I have an input string of the following format:
Message:id1:[label1:label2....:labelN]:id2:[label1:label2....:labelM]:id3:[label1:label2....:labelK]...
It is basically ids associated with sets of labels. There can be an arbitrary number of ids and labels associated with those ids.
I want to be able to parse this string and generate a HashMap of the form id->labels for quick look up later.
I was wondering what would be the most efficient way of parsing this message in java?
Something like this should work for you:
String str = "Message:id1:[label1:label2:labelN]:id2:[label1:label2:labelM]:id3:[label1:label2:labelK]";
Pattern p = Pattern.compile("([^:]+):\\[([^\\]]+)\\]");
Matcher m = p.matcher(str.substring(8));
Map<String, List<String>> idmap = new HashMap<String, List<String>>();
while (m.find()) {
List<String> l = new ArrayList<String>();
String[] tok = m.group(2).split(":");
for (String t: tok)
l.add(t);
idmap.put(m.group(1), l);
}
System.out.printf("IdMap %s%n", idmap);
Consider using Guava's Multimap
If you take the string you gave:
Message:id1:[label1:label2....:labelN]:id2:[label1:label2....:labelM]:id3:[label1:label2....:labelK]
And do String.split("]"), You get:
Message:id1:[label1:label2....:labelN
:id2:[label1:label2....:labelM
:id3:[label1:label2....:labelK
If you loop through each of those, splitting on [, you get:
Message:id1: label1:label2....:labelN
:id2: label1:label2....:labelM
:id3: label1:label2....:labelK
Then, you can parse the id name out of the first element in the String[], and the labelname out of the second element in the String, and store that in your Multimap.
If you don't want to use Guava, you can also use a Map<String, List<String>>
Following code will serve your requirement.
import java.util.HashMap;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class RegexTest {
public static void main(String[] args){
String msg = "id1:[label1:label2]:id2:[label1:label2:label3]:id3:[label1:label2:label3:label4]";
Pattern pattern = Pattern.compile("id");
HashMap<String,String> kv = new HashMap<String,String>();
Matcher m = pattern.matcher(msg);
int prev = -1;
int next = -1;
int start = -1;
int end = -1;
String subMsg = "";
while (m.find()){
if(prev == -1){
prev = m.end();
}
else
{
next = m.end();
start = prev;
end = next;
subMsg = msg.substring(start,end);
kv.put(String.valueOf(subMsg.charAt(0)),subMsg.substring(subMsg.indexOf("["),subMsg.lastIndexOf("]")+1));
prev = next;
}
}
subMsg = msg.substring(next);
kv.put(String.valueOf(subMsg.charAt(0)),subMsg.substring(subMsg.indexOf("["),subMsg.lastIndexOf("]")+1));
System.out.println(kv);
}
}
Output : {3=[label1:label2:label3:label4], 2=[label1:label2:label3], 1=[label1:label2]}
Live Demo : http://ideone.com/HM7989
String#split()should do the trick.