An example of JDK 8 default methods.

Person.java

public interface Person {

  public abstract String getFirstName();
  public abstract String getLastName();

  public default String getDisplayableFullName() {
    return getLastName() + ", " + getFirstName();
  }

  public abstract boolean isStudent();

  public default boolean isNotStudent() {
    return !isStudent();
  }

}