Java中抽象类和接口之间的区别

先决条件–接口, 抽象类
【Java中抽象类和接口之间的区别】抽象：隐藏功能的内部实现, 仅向用户显示功能。即它的工作原理(显示), 工作原理(隐藏)。都抽象类和接口用于抽象。
抽象类与接口

方法类型：接口只能具有抽象方法。抽象类可以具有抽象和非抽象方法。从Java 8开始, 它还可以具有默认方法和静态方法。
最终变量：在Java接口中声明的变量默认为final。抽象类可能包含非最终变量。
变量类型：抽象类可以具有最终变量, 非最终变量, 静态变量和非静态变量。接口只有静态变量和最终变量。
实现抽象类可以提供接口的实现。接口无法提供抽象类的实现。
继承与抽象：可以使用关键字” implements” 来实现Java接口, 而可以使用关键字” extends” 来扩展抽象类。
多种实现：一个接口只能扩展另一个Java接口, 一个抽象类可以扩展另一个Java类并实现多个Java接口。
数据成员的可访问性：默认情况下, Java接口的成员是公共的。 Java抽象类可以具有类成员, 例如private, protected等。

文章图片

//Java program to illustrate the //concept of abstract classimport java.io.*; //abstract class abstract class Shape { //declare fields String objectName = " " ; Shape(String name) { this .objectName = name; }//declare non-abstract methods //it has default implementation public void moveTo( int x, int y) { System.out.println( this .objectName + " " + "has been moved to" + " x = " + x + " and y = " + y); }//abstract methods which will be //implemented by its subclass(es) abstract public double area(); abstract public void draw(); }class Rectangle extends Shape {int length, width; //constructor Rectangle( int length, int width, String name) {super (name); this .length = length; this .width = width; }@Override public void draw() { System.out.println( "Rectangle has been drawn " ); }@Override public double area() { return ( double )(length*width); } } class Circle extends Shape {double pi = 3.14 ; int radius; //constructor Circle( int radius, String name) {super (name); this .radius = radius; }@Override public void draw() {System.out.println( "Circle has been drawn " ); }@Override public double area() { return ( double )((pi*radius*radius)/2 ); } }class GFG { public static void main (String[] args) {//creating the Object of Rectangle class //and using shape class reference. Shape rect = new Rectangle( 2 , 3 , "Rectangle" ); System.out.println( "Area of rectangle: " + rect.area()); rect.moveTo( 1 , 2 ); System.out.println( " " ); //creating the Objects of circle class Shape circle = new Circle( 2 , "Cicle" ); System.out.println( "Area of circle: " + circle.area()); circle.moveTo( 2 , 4 ); } }

输出如下：

Area of rectangle: 6.0Rectangle has been moved to x = 1 and y = 2 Area of circle: 6.28Cicle has been moved to x = 2 and y = 4

在这种情况下, 矩形和圆形之间没有任何通用代码, 因此可以使用界面。
看到这个……

//Java program to illustrate the //concept of interface import java.io.*; interface Shape { //abstract method void draw(); double area(); }class Rectangle implements Shape { int length, width; //constructor Rectangle( int length, int width) { this .length = length; this .width = width; }@Override public void draw() { System.out.println( "Rectangle has been drawn " ); }@Override public double area() { return ( double )(length*width); } } class Circle implements Shape {double pi = 3.14 ; int radius; //constructor Circle( int radius) {this .radius = radius; }@Override public void draw() { System.out.println( "Circle has been drawn " ); }@Override public double area() {return ( double )((pi*radius*radius)/2 ); }}class GFG { public static void main (String[] args) {//creating the Object of Rectangle class //and using shape interface reference. Shape rect = new Rectangle( 2 , 3 ); System.out.println( "Area of rectangle: " + rect.area()); //creating the Objects of circle class Shape circle = new Circle( 2 ); System.out.println( "Area of circle: " + circle.area()); } }

输出如下