Using a regular expression to find a repeating pattern in Java

Question

I am working in a regular expresion to match with the following string.

String sample1 = "key:value|key:value|key:value|key:value";

As you can see key:value is periodically repeating and the only separator is the pipe (|).

Considerations :

key => just letters value => letters, + - sings, and numbers (for the moment)

In the order hand , I have the following regex :

    public void testOptionsRules()
{
    String match = "[a-z]+[:][-+]?[a-z_0-9]+";

    boolean option1 = "a:f".matches(match);
    boolean option2 = "ad:d".matches(match);
    boolean option3 = "addc:dd1".matches(match);
    boolean option4 = "min:50".matches(match);
    boolean option5 = "ssss:-10".matches(match);
    boolean option6 = "dropl2etx:5555".matches(match);

    assertTrue(option1 && option2 && option3 && option4 && option5);
    assertFalse(option6);
}

The last test is working great. But How can I match the periodic repetition. I mean key:value|key:value|key:value|key:value.

Thanks

Are you trying to extract the "key:value"'s out of the String? — Solace
– Solace, Commented Mar 9, 2014 at 1:04
@EJP: Why does it have to be minus-plus if it's inside a character class? — aliteralmind
– aliteralmind, Commented Mar 9, 2014 at 4:18

aliteralmind · Accepted Answer · 2014-03-09 01:09:39Z

4

You can use a matcher to cycle through each match in your string:

      import  java.util.regex.Pattern;
      import  java.util.regex.Matcher;
 /**
    <P>{@code java RegexForRepeatingString}</P>
  **/
 public class RegexForRepeatingString  {
    public static final void main(String[] ignored)  {

       String sRegex = "\\b[a-z]+:[+-]?[a-z_0-9]+\\b";

       String sToSearch = "keya:valuea|keyb:valueb|keyc:valuec|keyd:valued";

       Matcher m = Pattern.compile(sRegex).matcher(sToSearch);

       while(m.find())  {
          System.out.println(m.group());
       }
    }
 }

Output:

[C:\java_code\]java RegexForRepeatingString
 keya:valuea
 keyb:valueb
 keyc:valuec
 keyd:valued

answered Mar 9, 2014 at 1:09

aliteralmind

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