javademos/lanes/src/ReleaseFlag.java

/**
 * Uses one API that exists on Java 26 and later (String.equalsFoldCase) and not on Java 25.
 * Compiled by a newer javac with --release 25 (rejected) and with -source 25 -target 25 (accepted, then it
 * fails when it meets a Java 25 runtime). Explained in docs/15-build-files.md.
 */
public class ReleaseFlag {
    public static void main(String[] args) {
        System.out.println("ABC".equalsFoldCase("abc"));
    }
}