How to check if a String has digits in Java

In this blog post, I will be explaining how you can check if a String has digits. There are several ways to do this. Consider the following code snippet:

 

package learnjava.strings;import java.util.regex.Pattern;public class CheckIfStringHasDigits {public static void main(String[] args) {String str = "Hello123";String regex = ".*[0-9].*";//Method 1 - Using String.matchesboolean matches = str.matches( regex );System.out.println("Using String.matches="+matches);//Method 2 - Using pattern.matchesmatches = Pattern.matches( regex , str);System.out.println("Using pattern.matches="+matches);//Method 3 - using pattern.compilematches = Pattern.compile( regex).matcher( str ).find();System.out.println("Using Pattern.compile="+matches);//Method 4 - Checking each characterboolean digitFound = false;char[] characters = str.toCharArray();for(char c:characters){if(Character.isDigit(c)){digitFound = true;break;}}System.out.println("Using manual method="+digitFound);}}

 

Method 1

This method uses the String.matches method. This method returns true if the String on which it is invoked matches the regular expression passed.

Method 2:

This method uses the Pattern.matches method. This method accepts a regular expression and String. It returns true if the regular expression matches the input String.

Method 3

This method uses Pattern.compile.matcher.find. This behaves in exactly the same way as Pattern.matches method. However, here the regular expression is compiled separately. If you are using the same regular expression multiple times, compiling it once and using it will give some performance benefits.

Method 4:

This method manually checks each character in the input String. The moment it finds a digit, it returns a true to indicate that there is a digit in the input String.

Comments

Post a Comment

Popular posts from this blog

How to use logging in SpringBoot with code samples

Image
In this article, we will learn how to use logging in SpringBoot. Introduction There are several Java logging frameworks like logback, log4j, and so on. Spring Boot supports out-of-the-box support for logback. Let us learn how to use logging in SpringBoot with logback. Step 1 – Create a New Maven Project Create a new Maven project. (Refer to  this  blog post). This will create a project in Eclipse as follows:   Step 2 – Add the Spring Boot Dependencies Add the spring-boot-starter-web dependency to the pom.xml . So, the pom.xml should look as follows: <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.learnjava</groupId> <artifactId>learnjava-springboot-logging-example</artifactId> <version>0.0.1-SNAPSHOT&
Read more

Python While Loop with code samples

Much like a Java while loop, you can use a Python while loop to repeatedly execute a block of code as long as a condition is true. In this article, we will learn more about the Python while loop. Python While loop Syntax A while loop in Python has the following syntax: while <condition>: loop body The while keyword is followed by a condition. If the condition evaluates to true, the body of the loop is executed. Once the body of the loop is completed, the condition is checked again and this is repeated until the condition evaluates to false at which point the loop is exited. While loop Sample Code The following code demonstrates how you can use the while loop: num=10counter=1total=0while counter<=num: total += counter counter+=1print("sum of first 10 numbers is",total) This code adds the numbers from 1 to 10 and prints the sum. It uses a while loop to iterate from 1 to 10. The while loop checks the condition counter <= num and if so adds the current value of count
Read more

How to convert a List to a Set

In this blog post ,I will be showing you how you can convert a List to a Set. Consider the following code snippet: public class ListToSetDemo {public static void main(String[] args) {List<Integer> list = Arrays.asList(5,3,11,15,9);//Method 1Set<Integer> set = new HashSet<Integer>(list);System.out.println("Set is "+set);//method 2Set<Integer> set2 = new HashSet<Integer>();set2.addAll(list);System.out.println("Set is "+set2);}} This code demonstrates two ways to convert a List to a Set. Method 1 Here, we are creating a new HashSet . We are invoking the constructor that accepts a Collection object. Here, we are passing in the input list to this constructor.   Method 2 Here again, we are creating a new HashSet . However, we are using the default constructor. We are then invoking the addAll method and passing in the input list.   When you run this code, it will print the following output: Set is [3, 5, 9, 11, 15]Set is [3, 5, 9, 11, 15] No
Read more