Java - How can I check for the next upcoming space in a string? (For IRC Bot)

Question

Obviously, for an IRC bot, input is generated by a user typing a single string, usually with a command and a few arguments, each separated by a space. I am coding an IRC bot using Java and would like to parse arguments that might vary in character length and save them into multiple strings for use later. I would like to make a command that looks something like this:

bot.command argument1 argument2 argument3

and I want it to be so that if the message starts with bot.command , then user will store argument1 , time will store argument2 , and date will store argument3 . The thing is, though, that argument1 , argument2 , and argument3 could vary in character length, so doing something like time = message.substring(33, message.length()) will stop reading at the end of the argument, but it won't always read the string where the argument3 's text begins. I need to detect where the separator space is and start reading argument3 from one character after that. And I can't use If statements to determine what the arguments might be, because they could be anything. Here's a template, if the above paragraph isn't clear:

String message //= the IRC message and bot input
String user;
String time;
String date;
if (message.startsWith("bot.command")) {
    user = message.substring(13, detect next space here and stop reading one character before);
    time = message.substring(detect where previous space was and start one character after that, end before next space);
    date = message.substring(detect where previous space was and start one character after that, message.length());
}

I hope that kind of illustrates what I'm trying to do. Thank you for your help!

Answer 1

I'd recommend using String.split, which breaks up a string into an array using a delimiter regular expression. In your case, you might do:

String[] args = message.split("\\s+");
if (args[0].equals("bot.command"))
{
    user = args[1];
    ...
}

The reason I'm splitting on the pattern \\s+ (matches one or more whitespace characters) instead of just a space is that this way the program won't crash if the arguments are separate by more than one space or by something like a tab.

Answer 2

Edit (Removed StringTokenizer example) -

Since StringTokenizer is apparently "legacy", I would use a Scanner like this -

String message = "BOT.command USER_X    THIS_IS_A_TIME THIS_IS_A_DATE";
String user = null;
String time = null;
String date = null;
// Use toLowerCase - assuming it's case insensitive.
if (message.toLowerCase()
    .startsWith("bot.command")) {
  Scanner st = new Scanner(message);
  if (st.hasNext()) {
    st.next();
  }
  if (st.hasNext()) {
    user = st.next();
  }
  if (st.hasNext()) {
    time = st.next();
  }
  if (st.hasNext()) {
    date = st.next();
  }
}
System.out.printf(
    "User = %s,  Time = %s, Date = %s\n", user,
    time, date);

Output is

User = USER_X,  Time = THIS_IS_A_TIME, Date = THIS_IS_A_DATE

Answer 3

If you are taking user input where you are not sure about how many space separated input words will be entered, you can do the following:

String[] terms = message.split("\\s+");
for(String word1 : terms) {
//    doSomething() 
}

But in your case, you just need 3 arguments, hence the looping will be done 3 times in the for loop.