Regex Java

Regular Expressions were added to Java in version 1.4.

In code, a Java regex is a String.

String myRegex = "^[gG]irr?affe";

Strings have a number of backslash escape sequences such as \t (tab) and \b (backspace).

The backslash of a regex escape sequence must be escaped; for example "\b" is a backspace, but "\\b" is a regex word boundary.
The upshot is, if you're testing your regex syntax outside Java (say, using an online regex tester/debugger), you'll need to double the backslashes when you copy it into your Java code.

String wordPattern = "\\b\\w+(?:'(?:[ts]|ll|[rv]e))?\\b";