

In this article, we will write a simple Java program to print Prime numbers between the specified range or interval

# 1. Prime Number programs

• A number is Prime number which is divisible by 1 or itself only
• 0 & 1 aren’t Prime Numbers
• 2 is the only Even Prime number
• We will print Prime numbers between specified range/interval using 2 different loops,
1. using for loop
2. using while loop

## 1.1 Using for loop

We will iterate through for-loop to find prime numbers for the specified range and invoke method for each numbers and it does the following task,

• Initially we will declare a flag isPrime and set to true assuming given number is prime
• Iterate using for-loop,
• starting from 2
• up to given number/2
• increment by 1 in every iteration
• During iteration inside for-loop, we will check whether remainder is zero by modulo of given number by iterating numbers from 2 till given number/2
• If condition succeeds then set the flag to false and break the for-loop i.e., given number is not Prime number
• Finally, returning isPrime flag to calling method to print to console

```package in.bench.resources.numbers;

// main() method
public static void main(String[] args) {

System.out.println("Prime numbers between 1 & 100 :- \n");

// find prime numbers between 1 and 100
for(int num = 1; num <= 100; num++) {

// check prime or not
if(checkPrimeOrNot(num)) {
System.out.print(num + " ");
}
}
}

/**
* This method checks whether input number is prime or Not using for loop
*
* - 0 & 1 aren't Prime Numbers
* - 2 is the only EVEN Prime number
* - All even numbers are Prime numbers
* - Prime number is divisible by itself or 1
*
* @param number
* @return
*/
public static boolean checkPrimeOrNot(int number) {

// local variable
boolean isPrime = true;

// Numbers 0 & 1 aren't Prime Numbers
if(0 == number || 1 == number) {

System.out.println("Numbers 0 & 1 aren't Prime Numbers");
isPrime = false;
}
else {

// iterate between 2 & number/2
for(int i=2; i <= number / 2; i++) {

if(number % i == 0) {
isPrime = false;
break;
}
}
}

// return
return isPrime;
}
}
```

Output:

```Prime numbers between 1 & 100 :-

Numbers 0 & 1 aren't Prime Numbers
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
```

## 1.2 Using while loop

We will iterate through while-loop to find prime numbers for the specified range and invoke method for each numbers and it does the following task,

• Initially we will declare a flag isPrime and set to true assuming given number is prime
• Declare another variable i of type integer with initial value of 2
• Iterate using while-loop, by checking whether the value of i is less-than or equal-to number/2
• During iteration inside while-loop, we will check whether remainder is zero by modulo of given number by iterating numbers from 2 till given number/2 and also increment variable i by 1 in every iteration at the end
• If condition succeeds then set the flag to false and break the while-loop i.e., given number is not Prime number
• Finally, returning isPrime flag to calling method to print to console

```package in.bench.resources.numbers;

// main() method
public static void main(String[] args) {

int num = 100;

System.out.println("Prime numbers between 100 & 199 :- \n");

// find prime numbers between 100 and 199
while(num <= 199) {

// check prime or not
if(checkPrimeOrNot(num)) {
System.out.print(num + " ");
}

// increment num by 1
num++;
}
}

/**
* This method checks whether input number is prime or Not using while loop
*
* - 0 & 1 aren't Prime Numbers
* - 2 is the only EVEN Prime number
* - All even numbers are Prime numbers
* - Prime number is divisible by itself or 1
*
* @param number
* @return
*/
public static boolean checkPrimeOrNot(int number) {

// local variable
int i = 2;
boolean isPrime = true;

if(0 == number || 1 == number) {

System.out.println("Numbers 0 & 1 aren't Prime Numbers");
isPrime = false;
}
else {

while(i <= number / 2) {

if(number % i == 0) {
isPrime = false;
break;
}

// increment value by 1
i++;
}
}

// return
return isPrime;
}
}
```

Output:

```Prime numbers between 100 & 199 :-

101 103 107 109 113 127 131 137 139 149 151 157 163 167 173 179 181 191 193 197 199
```

Happy Coding !!
Happy Learning !!