Regular Expressions: What are They and Why do They Matter?

When looking at the String.Split function for the programming assignment, I noticed that one of its parameters was “String regex. The description for this method read “Splits this string around matches of the given regular expression”. What I gathered that to mean was that this method could split a string based on a pattern that you gave to the method. But what exactly is a pattern and what is a regular expression?

Regular expressions (called regex sometimes) are actually a huge part of java and other programming languages. Regular expression is an API in java which allows us to define a pattern which can be used to do all sorts of things with text. You can use it to search for a specific pattern, modify text using it, and like I mentioned earlier, you can split a string using one. These patterns can range from just a single character, to complex strings with characters, numbers, and symbols. Its really up to what the programmer wants to use them for. One use for regular expressions it matching. Using these patterns, you can search for instances of the patterns in text and do something as simple as return a Boolean if the pattern is found, or replace every instance of the pattern with something else completely. There are an incredible amount of possible actions you can perform on text using a regular expression. In the tables below there are some already existing patterns but a programmer can design their own pattern if they wish. The Regex is a powerful tool in java and can be incredibly useful to us whenever we deal with text in a program.

Sources:

The quote is from: http://docs.oracle.com/javase/7/docs/api/java/lang/String.html

all the tables are from :http://www.vogella.com/tutorials/JavaRegular Expressions /article          .html#what-are-regular-expressions

other sources used:

http://www.ocpsoft.org/opensource/guide-to-regular-expressions-in-java-part-1/#section-14

http://www.javatpoint.com/java-regex