REGEX - It's a Piece of Cake!

Hello everyone!!💝

Are you confused with the title😅? Do you also stay away from regular expressions? Do you use google while solving regex problems? Not after reading this article!😋

C'mon, let's learn it together.🤗

Why Regular Expressions?
Cheatsheets
How to write Regular Expressions?

Why Regular Expressions?

Regex(Regular Expressions) is used to define various types of string patterns which can be used for manipulating, searching, or editing a string. It can be used in all types of text search and text replace operations. Simply, a regular expression is a sequence of characters that helps us to match or find strings.

As we are now aware of regex, let's see how to write it.🤩

Cheatsheets

Matching Symbols

Note: [^regex] and ^regex are totally different.

Meta Characters

Quantifiers

How to write regular expressions?

We should write a regular expression pattern in such a way that it satisfies the required output. Many of them feel regex is hard because of this. So, let's solve some examples to understand this more clearly.

disclaimer: I am using java methods in solutions below. If you are willing to use other languages just check with the regular expression, which is our main goal.😉

Question-1: Given string is "I love Hashnode. It is a wonderful platform." Write a matching regular expression that split the string into tokens.
```
String s="I love Hashnode. It is a wonderful platform." ;  
s=s.replaceAll("[^\\w]", " ");
```
As we take only words as tokens we have to remove . after each sentence. So, we used [^\\w] in replaceAll() to replace all characters except [a-zA-Z_0-9] with a white-space. Now, to split them into tokens we do👇
```
String[] str=s.split("[\\s]+");
```
Here, we are scanning for a token until a white-space occurs. We identified white spaces using [\\s]. Since there can be a sequence of more than one white spaces we also used a +.

Output: [I, love, Hashnode, It, is, a, wonderful, platform]

Question-2: Given a string "I l1ove Hashn7ode. It is 3a wond5erful pla4tform.". Our aim is to print only numbers from this string.
```
String s="I l1ove Hashn7ode. It is 3a wond5erful pla4tform.";  
s=s.replaceAll("[^0-9]", " ");
```
Our aim is to get numbers right? So, I am replacing everything with a white-space expect 0-9 using [^0-9].
```
s=s.trim();
String[] str=s.split("[\\s]+");
```
- Why we used trim()?

trim() is used to remove trailing and leading spaces. After replacing alphabets with a white-space, we get trailing spaces because of I in " I love Hashnode". Since trailing spaces cannot be identified with [\\s]+ we used trim().

Output:  [1, 7, 3, 5, 4]

That's all people😍. Now, we can write any regex patterns in any language by using these cheat sheets.

Say bye-bye to google!😁

REGEX - It's a Piece of Cake!

CONTENTS

Why Regular Expressions?

Cheatsheets

How to write regular expressions?

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