Type Pattern Matching - CORBA Style

package io.github.ikysil.javaplayground.narrow; import java.util.List; import java.util.Optional; public class TypeNarrowDemo { static final class Types { private Types() throws IllegalAccessException { throw new IllegalAccessException(); } static <T> T narrowToNull(final Object obj, final Class<T> expectedType) { if (expectedType.isInstance(obj)) { return expectedType.cast(obj); } return null; } static <T> Optional<T> narrow(final Object obj, final Class<T> expectedType) { return Optional.ofNullable(obj) .map(o -> narrowToNull(o, expectedType)); } } public static void main(String[] args) { System.out.println("TypeNarrowDemo Demo"); if (Types.narrowToNull("test", Object.class) != null) { System.out.println("SUCCESS: String is Object"); } Types.narrow("test", Object.class) .ifPresent(o -> System.out.println("SUCCESS: String is Object: " + o)); if (Types.narrowToNull("test", List.class) == null) { System.out.println("SUCCESS: String is NOT List"); } Types.narrow("test", List.class) .ifPresentOrElse( o -> System.out.println("ERROR: String is NOT List: " + o), () -> System.out.println("SUCCESS: String is NOT List") ); } }