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.

There is a reason why Java method modifiers exist. If you call public methods internally and don't understand why, your developers could face major class issues.