java_regex

• A Regular Expression is a sequence of characters that constructs a search pattern

• You can use Regex to search for data in a given text.

• Regex is a specific condition for a String and can find it, check if it matches, or manipulate the string to its liking.

• Regex consists of 2 classes, Matcher and Pattern.

• Example of a regex pattern: [a-z0-9]{3,15} -> This example looks for a pattern that contains lowercase letters or digits and length to be between 3 and 15 inclusive

• REGEX Single Character

  • [abc] -> a, b or c
  • [^abc] -> any character except a, b or c
  • [a-zA-Z] -> lowercase or uppercase letter
  • [a-d[m-p]] -> a to d or m to p
  • [a-z[^bc]] -> a to z but not b or c

• REGEX Quantifiers

  • X? -> X occurs once or not
  • X+ -> X occurs more than one time
  • X* -> X occurs zero or more times
  • X{n} -> X occurs n times only
  • X{n,} -> X occurs n or more times
  • X{n, m} -> X occurs at least n times but less than m times

• REGEX Meta Characters

  • . -> represents any character
  • \d -> represents any digit character
  • \D -> represents any non-digit character
  • \s -> represents any white space character
  • \S -> represents any non-white space character
  • \w -> represents any word character a-zA-Z0-9_
  • \W -> represents any non-word character