java 多态例子

最新推荐文章于 2023-07-21 10:46:40 发布

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最新推荐文章于 2023-07-21 10:46:40 发布

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本文通过示例详细解析了Java中的多态性概念及其实现原理，包括动态绑定与静态绑定的区别，并通过具体代码展示了如何实现方法覆盖与隐藏。

其实也就是两种绑定状态:动态绑定(也称后期绑定),静态绑定(也称前期绑定).

1  实例方法:                                实例方法与引用所实际引用的对象绑定.(动态绑定).
2  静态方法:                                静态方法与引用所实际声明的类型绑定.(静态绑定).
3  成员变量(静态或非静态):         成员变量与引用所实际声明的类型绑定.(静态绑定).

/**
* 多态的演示
* @author fhd001
*/
public class DtTest {
public static void main(String[] args) {
ChildClass c1 = new ChildClass();
c1.aaa();
c1.bbb();
System.out.println(c1.n);
System.out.println(c1.str);
parentClass p1 = new parentClass();
p1.aaa();
p1.bbb();
System.out.println(p1.n);
System.out.println(p1.str);
parentClass p2 = new ChildClass();
p2.aaa(); //aaa()是实例方法,它与实际引用的对象绑定
p2.bbb(); //bbb()是静态方法,它与实际声明的类型绑定
System.out.println(p2.n); //n是变量,它与声明的类型绑定
System.out.println(p2.str); //str变量,它与声明的类型绑定.
}
}
// 父类
class parentClass {
int n = 12;
static String str = "abc";
void aaa(){
System.out.println("parentClass------>aaa");
}
static void bbb(){
System.out.println("parentClass------>bbb");
}
}
//子类
class ChildClass extends parentClass{
int n = 18;
static String str = "efg";
void aaa(){
System.out.println("ChildClass-------->aaa");
}
static void bbb(){
System.out.println("ChildClass-------->bbb");
}
}

例子2：

import java.util.*;

class Shape {
public void draw() {
}

public void erase() {
}
}

class Circle extends Shape {
public void draw() {
System.out.println("Circle.draw()");
}

public void erase() {
System.out.println("Circle.erase()");
}
}

class Square extends Shape {
public void draw() {
System.out.println("Square.draw()");
}

public void erase() {
System.out.println("Square.erase()");
}
}

class Triangle extends Shape {
public void draw() {
System.out.println("Triangle.draw()");
}

public void erase() {
System.out.println("Triangle.erase()");
}
}

class RandomShapeGenerator {
private Random rand = new Random(47);

public Shape next() {
switch (rand.nextInt(3)) {
default:
case 0:
   return new Circle();
case 1:
   return new Square();
case 2:
   return new Triangle();
}
}
}

public class Shapes {
private static RandomShapeGenerator gen = new RandomShapeGenerator();

public static void main(String[] args) {
Shape[] s = new Shape[9];
for (int i = 0; i < s.length; i++)
s[i] = gen.next();
for (Shape shp : s)
shp.draw();
}
}

运行结果为：

Triangle.draw()
Triangle.draw()
Square.draw()
Triangle.draw()
Square.draw()
Triangle.draw()
Square.draw()
Triangle.draw()
Circle.draw()