Thread: Need help with regEx

How exactly do regular expressions work in Java? Let's say I have the string:

String test = new String("Sally went to the barn.");
//any string will do this is for experimentation purposes

and I wanted to use the String's split() function... or any regEx function to get all the words out and put them into a neat little ArrayList<String> (or even better a Hashtable<String, Integer> that'll count the amount of times each word appears).

I tried:

String regEx = "\w";
String[] splitter = test.split(regEx);
 
for(int i=0;i<splitter.length;i++){
			System.out.println(splitter[i]);
		}

But the compiler tells me that "\w" is "an invalid escape sequence. How would I go about extracting every word from a string and putting it into a data structure? Please help, I'm so lost.

When you type into the code '\w', it's looking for a single character code which matches that escape character string (which doesn't exist). If you want the Java to use "\w" as a string,you must provide the escape character for the back-slash.

String regEx = "\\w"; // notice the two back-slashes, while in the code it will look like this the string will actually represent "\w" (two characters)
String[] splitter = test.split(regEx);
//... rest of code

instead of "\w" you can just use a space.

 
String[] splitter = test.split(" ");
 
for(int i=0;i<splitter.length;i++){
			System.out.println(splitter[i]);
		}

If you dont want the period in the token just remove the period(s) before you tokenize it.

test=test.replace(".", "");
String[] splitter = test.split(" ");
 
for(int i=0;i<splitter.length;i++){
			System.out.println(splitter[i]);
		}