Java 17 examples: Sealed classes and Pattern Matching for switch

Files created/updated:

• Abc.java — demonstrates sealed types and instanceof pattern matching (no preview needed).
• PatternSwitchExample.java — demonstrates pattern matching for switch (preview in Java 17).

Compile & run

1. Sealed classes example (no preview flags required):

javac Abc.java
java Abc

2. Pattern matching for switch (preview feature in Java 17): compile and run with preview enabled:

javac --enable-preview --release 17 PatternSwitchExample.java
java --enable-preview PatternSwitchExample

Notes:

• PatternSwitchExample uses a preview language feature in Java 17; the --enable-preview flag is required at both compile and run time.
• If your javac/java targets a newer JVM, adjust the --release/--source flags accordingly.