Java Program to print Prime numbers in Java - Example Tutorial and Code (original) (raw)

How to print Prime numbers in Java or how to check if a number is prime or not is classical Java programming questions, mostly taught in Java programming courses. A number is called a prime number if it's not divisible by any number other than 1 or itself and you can use this logic to check whether a number is prime or not. This program is slightly difficult than printing even or odd numbers which is relatively easier than Java exercises. This Simple Java program prints prime numbers starting from 1 to 100 or any specified number. It also has a method that checks if a number is prime or not.

Code Example to print Prime numbers in Java

Here is a complete sample code example to print prime numbers from 1 to any specified number. This Java program can also check if a number is prime or not as prime number checking logic is encapsulated in the isPrime(int number) method.

import java.util.Scanner;

/** * Simple Java program to print prime numbers from 1 to 100 or any number. * A prime number is a number which is greater than 1 and divisible * by either 1 or itself. */
public class PrimeNumberExample {

public static void main(String args[]) {

//get input till which prime number to be printed
System.out.println("Enter the number till which prime number to be printed: ");
int limit = new Scanner(System.in).nextInt();

//printing primer numbers till the limit ( 1 to 100)
System.out.println("Printing prime number from 1 to " + limit);
for(int number = 2; number<=limit; number++){
//print prime numbers only
if(isPrime(number)){
System.out.println(number);
}
}

}

/* * Prime number is not divisible by any number other than 1 and itself * @return true if number is prime */
public static boolean isPrime(int number){
for(int i=2; i<number; i++){
if(number%i == 0){
return false; //number is divisible so its not prime
}
}
return true; //number is prime now
}
}

Output:
Enter the number till which prime number to be printed:
20
Printing prime numbers from 1 to 20
2
3
5
7
11
13
17
19

In this Java program, we have two-part, the first part which is taking input from the user to print prime numbers, and the other part is function isPrime(int number) which checks whether a number is prime or not. Java method isPrime(int number) can also be used anywhere in code because of its encapsulated logic of checking prime numbers.

There is also another popular Java question is "How to check if a number is prime or not?", isPrime() can be used there. it's rather simple and just implement the logic of prime number in Java i.e. divides a number, starting from 2 till the number itself if it's divisible by another number means it's not prime.

That's all on how to print prime numbers in Java or how to check if a number is prime or not. It's worth remembering logic that when a number is prime and how do you check for prime number. If you are doing homework then get an Idea but type the program yourself, which will give you thinking time on how this Java program is working and checking for prime numbers.

Related Java Program tutorials

And now is the quiz time, What is the time complexity of this algorithm to print prime numbers in Java? can you improve this by using any data structure or different approach?

Also what is your favorite coding exercise? Palindrom, Prime number or Reverse a given String in Java?