多态的作用主要是类型之间的耦合关系，又被称为动态绑定，后期绑定或者运行时绑定；
package com.Polymorphism;
public class Shapes {
public void draw(){
System.out.println("Shapes.draw()");
}
public void erase(){
System.out.println("Shapes.erase()");
}
public void plink(){
System.out.println("Shapes.plink()"+this.getClass());
}
}
package com.Polymorphism;
public class Square extends Shapes {
@Override
public void draw() {
System.out.println("Square.draw()");
}
@Override
public void erase() {
System.out.println("Square.erase()");
}
@Override
public void plink(){
System.out.println("Square.plink()"+this.getClass());
}
}
package com.Polymorphism;
public class Triangle extends Shapes {
@Override
public void draw() {
System.out.println("Triangle.draw()");
}
@Override
public void erase() {
System.out.println("Triangle.erase()");
}
@Override
public void plink(){
System.out.println("Triangle.plink()"+this.getClass());
}
}
package com.Polymorphism;
public class Circle extends Shapes {
@Override
public void draw() {
System.out.println("Circle.draw()");
}
@Override
public void erase() {
System.out.println("Circle.erase()");
}
@Override
public void plink(){
System.out.println("Circle.plink()"+this.getClass());
}
}
package com.Polymorphism;
import java.util.Random;
public class Polymorphism {
private Random random=new Random(47);
public Shapes next(){
switch ((random.nextInt(3))){
default:
case 0:
return new Circle();
case 1:
return new Square();
case 2:
return new Triangle();
}
}
}
package com.Polymorphism;
public class test {
private static Polymorphism polymorphism=new Polymorphism();
public static void main(String args[]){
Shapes[] shapes=new Shapes[12];
for(int i=0;i<shapes.length;i++){
shapes[i]=polymorphism.next();
}
for(Shapes shapes1:shapes){
shapes1.plink();
}
}
}
Triangle.plink()class com.Polymorphism.Triangle
Triangle.plink()class com.Polymorphism.Triangle
Square.plink()class com.Polymorphism.Square
Triangle.plink()class com.Polymorphism.Triangle
Square.plink()class com.Polymorphism.Square
Triangle.plink()class com.Polymorphism.Triangle
Square.plink()class com.Polymorphism.Square
Triangle.plink()class com.Polymorphism.Triangle
Circle.plink()class com.Polymorphism.Circle
Square.plink()class com.Polymorphism.Square
Circle.plink()class com.Polymorphism.Circle
Circle.plink()class com.Polymorphism.Circle
将一个方法调用预期方法体关联起来，称为方法调用；如果在运行前已经被绑定，则称为前期绑定。而对于一个Shapes引用时，无法知道究竟调用那个方法，解决的办法就是后期绑定，也称为运行期绑定或者动态绑定。
注意，在私有方法被”覆盖“,由于私有方法被认为是，private方法，故导出类，无法访问，也就无法被覆盖，只是拥有与基类相同的方法名而已；
静态方法，也不具备多态性；构造器，其实际上也是static方法，也不存在多态性，但是要了解其在多态的复杂情况下的运行情况；
多态情况下的构造器运行为：
1）调用基类构造器，即首先是根基类的构造器，其次是基类的构造器；
2）其次，按照申明顺序调用成员的初始化方法；
3）调用导出类构造器的主体；
举例说明：
package com.Polymorphism;
class Meal{
Meal(){
System.out.println("Meal()");
}
}
class Chese{
Chese(){
System.out.println("Chese()");
}
}
class Lettuce{
Lettuce(){
System.out.println("Lettuce()");
}
}
class Lunch extends Meal{
Lunch(){
System.out.println("Lunch()");
}
}
class dinner extends Lunch{
dinner(){
System.out.println("dinner()");
}
}
public class se extends dinner{
private Chese chese=new Chese();
private Lettuce lettuce=new Lettuce();
public se(){
System.out.println("MEal()");
}
public static void main(String[] args){
new se();
}
}
Meal()
Lunch()
dinner()
Chese()
Lettuce()
MEal()
向上转型，会损失部分导出类的新方法，如果我们要访问这些方法，可以通过向下转型，但是如果类型转换存在错误，会抛出ClassCastException异常；
