Ever since JDK 8 has allowed concrete methods on interface e.g. default in addition to static methods, many of my readers accept asked me how should they response the classical abstract shape vs interface questions. In this post, I'll revisit this hugely pop Java interview interrogation inward lite of Java 8 changes. Before JDK 8, the marking of abstraction was the clear cutting divergence betwixt abstract shape in addition to interface i.e. interface was the purest shape of abstraction which solely define what interface is supposed to create without specifying how i.e. it solely declare API methods in addition to leave of absence implementation to its subclasses. All methods of an interface were abstract simply since Java 8 y'all tin move define non-abstract methods inward shape of default in addition to static methods within interface inward Java.
This brings many questions come upwards to mind. Prima facia inward Java 8, an interface looks similar an abstract shape in addition to 1 tin move argue about, tin move nosotros utilisation interface alongside default methods inward house of an abstract shape inward Java?
Well, I believe they are for 2 dissimilar purposes in addition to nosotros volition larn to a greater extent than 1 time nosotros starting fourth dimension using Java 8 regularly, simply next semantics divergence betwixt abstract shape in addition to interface alongside default method volition lead y'all farther :
1) Abstract classes are classes, so they are non restricted alongside other restrictions of the interface inward Java e.g. abstract shape tin move accept the state, simply y'all cannot accept the country on the interface inward Java.
2) Another semantic divergence betwixt interface alongside default methods in addition to abstract shape is that y'all can define constructors within an abstract class, simply y'all cannot define constructor within interface inward Java.
In reality, default or defender methods are introduced to hold backward compatibility in addition to same fourth dimension making Collection API to a greater extent than suitable to survive used within fundamental Java 8 features similar lambda expressions. Without adding default methods, it wasn't possible to declare whatever novel method on existing interface inward Java without breaking all classes which implement it, simply because of default method, y'all tin move similar a shot amend evolve your API. They defend your code against implementing novel methods thus they are likewise called defender methods.
Though I sure as shooting concur that divergence betwixt abstract shape in addition to the interface has reduced alongside the introduction of default methods, every bit good every bit allowing static method within interface in addition to their usage volition evolve 1 time Java 8 acquire out a mainstream Java evolution version, simply y'all must think that an abstract shape is a shape in addition to an interface is an interface. If y'all are designing API so utilisation interface in addition to if y'all are abstracting both country in addition to demeanor so utilisation an abstract class.
Further Reading
What's New inward Java 8
Java SE 8 for Really Impatient
From Collections to Streams inward Java 8 Using Lambda Expressions
Streams, Collectors, in addition to Optionals for Data Processing inward Java 8
Related Java 8 Tutorials
If y'all are interested inward learning to a greater extent than almost novel features of Java 8, hither are my before articles roofing some of the of import concepts of Java 8:
Thanks for reading this article so far. If y'all similar this article so delight portion alongside your friends in addition to colleagues. If y'all accept whatever interrogation or feedback so delight driblet a comment.
This brings many questions come upwards to mind. Prima facia inward Java 8, an interface looks similar an abstract shape in addition to 1 tin move argue about, tin move nosotros utilisation interface alongside default methods inward house of an abstract shape inward Java?
Well, I believe they are for 2 dissimilar purposes in addition to nosotros volition larn to a greater extent than 1 time nosotros starting fourth dimension using Java 8 regularly, simply next semantics divergence betwixt abstract shape in addition to interface alongside default method volition lead y'all farther :
1) Abstract classes are classes, so they are non restricted alongside other restrictions of the interface inward Java e.g. abstract shape tin move accept the state, simply y'all cannot accept the country on the interface inward Java.
2) Another semantic divergence betwixt interface alongside default methods in addition to abstract shape is that y'all can define constructors within an abstract class, simply y'all cannot define constructor within interface inward Java.
In reality, default or defender methods are introduced to hold backward compatibility in addition to same fourth dimension making Collection API to a greater extent than suitable to survive used within fundamental Java 8 features similar lambda expressions. Without adding default methods, it wasn't possible to declare whatever novel method on existing interface inward Java without breaking all classes which implement it, simply because of default method, y'all tin move similar a shot amend evolve your API. They defend your code against implementing novel methods thus they are likewise called defender methods.
Though I sure as shooting concur that divergence betwixt abstract shape in addition to the interface has reduced alongside the introduction of default methods, every bit good every bit allowing static method within interface in addition to their usage volition evolve 1 time Java 8 acquire out a mainstream Java evolution version, simply y'all must think that an abstract shape is a shape in addition to an interface is an interface. If y'all are designing API so utilisation interface in addition to if y'all are abstracting both country in addition to demeanor so utilisation an abstract class.
Further Reading
What's New inward Java 8
Java SE 8 for Really Impatient
From Collections to Streams inward Java 8 Using Lambda Expressions
Streams, Collectors, in addition to Optionals for Data Processing inward Java 8
Related Java 8 Tutorials
If y'all are interested inward learning to a greater extent than almost novel features of Java 8, hither are my before articles roofing some of the of import concepts of Java 8:
- 5 Books to Learn Java 8 from Scratch (books)
- How to bring together String inward Java 8 (example)
- How to utilisation filter() method inward Java 8 (tutorial)
- How to format/parse the engagement alongside LocalDateTime inward Java 8? (tutorial)
- How to utilisation Stream shape inward Java 8 (tutorial)
- How to utilisation forEach() method inward Java 8 (example)
- How to convert List to Map inward Java 8 (solution)
- 20 Examples of Date in addition to Time inward Java 8 (tutorial)
- How to utilisation peek() method inward Java 8 (example)
- How to variety the map past times keys inward Java 8? (example)
- How to variety the may past times values inward Java 8? (example)
- 10 examples of Optionals inward Java 8? (example)
- How to convert lambda human face to method reference inward Java 8 (tutorial)
Thanks for reading this article so far. If y'all similar this article so delight portion alongside your friends in addition to colleagues. If y'all accept whatever interrogation or feedback so delight driblet a comment.
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