why is my string.length 0 if I split this string?

问题:

This question already has an answer here:

• Split string with dot as delimiter 11 answers

This is probably a very easy question but I'm going to give you the code first.

import java.util.Scanner;

public class help {
public static void main(String args[]) {
    Scanner sc = new Scanner(System.in);

    System.out.print("Give: ");
    String s = sc.next();

    String[] parts = s.split(".");

    System.out.println(parts.length);
}
}

Even if I give 192.168.1.1.1.1.1 or 1.2.3 or ... the parts.length will always be 0, can somebody please explain to me why and how I can let it be 4 if i enter 1.2.3.4?

回答1:

You need s.split("\\.") because the argument to split is a regular expression. The . character in a regular expression means "any character", and you need to escape it with the backslash to have it mean "dot".

回答2:

Because "." is a special character, meaning "any character".

You need to escape it to be able to use it as the character ".":

String[] parts = s.split("\\.");