Regex - EM JAVA (you did not say the language, I hope it helps!)
Regular expressions (regex), is a resource where we can be doing search with just simple characters (sequence of letters, digits, etc.) or with metacharacters. Therefore, to use such advantages we obviously need to indicate a source and search characters.
Matcher methods: find (), start (), group (), end ();
We have the following font: blue color mouse . So I want to find where the word "color" is in our sentence (in bold). And now!?
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Regex {
public static void main(String[] args) {
String fonte = “mouse da cor azul”;
String queremosIsso = “cor”;
/*
* Nesse momento obteremos uma instância de Pattern, através do * método
* static compile(String regex), o qual recebe uma String que é a
* expressção regular
*/
Pattern p = Pattern.compile(queremosIsso);
/*
* Aqui, através da instancia de Pattern, chamando o método * matcher() e passando a fonte de busca
*/
Matcher m = p.matcher(fonte);
//Ligando o motor
while (m.find()) {
//Obtendo o inicio do que foi encontrado
System.out.println(m.start());
}
}
}
When we execute this code, we will get 9 (nine) as answer. But, why 9?
First let's see what happens.
After we have obtained the Pattern and Matcher instances, in a loop (while) we call the m.find () method. When we call this face, the regex engine is fired, that is, the search task is effectively started. Vale recalls that the regex engine performs the search from left to right and while it encounters an occurrence, it is no longer participating in the search process. Just below the code, I called the m.start () method. This method returns an integer, where it represents the initial index of each sequence found, which in this case would be 9 (nine). I remember starting from scratch. Below is the letters and their indexes (where there are two quotes without content, they represent spaces).
0-m 1-o 2-u 3-s 4-e 5 '' 6-d 7-a 8-
blue color mouse
There is also as I said at the beginning, the group () method. This is responsible for bringing the group of characters that was found in the search.
Ex: // Starting the engine
while (m.find()) {
//Obtendo o inicio do que foi encontrado
System.out.println(m.start() +” “+ m.group() +” “+ m.end());
}
Output: 9 color 12
Then the end () method, where this is the start of start (), bringing the index of the last character found, but this index starts at one (1).
Source: link
