Java Program to find Number Combination

Posted in Java Tutorial

Updated on Oct 30, 2024

By Mari Selvan

👁️ 86 - Views

⏳ 4 mins

💬 1 Comment

Photo Credit to CodeToFun

🙋 Introduction

In the realm of programming, creating combinations of numbers is a common and useful task. A combination is a selection of items from a collection, where the order of selection does not matter.

In this tutorial, we'll explore a Java program that generates combinations of two specified numbers within a given range.

📄 Example

Let's take a look at the Java code that achieves this functionality.

NumberCombinations.java

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public class NumberCombinations {

  // Function to calculate the number of digits in a number
  static int countDigits(int num) {
    int count = 0;
    while (num != 0) {
      num /= 10;
      ++count;
    }
    return count;
  }

  // Function to generate combinations of two numbers up to a specified limit
  static void generateCombinations(int number1, int number2, int limit) {
    System.out.printf("List of combinations of %d and %d up to %d:%n", number1, number2, limit);

    for (int i = 1; i <= limit; ++i) {
      int currentNumber = i;

      // Check if the current number contains only the specified digits
      while (currentNumber > 0) {
        int digit = currentNumber % 10;
        if (digit != number1 && digit != number2) {
          break;
        }
        currentNumber /= 10;
      }

      // If the current number contains only the specified digits, print it
      if (currentNumber == 0) {
        System.out.print(i + " ");
      }
    }

    System.out.println();
  }

  // Driver program
  public static void main(String[] args) {
    // Replace these values with your desired numbers and limit
    int targetNumber1 = 4;
    int targetNumber2 = 8;
    int combinationLimit = 500;

    // Call the function to generate combinations
    generateCombinations(targetNumber1, targetNumber2, combinationLimit);
  }
}

💻 Testing the Program

To test the program with different values, replace the values of targetNumber1, targetNumber2, and combinationLimit in the main method.

Output

List of combinations of 4 and 8 up to 500:
4 8 44 48 84 88 444 448 484 488

Compile and run the program to see the list of combinations.

🧠 How the Program Works

The program defines a class NumberCombinations containing static methods to calculate the number of digits and generate combinations of two specified numbers.
Inside the generateCombinations method, it iterates through numbers from 1 to the specified limit.
For each iteration, it checks if the current number contains only the specified digits.
If the condition is met, the current number is a combination, and it is printed.

🧐 Understanding the Concept of Number Combination

Before delving into the code, let's take a moment to understand the concept of combinations. In mathematics, a combination is a selection of items from a collection, where the order of selection does not matter.

For example, consider the specified numbers as 4 and 8. The combinations of 4 and 8 up to 500 include 4, 8, 44, 48, 84, 88, 444, 448, 484, and 488.