Java 8 introduced default methods to evolve the Java Collections Framework, so that it could support the new Streams API without breaking backward compatibility.

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.

Quite often a Java Stream or other component needs an object passed to it in order to perform some type of calculation or process, but when the process is complete, nothing gets returned from the ...