KVCBastardization2.java

package x;

import java.lang.reflect.Method;
import java.util.Collections;
import java.util.List;

public class KVCBastardization {

	public enum Color {
		Red {
			@Override
			public String someInstanceMethod() {
				return "I am red";
			}
		};

		public abstract String someInstanceMethod();

	}

	public static void main( String[] args ) throws Exception {
		System.out.println( Color.class );
		System.out.println( Color.Red.getClass() );
		System.out.println( valueForKey( Color.Red, "someInstanceMethod" ) );
	}

	public static void mains( String[] args ) throws Exception {
		System.out.println( valueForKey( Collections.emptyList(), "size" ) );
		System.out.println( valueForKey( List.of( "Item" ), "size" ) );
	}

	public static Object valueForKey( Object object, String key ) throws Exception {
		return accessibleMethodForKey( object, key ).invoke( object );
	}

	private static Method accessibleMethodForKey( Object object, String key ) throws NoSuchMethodException, SecurityException {
		Class<?> classToUseForLocatingMethod = object.getClass();

		try {
			while( classToUseForLocatingMethod != null ) {
				Method classMethod = classToUseForLocatingMethod.getMethod( key );

				if( classMethod.canAccess( object ) ) {
					// This is the happy path, where we'll immediately end up in 99% of cases
					return classMethod;
				}

				// Here come the dragons...

				// The class doesn't have an accessible method definition. What about the interfaces?
				for( Class<?> interfaceClass : classToUseForLocatingMethod.getInterfaces() ) {
					try {
						final Method interfaceMethod = interfaceClass.getMethod( key );

						if( interfaceMethod.canAccess( object ) ) {
							return interfaceMethod;
						}
					}
					catch( Exception interfaceException ) {
						// Failure to locate methods in interfaces are to be expected. If no interfaces contain the method, we've already failed anyway.
					}
				}

				// Now let's try the whole thing again for the superclass
				classToUseForLocatingMethod = classToUseForLocatingMethod.getSuperclass();
			}
		}
		catch( NoSuchMethodException | SecurityException methodException ) {
			// If the method doesn't exist on the original class we're dead whatever we do regardless of accessibility, so just throw immediately
			throw methodException;
		}

		// FIXME: Don't throw
		return null;
	}
}