When default methods were introduced in Java 8, some developers thought they would be the same as abstract classes. That’s not true, however, because interfaces can’t have state. A default ...

Here’s an example: public abstract class MetalGearCharacter ... to a specific type and use a specific method.” Exception in thread "main" java.lang.ClassCastException ...

protected and private concrete methods, while interfaces have all fields as automatically public, static and final. Interfaces, however, support multiple inheritances where abstract classes don't.