Can have private methods with the implementation (introduced in Java 9). Can have any kind of methods. Let’s explore the main differences between interfaces and abstract classes with a Java code ...

In other words, a Java class that supports the SOLID open-closed principle ... you can pass any class that implements the Shape interface as an argument to the OpenClosedExample's compareArea method.

As such, you can incorporate the functional Consumer interface into your code simply by creating a class that implements java.util.function.Consumer, or by coding an inner class. As you can see, there ...