Replacing Blank Lines Using Multiline Mode RegEx Patterns In POSIX And Java In Lucee CFML 5.3.7.47

snippet-1.cfm

<cfsavecontent variable="patternText"
	>(?mx)
	^
	<!---
		By wrapping the "blank line" in a repeating capture group, we use the
		repeating nature of the pattern to replace adjacent lines rather than leaning
		entirely on the "all" behavior of the reReplace() function.
	--->
	(
		[\x20\x09]*
		\n
	)+
</cfsavecontent>

test.cfm

<cfscript>

	// We're building content that multiple "blank lines" next to each other.
	content = arrayToList(
		[
			"AAAAA",
			"BBBBB",
			"",             // Blank line.
			"  ",           // Blank line.
			" #chr( 9 )# ", // Blank line.
			"",             // Blank line.
			"CCCCC",
			"        ",     // Blank line.
			"",             // Blank line.
			"DDDDD"
		],
		chr( 10 )
	);

	// In order to make the Regular Expression (RegEx) pattern easier to read, I am
	// running it in VERBOSE mode (?x). This ignores incidental whitespace and requires
	// all whitespace characters to be explicitly provided. As such, I am using the
	// following HEX codes:
	// --
	// \x20 => Space
	// \x09 => Tab
	// --
	// This Regular Expression pattern is attempting to match "blank lines" (ie, lines
	// that have nothing but whitespace) so that I can strip those lines out in the
	// replacement operation.
	```
	<cfsavecontent variable="patternText"
		>(?mx)       <!--- Multi-Line + Verbose mode enabled. --->
		^            <!--- Match at START OF LINE. --->
		[\x20\x09]*  <!--- Leading Space or Tab characters. --->
		\n           <!--- Match line-break at end of line. --->
	</cfsavecontent>
	```

	// Note that we are using the SAME PATTERN TEXT to apply the changes using the
	// default ColdFusion Regular Expression engine (POSIX) and the lower-level Java
	// Regular Expression engine.
	cfResult = content.reReplace( patternText, "", "all" );
	javaResult = javaCast( "string", content ).replaceAll( patternText, "" );

	echo( "<h3> POSIX (CFML) Result - reReplace() </h3>" );
	echo( "<pre>#encodeForHtml( cfResult )#</pre>" );
	echo( "<h3> Java Result - .replaceAll() </h3>" );
	echo( "<pre>#encodeForHtml( javaResult )#</pre>" );

</cfscript>