732: Remove trailing whitespace

[dsgrieve]

What's changed?

Recipe to remove trailing whitespace

What's your motivation?

Fixes #732

Anything in particular you'd like reviewers to focus on?

Anyone you would like to review specifically?

Have you considered any alternatives or workarounds?

Any additional context

Patterned after other RemoveTrailingWhitespace recipes in openrewrite/rewrite.

Checklist

• I've added unit tests to cover both positive and negative cases
• I've read and applied the recipe conventions and best practices
• I've used the IntelliJ IDEA auto-formatter on affected files

[Jenson3210]

Suggested change

	input.append("Line ").append(i);
	expected.append("Line ").append(i);
	// Add i spaces as trailing whitespace
	for (int j = 0; j < i; j++) {
	input.append(" ");
	}
	input.append("Line ").append(i).repeat(" ", i);
	expected.append("Line ").append(i);

Java 21 has this new repeat method on StringBuilder

[dsgrieve]

Added in Java 11, IIRC.

[Jenson3210]

I meant: the tests run in Java 21, so this could be used here, no?

[Jenson3210]

A PlainTextVisitor does not act on Java files. If you would want to "downcast" the Java lst as a text lst, you could build a generic TreeVisitor that does that conversion.

In this case though you do not want to do that as you will loose all rich information of the lst and every recipe that should run on java files after this one will not make any changes as the Lst's at that moment are no longer JavaSourceFiles but PlainText Sourcefiles causing the isAcceptable of the JavaVisitor to skip the converted files.

[Jenson3210]

see https://moderneinc.slack.com/archives/C088P8067NH/p1757442137104209