Regular expression Automate Validation Regular expression Validation need
- Slides: 10
Regular expression
Automate Validation – Regular expression • Validation need a hard and very complex programming. • Sometimes it looks easy but actually it is not. • So there is a lot of time and efforts waste in this process. • What is the solution? • Regular expression (regex or regexp for short) is a special text string for describing a pattern. • Pattern is an element repeat in a predictable manner.
Cont. • Examples – All telephone numbers have the same form. – All real numbers have the same form. – All the names have the same form – So on. • Two steps to use regular expression: 1. Learn how to write pattern in RE. 2. Passing RE to Library which give you the ability to use it in validity by automata theory.
Simple Patterns • • d or [0 -9] A digit D or [^0 -9] A non-digit s or [ tnx 0 Bfr] A whitespace character S or [^s] A non-whitespace character w or [a-z. A-Z_0 -9] A word character W or [^w] A non-word character. Any character Note: everyone of those pattern represent only one thing one digit one character and so on.
Using Regular Expression in validation • Fortunately java support Regular expression and give us a good library which compile the pattern and make you able to using in validation. • regex = "\d"; • string 1="3"; • System. out. println( string 1+string 1. matches(regex));
Complex pattern As we say simple pattern only one thing Mostly we need more than one thing Ex: number of two digits This called complex which contain one or more simple with reputation • Then we can write our example as dd • What about five digits? One hundred digits • This is illogical to repeat d one hundred time we need new concept. • •
Repetition in Regx • • X? once or not at all X* zero or more times X+ one or more times X{n} exactly n times X{n, } at least n times X{n, m} at least n but not more than m times Where x is pattern Now we can write the previous example by d{100}
Grouping • Regex has two type of grouping – Group mean or (use [] to represent) – Group mean and (use () to represent) • Examples – [abc] mean one character of set {a , b , c} – (abc) mean three characters follow each other – (d[. ])mean digit follow with dot like 1. and 2.
Ranging in Regex • [a-z] one of small characters from a to z • [A-Z] one of capital characters from A to Z • [a-z. A-Z] one of small characters from a to z or one of capital characters from A to Z • [a-ck-z] one of small characters from a to c or one of small characters form k to z (mean one of small characters out characters group between c to k. • [^abc] Any character except a, b, or c • [a-z&&[def]] d, e, or f (intersection)
Cont. • [a-z&&[^bc]] a through z, except for b and c: [ad-z] (subtraction) • [a-z&&[^m-p]] a through z, and not m through p: [a-lq-z](subtraction)
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