逗号之间的正则表达式单词

Question

I have the following types of sentences to filter:

Citizens of Poland, Sweden, United States require something

Citizens of Poland require something

Citizens of United States require something

I want to separate names of countries and later save them. I've built the following regex mechanism for that.

String sentence;
[...]
Pattern pattern  = Pattern.compile("(?:Citizens of )? ([A-Z][a-z]+\\s*[A-Z]*[a-z]*) require");
Matcher matcher = pattern.matcher(sentence);
while (matcher.find())
        System.out.println(matcher.group(1));

It works perfect for 2 of 3 cases;

1. Citizens of Poland require something
2. Citizens of United States require something

How can I build a regex pattern to get words if there's more than one?

Answer 1

You may try this regex in Jave with \G and a lookahead:

(?:^Citizens of|(?!^)\G,) ([A-Z][a-z]+(?: [A-Z][a-z]+)*)(?=[a-zA-Z, ]*? require something$)

RegEx Demo

RegEx Details:

• (?: Start non-capture group
  • ^Citizens of Match text Citizens of at the start
  • | OR
  • (?,^)\G, \G asserts position at the end of the previous match or the start of the string for the first match. We match a comma after the previous match of a country name
• ) End non-capture group
• Match a space
• ( Start capture group
• [AZ][az]+ Match an uppercase word
• (?: Start non-capture group
  • [AZ][az]+ Match space followed by a word whose first letter is in uppercase
• )* End non-capture group. * means match 0 or more of this group
• ) End non-capture group
• (?= Start lookahead condition
  • [a-zA-Z, ]*? require something$ [a-zA-Z, ]*? require something$ Assert that we have 0 or more alphabets, comma or spaces before matching text require something
• ) End lookahead