Finding a Specific Digit in a Number using Java

By Atul Rai | Last Updated: September 19, 2023 Previous       Next

On this page, we’ll explore a simple yet common problem: finding a specific digit in a given number using Java. We’ll cover both traditional and Java 8 stream-based approaches to solve this problem.

1. Traditional Approach

Let’s start with a traditional approach using loops and basic arithmetic. We’ll write a Java method to find a specific digit within a given number.

package org.websparrow;

public class FindDigit {

    public static void main(String[] args) {
        int givenNumber = 12345678;
        int targetDigit = 5;
        int targetDigit2 = 32;

        if (isNumberAvailable(givenNumber, targetDigit)) {
            System.out.println(targetDigit + " is available in " + givenNumber);
        } else {
            System.out.println(targetDigit + " is not available in " + givenNumber);
        }

        if (isNumberAvailable(givenNumber, targetDigit2)) {
            System.out.println(targetDigit2 + " is available in " + givenNumber);
        } else {
            System.out.println(targetDigit2 + " is not available in " + givenNumber);
        }
    }

    public static boolean isNumberAvailable(int givenNumber, int targetDigit) {
        // Handle negative numbers by converting to positive
        givenNumber = Math.abs(givenNumber);

        // Check if the target digit is zero (special case)
        if (targetDigit == 0 && givenNumber == 0) {
            return true;
        }

        // Iterate through each digit of the given number
        while (givenNumber > 0) {
            int digit = givenNumber % 10; // Extract the last digit
            if (digit == targetDigit) {
                return true; // Found a match
            }
            givenNumber /= 10; // Remove the last digit
        }

        // If the loop finishes without finding a match, return false
        return false;
    }
}

In this approach, we first handle negative numbers by converting them to positive. Then, we use a while loop to extract each digit from the given number and check if it matches the target digit. This loop continues until we’ve checked all the digits. If we find a match, we return true; otherwise, we return false.

Output:

5 is available in 12345678
32 is not available in 12345678

2. Java 8 Stream Approach

Now, let’s explore a more modern and concise way to solve this problem using Java 8 streams:

package org.websparrow.java8;

import java.util.stream.IntStream;

public class FindDigitJava8 {

    public static void main(String[] args) {
        int givenNumber = 12345678;
        int targetDigit = 5;
        int targetDigit2 = 32;

        if (isNumberAvailable(givenNumber, targetDigit)) {
            System.out.println(targetDigit + " is available in " + givenNumber);
        } else {
            System.out.println(targetDigit + " is not available in " + givenNumber);
        }

        if (isNumberAvailable(givenNumber, targetDigit2)) {
            System.out.println(targetDigit2 + " is available in " + givenNumber);
        } else {
            System.out.println(targetDigit2 + " is not available in " + givenNumber);
        }
    }

    public static boolean isNumberAvailable(int givenNumber, int targetDigit) {
        // Handle negative numbers by converting to positive
        givenNumber = Math.abs(givenNumber);

        // Convert the given number to a stream of digits
        IntStream digitStream = String.valueOf(givenNumber).chars().map(Character::getNumericValue);

        // Check if the target digit is in the stream
        return digitStream.anyMatch(digit -> digit == targetDigit);
    }
}

In this Java 8 approach, we use streams to perform the digit search. First, we convert the given number to a string, and then to a stream of characters. We map each character to its numeric value using Character::getNumericValue. Finally, we use anyMatch to check if the target digit is present in the stream.

Related Post: Java 8 Stream API allMatch(), anyMatch() and noneMatch() method Example

Output:

5 is available in 12345678
32 is not available in 12345678

Conclusion

In this blog post, we’ve explored two different approaches to finding a specific digit in a number using Java. The traditional approach provides a detailed, step-by-step solution that works efficiently. On the other hand, the Java 8 stream-based approach offers a more concise and modern solution.

References

1. Exploring the Optional in Java 8
2. Lambda Expressions in Java 8
3. IntStream – JavaDoc