Java 11+ has factory methods for unmodifiable collections: https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/Set.html#unmodifiable https://

Java 11+ has factory methods for unmodifiable collections: https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/Set.html#unmodifiable https://docs.oracle.com/en/java/javase/11/docs/api/java.base...