Question

I’m taking a beating to build a regular expression.

Rules for matching:

• Must contain the EN string
• The String must be between parentheses
• At the starting parentheses, there must be a !
• The string can be anywhere inside the perentheses
• Should the EN string exist outside parentheses, it mustn’t match

The string to match the RegEx can have the following formats, with the expected respective answers:

public void testRegexToMatchContextToIgnoreFromString() {
    String regex = "\\([^\\(].?[EN+].?\\)";
    assertTrue("!(EN)CLIENT".matches(regex));
    assertTrue("!(EN,PR)CLIENT".matches(regex));
    assertTrue("!(PR,EN)CLIENT".matches(regex));

    assertFalse("!(PR)CLIENT".matches(regex));
    assertFalse("!(CO,PR)CLIENT".matches(regex));
}

I tried various ways, but I understand little on RegEx, so I ended up going in circles not getting anywhere.
Can someone help me?

Answer 1

This should match your requirement (I’ve tested it with you test cases):

String regex = ".*!\\(.*EN.*\\).*";

Explanation: First zero or more of any character (.*). Then ‘!(‘, then zero or more of any character, then ‘EN’, then zero or more of any character, then the closing parenthesis and again zero or more of any character.