IDE compilation error: Dangling metacharacter

Dangling metacharacter means: the current character calculation has other meanings, and it is not sure what you mean by it.Similar to Chinese polysemy.

As shown in the figure below, when we want to split the "+" in the string, the compilation fails.

Solution:
The first: write "+" as "\+"
The second. Convert "+" into "[+]”;

General metacharacters also include: “.$|()[{^?*+\”.

Of course, regular expressions like "\" and "|" have special meanings. We recommend the second method, otherwise another meaning may appear.
For example:

public class Test {public static void main(String[] args) {String str = "aaa|bbb|ccc|ddd";String[] split = str.split(span>"|");for(String sp: split) {System.out.println(sp);span>}}}

It was found that we compiled successfully, but when I started the main method, the console output:

Indicates when the empty string to split.