Java Program to Display Prime Numbers Between Intervals Using Function

Introduction

Prime numbers, those greater than 1 with no divisors other than 1 and themselves, are a fundamental concept in mathematics and computer science. Identifying prime numbers within a specific range involves checking if numbers within that range have any divisors other than 1 and themselves. This task can provide a practical grasp of loops and conditionals in programming.

In this article, you will learn how to create a Java program to display prime numbers between two given intervals using functions. The examples will demonstrate how to define a function for checking primality and utilize this function to filter and print prime numbers within a specified range.

Displaying Prime Numbers Between Intervals

Defining the Prime-checking Function

1. Start by defining a function named isPrime that takes an integer number as its parameter. This function will return true if the number is a prime and false otherwise.

2. Ensure the function handles edge cases, such as numbers less than 2, which are not prime by definition.

   java Copy

   public static boolean isPrime(int number) {
       if (number <= 1) {
           return false;
       }
       for (int i = 2; i <= Math.sqrt(number); i++) {
           if (number % i == 0) {
               return false;
           }
       }
       return true;
   }
   

   Explain Code

   This function starts by discarding any number less than or equal to 1. It then checks every number up to the square root of number for divisibility. If any divisor is found, it returns false; otherwise, it returns true.

Creating the Main Function to Display Primes

1. Define the main method where you prompt the user to enter the interval limits - start and end.

2. Loop through the range from start to end, and use the isPrime function to check each number. If it is prime, print the number.

   java Copy

   import java.util.Scanner;
   
   public class PrimeNumbersBetweenIntervals {
       public static void main(String[] args) {
           Scanner scanner = new Scanner(System.in);
           System.out.print("Enter the start of the interval: ");
           int start = scanner.nextInt();
           System.out.print("Enter the end of the interval: ");
           int end = scanner.nextInt();
   
           System.out.printf("Prime numbers between %d and %d are:%n", start, end);
           for (int i = start; i <= end; i++) {
               if (isPrime(i)) {
                   System.out.println(i);
               }
           }
   
           scanner.close();
       }
   }
   

   Explain Code

   In this code, Scanner is used to collect integer inputs for start and end. The program then iterates from start to end, printing each number that isPrime identifies as a prime.

Conclusion

The program you've just explored effectively displays prime numbers between user-defined intervals using a dedicated function to determine primality. Through this exercise, you enhance your understanding of functions, loops, and conditionals in Java. Incorporate this logic into broader applications where understanding and manipulating prime numbers are crucial. By following the outlined steps and explanations, you ensure your Java programming skills remain sharp and efficient in tackling various algorithmic challenges.