What's changed?

Switches are not changed to switch expressions when it leads to uncompilable code.

What's your motivation?

When running the recipes on a Java 17 codebase, certain transformations could result in uncompilable code.
For example, applying the SwitchCaseAssignmentsToSwitchExpression recipe to:

String formatted = "initialValue";
switch (str) {
    case "foo": formatted = "Foo"; break;
    case "ignored", default: formatted = "unknown";
}

would produce:

String formatted = switch (str) {
    case "foo" -> "Foo";
    case "ignored", default -> "unknown";
};

While the original statement compiles under Java 17, the transformed switch expression triggers the following error:

patterns in switch statements are a preview feature and are disabled by default.

This happens because combining a constant label (e.g., "ignored") with default in a single case label is only permitted with the pattern matching for switch preview feature in Java 17, which was finalized in Java 21.

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