Java Program to find Composite Number

Posted in Java Tutorial

Updated on Jan 11, 2024

By Mari Selvan

👁️ 532 - Views

⏳ 4 mins

💬 1 Comment

Photo Credit to CodeToFun

🙋 Introduction

In the realm of programming, identifying and working with different types of numbers is a fundamental skill.

A composite number is one that has more than two positive divisors, excluding 1 and itself. In this tutorial, we'll explore a java program that efficiently determines whether a given number is composite or not.

📄 Example

Let's dive into the java code that checks whether a number is composite or not.

CompositeNumberChecker.java

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import java.util.Scanner;

public class CompositeNumberChecker {

  // Function to check if a number is composite
  static boolean isComposite(int num) {
    if (num <= 1) {
      return false;
    }

    for (int i = 2; i <= Math.sqrt(num); i++) {
      if (num % i == 0) {
        return true; // Found a divisor other than 1 and itself
      }
    }

    return false; // No divisors other than 1 and itself
  }

  // Driver program
  public static void main(String[] args) {
    Scanner scanner = new Scanner(System.in);

    // Default input value is 12
    int number = 12;

    // Call the function to check if the number is composite
    boolean result = isComposite(number);

    // Display the result
    if (result) {
      System.out.println(number + " is a composite number.");
    } else {
      System.out.println(number + " is not a composite number.");
    }

    scanner.close();
  }
}

💻 Testing the Program

To test the program with different numbers, modify the value of the number variable in the main method.

Output

12 is a composite number.

Compile and run the program to see whether the input number is a composite number.

🧠 How the Program Works

The program defines a class CompositeNumberChecker containing a static method isComposite that takes a number as input and returns true if the number is composite and false otherwise.
Inside the method, it iterates through numbers from 2 to the square root of the input number.
For each iteration, it checks if the current number is a divisor of the input number.
If it finds a divisor, the number is composite, and the method returns true.
The main method tests the program with a default input value of 12 and displays whether it is a composite number or not.

📏 Between the Given Range

Let's take a look at the Java code that checks for composite numbers in the specified range.

CompositeNumberChecker.java

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public class CompositeNumberChecker {

  // Function to check if a number is composite
  static boolean isComposite(int num) {
    if (num <= 1) {
      return false; // 1 is neither prime nor composite
    }

    for (int i = 2; i < num; i++) {
      if (num % i == 0) {
        return true; // Found a divisor other than 1 and itself
      }
    }

    return false; // No divisors other than 1 and itself
  }

  // Driver program
  public static void main(String[] args) {
    // Check for composite numbers in the range from 1 to 10
    System.out.println("Composite numbers in the range 1 to 10:");

    for (int i = 1; i <= 10; i++) {
      if (isComposite(i)) {
        System.out.print(i + " ");
      }
    }
  }
}

💻 Testing the Program

Output

Composite numbers in the range 1 to 10 are: 
4 6 8 9 10

Run the program to check for composite numbers in the specified range.

🧠 How the Program Works

The program defines a class CompositeNumberChecker containing a static method isComposite that checks if a given number is composite.
The main method iterates through the numbers in the range from 1 to 10 and prints the composite numbers.

🧐 Understanding the Concept of Composite Numbers

Composite numbers are integers greater than 1 that have divisors other than 1 and themselves.

For example, the number 12 is composite because it can be formed by multiplying 2 and 6 or 3 and 4.

🎢 Optimizing the Program

While the provided program is effective, consider exploring and implementing optimizations for larger numbers, such as checking divisors up to the square root of the number for improved efficiency.

Feel free to incorporate and modify this code as needed for your specific use case. Happy coding!