Find Strings Containing Only Numbers in an Array

This article explains how to find strings containing only numbers in an array efficiently using Java. When preparing for Java interviews, logical problem-solving skills play a crucial role.

Problem statement:

Write a Java program that identifies strings in an array that consist only of numeric characters (digits 0-9).

Approach to Solve the Problem

We will break the solution into three simple steps:

  1. Use Java’s built-in matches() method with a regular expression \d+. This ensures that the string contains only digits.
  2. Loop through each word in the array and check if it is numeric using the above method.
  3. Store valid numeric strings in a list and print the final result.

Java program to check if a string contains only digits

This Java program identifies strings in an array that consist only of numeric characters (digits).

package com.javacodepoint.stringarray;

import java.util.ArrayList;
import java.util.List;

public class NumericStrings {

	// Method to check if a string contains only numeric characters
	public static boolean isNumeric(String str) {
		return str.matches("\\d+"); // Regular expression to check if the string contains only digits
	}

	// Method to identify numeric strings in an array
	public static List<String> findNumericStrings(String[] words) {
		List<String> numericStrings = new ArrayList<>();

		for (String word : words) {
			if (isNumeric(word)) {
				numericStrings.add(word);
			}
		}

		return numericStrings;
	}

	public static void main(String[] args) {
		// Example array of strings
		String[] words = { "123", "hello", "4567", "world", "8901", "java123" };

		// Find and print numeric strings
		List<String> numericStrings = findNumericStrings(words);
		System.out.println("Numeric strings: " + numericStrings);
	}
}

OUTPUT:
Numeric strings: [123, 4567, 8901]

Conclusion

This approach efficiently filters numeric strings from an array using regex. Understanding such logical problems will strengthen your Java skills for coding interviews.

You can learn the Top 20 string array programs for interview preparation (Click here).

Java logical programs list


Java Basic Programs

Java String Programs

Java String Array Programs

Java Miscellaneous Programs

Java Programs based on the Collection Framework

Leave a Reply

Your email address will not be published. Required fields are marked *