Regular expressions
A regular expression defines a search pattern for strings. The abbreviation for regular expression is regex. The search pattern can be anything from a simple character, a fixed string or a complex expression containing special characters describing the pattern. The pattern defined by the regex may match one or several times or not at all for a given string.
Regular expressions can be used to search, edit and manipulate text.
Valid IP Address
The basic format of ip addresses format policy is:
- It must start with a number from 0 – 255.
- It must be followed a dot
- This pattern has to repeat for 4 times (eliminating the last dot…)
This is the regex we will use:
"^(([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.){3}" +
"([01]?\\d\\d?|2[0-4]\\d|25[0-5])$"
This will throw the following output:
000.12.12.034 -> valid
121.234.12.12 -> valid
23.45.12.56 -> valid
00.12.123.123123.123 -> invalid
122.23 -> invalid
Hello.IP -> invalid
