import java.util.*;
import java.util.regex.*;
 
class rTest {
  public static void main (String[] args) {
 
 
String s = "This is a test [url] http://w...content-available-to-author-only...m.hk [/url]\n"
         + " and [img] http://w...content-available-to-author-only...c.com/test.png [/img]";
 
Pattern p = Pattern.compile("\\[[^\\]]*\\]([^\\]]*)\\[[^\\]]*\\]");
Matcher m = p.matcher(s);
while (m.find()) {
  System.out.println(m.group(1).trim());
}
 
 
  }
}

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