检查String是否是特定形式的JAVA

Question

Lets say I have a string

String line = "Let x0 be {1,2,3,4}"

How can I check if it the String is written in "Let ??? be ???"

I was trying with the code below but I thing you need to know the length of the ??? to make it work

 matches = line.matches("Let \\d be \\d")

Thank you

Answer 1

\\d only match digit, short for [0-9], it can't match x0 , neither any char of "{,}" so you can match with \\S , which means a non-whitespace character. and since you do not know the length, and expect at least one, can add " + " to \\S, like \\S+ . so this one can match your expect: Let \\S+ be .*

Answer 2

try this regex "Let (\\w+) be (\\S+)"

String line = "Let x0 be {1,2,3,4}";
Pattern p = Pattern.compile("Let (\w+) be (\S+)");
Matcher m = p.matcher(line);
int lastMatchPos = 0;
while (m.find()) {
   System.out.println(m.group(1));
   System.out.println(m.group(2));
   if(m.group(2).length> m.group(1).length){
        //do something you want
   }
}