search
HomeJavaJavagetting StartedWhat are the differences between abstract classes, ordinary classes and interfaces in Java?
What are the differences between abstract classes, ordinary classes and interfaces in Java?Nov 27, 2019 pm 02:27 PM
javathe differenceabstract classinterface

What are the differences between abstract classes, ordinary classes and interfaces in Java?

Abstract class:

If there is an abstract method in a class, the class becomes an abstract class.

The class in the abstract class must be preceded by the abstract modifier.

Abstract classes can have ordinary methods or abstract methods, and the number of abstract methods can be 0 or multiple.

The subclass inherits the parent class and must rewrite all abstract methods, unless this class also becomes an abstract class.

Free online learning video recommendation: java online learning

Interface:

On the surface, the interface is a special An abstract class, but a class is a class and an interface is an interface, which is a parallel relationship.

All methods in the interface must be abstract. (Interfaces are allowed to define non-abstract methods after 1.8)

The method definition in the interface defaults to the public abstract type, and the member variables default to the public static final type. (If omitted, the system will complete it by default).

The difference between abstract classes and ordinary classes:

A class that contains abstract methods is called an abstract class, but it does not mean that there can only be abstract methods in abstract classes. Like ordinary classes, they can also have member variables and ordinary member methods.

The difference between abstract classes and ordinary classes is as follows:

The access modifiers of abstract methods must be public and protected.

Abstract classes cannot be instantiated.

If a class inherits from an abstract class, the subclass must implement the abstract method of the parent class. If the subclass does not implement the abstract method of the parent class, the subclass must also be an abstract class.

The difference between abstract classes and interfaces:

A class can only inherit one abstract class, while a class can implement multiple interfaces.

Abstract classes can have constructors, but interfaces cannot have constructors.

There can be member variables in abstract classes, but there are no member variables in interfaces. (Modified by final and turned into a constant)

There can be ordinary methods in abstract classes, but all methods in interfaces must be abstract. (Interfaces are allowed to define non-abstract methods after 1.8)

The access type of abstract methods in abstract classes can be public, protected, but the access type of abstract methods in interfaces It can only be public, and the default is public abstract (if omitted, it will be automatically completed by default).

Member variables in abstract classes can be of various types, while member variables in interfaces can only be of type public static final.

Abstract classes can have static code blocks and static methods, but interfaces cannot contain static code blocks and static methods.

If you want to learn more related articles and tutorials, please visit: Java language introduction

The above is the detailed content of What are the differences between abstract classes, ordinary classes and interfaces in Java?. For more information, please follow other related articles on the PHP Chinese website!

Statement
This article is reproduced at:CSDN. If there is any infringement, please contact admin@php.cn delete
带你搞懂Java结构化数据处理开源库SPL带你搞懂Java结构化数据处理开源库SPLMay 24, 2022 pm 01:34 PM

本篇文章给大家带来了关于java的相关知识,其中主要介绍了关于结构化数据处理开源库SPL的相关问题,下面就一起来看一下java下理想的结构化数据处理类库,希望对大家有帮助。

Java集合框架之PriorityQueue优先级队列Java集合框架之PriorityQueue优先级队列Jun 09, 2022 am 11:47 AM

本篇文章给大家带来了关于java的相关知识,其中主要介绍了关于PriorityQueue优先级队列的相关知识,Java集合框架中提供了PriorityQueue和PriorityBlockingQueue两种类型的优先级队列,PriorityQueue是线程不安全的,PriorityBlockingQueue是线程安全的,下面一起来看一下,希望对大家有帮助。

完全掌握Java锁(图文解析)完全掌握Java锁(图文解析)Jun 14, 2022 am 11:47 AM

本篇文章给大家带来了关于java的相关知识,其中主要介绍了关于java锁的相关问题,包括了独占锁、悲观锁、乐观锁、共享锁等等内容,下面一起来看一下,希望对大家有帮助。

一起聊聊Java多线程之线程安全问题一起聊聊Java多线程之线程安全问题Apr 21, 2022 pm 06:17 PM

本篇文章给大家带来了关于java的相关知识,其中主要介绍了关于多线程的相关问题,包括了线程安装、线程加锁与线程不安全的原因、线程安全的标准类等等内容,希望对大家有帮助。

详细解析Java的this和super关键字详细解析Java的this和super关键字Apr 30, 2022 am 09:00 AM

本篇文章给大家带来了关于Java的相关知识,其中主要介绍了关于关键字中this和super的相关问题,以及他们的一些区别,下面一起来看一下,希望对大家有帮助。

Java基础归纳之枚举Java基础归纳之枚举May 26, 2022 am 11:50 AM

本篇文章给大家带来了关于java的相关知识,其中主要介绍了关于枚举的相关问题,包括了枚举的基本操作、集合类对枚举的支持等等内容,下面一起来看一下,希望对大家有帮助。

java中封装是什么java中封装是什么May 16, 2019 pm 06:08 PM

封装是一种信息隐藏技术,是指一种将抽象性函式接口的实现细节部分包装、隐藏起来的方法;封装可以被认为是一个保护屏障,防止指定类的代码和数据被外部类定义的代码随机访问。封装可以通过关键字private,protected和public实现。

归纳整理JAVA装饰器模式(实例详解)归纳整理JAVA装饰器模式(实例详解)May 05, 2022 pm 06:48 PM

本篇文章给大家带来了关于java的相关知识,其中主要介绍了关于设计模式的相关问题,主要将装饰器模式的相关内容,指在不改变现有对象结构的情况下,动态地给该对象增加一些职责的模式,希望对大家有帮助。

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
2 weeks agoBy尊渡假赌尊渡假赌尊渡假赌
Repo: How To Revive Teammates
1 months agoBy尊渡假赌尊渡假赌尊渡假赌
Hello Kitty Island Adventure: How To Get Giant Seeds
4 weeks agoBy尊渡假赌尊渡假赌尊渡假赌

Hot Tools

Safe Exam Browser

Safe Exam Browser

Safe Exam Browser is a secure browser environment for taking online exams securely. This software turns any computer into a secure workstation. It controls access to any utility and prevents students from using unauthorized resources.

SublimeText3 Linux new version

SublimeText3 Linux new version

SublimeText3 Linux latest version

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)