我正在尝试质疑正则表达式匹配

Question

'[loc]' must be included at the beginning and any character after it does not matter. How do I express it in a regular expression? ex)

>>> [loc]korea
true
>>> [loc] 
false // (One or more strings must follow [loc])
>>> [lll]seoul
false
>>> busan 
false

I used Java and I can't really think of it. Ask for help, brothers

            String pattern = "\\[(loc)\\]"; 
            String val = "[loc]seoul"; 
            String val2 = "[loc]";
            String val3 = "seoul";
        
            boolean regex = Pattern.matches(pattern, val);
            System.out.println(regex);
            boolean regex2 = Pattern.matches(pattern, val2);
            System.out.println(regex2);
            boolean regex3 = Pattern.matches(pattern, val3);
            System.out.println(regex3);

Answer 1

I understand you have some string, a keyword, that must appear at the start of a string. In that case, you need to Pattern.quote to escape any special chars that need escaping and use the .+ pattern to match one or more chars . (You may also consider the .* pattern to match any zero or more chars if your first question sentence is correct and you do not care what is after [loc] .) To also match line breaks, that . does not match by default, you need pass the Pattern.DOTALL option, or prepend your pattern with (?s) inline modifier.

The solution will look like

List<String> vals = Arrays.asList(
    "[loc]seoul", "[loc]", "seoul"
);
String keyword = "[loc]";
String pattern = Pattern.quote(keyword) + ".+";
Pattern p = Pattern.compile(pattern, Pattern.DOTALL);
for (String val : vals) {
    System.out.println(val + ": \"" + p.matcher(val).matches() + "\"");
}

See the Java demo . Output:

[loc]seoul: "true"
[loc]: "false"
seoul: "false"

Answer 2

Its easy. The regex expression should be like loc\w+
For java, you can parse it as loc\\w+

Answer 3

'[loc]' must be included at the beginning and any character after it does not matter. How do I express it in a regular expression? ex)

>>> [loc]korea
true
>>> [loc] 
false // (One or more strings must follow [loc])
>>> [lll]seoul
false
>>> busan 
false

I used Java and I can't really think of it. Ask for help, brothers

            String pattern = "\\[(loc)\\]"; 
            String val = "[loc]seoul"; 
            String val2 = "[loc]";
            String val3 = "seoul";
        
            boolean regex = Pattern.matches(pattern, val);
            System.out.println(regex);
            boolean regex2 = Pattern.matches(pattern, val2);
            System.out.println(regex2);
            boolean regex3 = Pattern.matches(pattern, val3);
            System.out.println(regex3);