[JAVA] Regular expressions

Regular expressions

It is used to express a character string pattern in one format. Inconsistencies in the data given in the forums can be annoying and are used to eliminate those parts.

In short, error checking

Regular expressions.txt

Postal code[678-0041]    [Search]
          [678]-[0041]  [Search]

Regular expression notation

[0-9]{3} - [0-9]{4}
Enter the numbers 0-9 three times
Add a hyphen
Enter the numbers 0-9 four times
Error if not included

The notational feeling of the rules.

When writing in JAVA.


class Test{
   public static void main(String[] args){

      String strZip = request.getParameter("zip");
      String zipPattern = "[0-9]{3}-[0-9]{4}";

      //This is important Apply the above rules.
      Pattern p = Pattern.compile(zipPattern);

      if (p.matcher.(strZip).find()) { //find()so[true/false]Is passed as the return value.
         //Zip code format
      } else {
         //Input format is error


Regular expressions

By using javascript, it is also possible to run a warning when the focus is out.

symbol Explanation of symbols
Any one character. Omit the newline character
Matches 0 or more repetitions of the previous character
The beginning of the line ^ (hat character)
End of line
[ ] Match any single character in parentheses,-Range can be specified with
{ } Describe the number of repetitions of the numerical value in parentheses.
Repeat the previous expression 0 or 1 times

Regular expression example sentences

Phone number: ^ [0-9] {2,4}-[0-9] {2,4}-[0-9] {3,4} $ Specify the range of {} separated by commas

^ [\ w] + $: \ w Half-width alphanumeric characters ^ \ d {3} \-\ d {4} $: \ d Post office number

The symbol is described by \ w \ d.

Regarding escape statements.

Describe with a yen mark (backslash). I think \ n is basically good.

Output on the console.

① My name is Yamada. System.out.println ("My name is Yamada.");

② My name is "Yamada". System.out.println ("My name is " Yamada \ ".");


  1. a-z ↩︎

  2. A-Z ↩︎

  3. a-zA-Z ↩︎

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