多態：
---一個物件的多種形態
實質：父類別的引用指向子類別物件
---前提：必須有繼承或是實作
class Animal{}
class Dog Dog extends Animal{}
main{
Dog d = new Dog(); //本態
Animal dog = new Dog(); //多態性
}
的對象，只能存取子父類別共有的成員方法，運行結果為子類別結果是子類別特有的成員方法不能方法。 虛擬方法呼叫：父類別物件呼叫子類別特有的方法Student S = new Student("張三",100);Person p = new Student("李四",200);Person p = new Student("李四",200);
System.out.println(S.say());
System.out.println(p.say());
多態性數組— 在引用類型的陣列中，使用多態性形式來存放物件。
eg:Person[] person = {new Person("張三", 32),
new Student("李四", 21, 120, 90.0),
new Student("王五", 22,五", 22, 119, 91.5),
new Teacher("劉老師", 35, 10, "Java EE"),
new Teacher("張老師", 11)};
中的參考型別參數instanceof運算子— 判斷一個物件是否為指定型別（形態）強制型別轉換— 將物件從一種參考型態轉換為另一種參考型態物件關聯：一個物件中使用了另一個物件一對一，一對多，多對一
class test4 {
public static void main(String[] args){
Person p = new Person("王五",50);
method(p);
Student S = new Student("张三",100);
method(S);
Person p1 = new Student("赵四",100);
method(p1);
}
public static void method(Person p){
if (p instanceof Student){
System.out.println("教师");
Student s = (Student)p;
System.out.println("本态方法调用："+p.say());
}else{
System.out.println("人");
}
System.out.println(p.say());
}
}
class Person{
private String name;
private int age;
public Person(){}
public Person(String name,int age){
this.name = name;
this.age = age;
}
public String getName(){
return name;
}
public String say(){
return "姓名:"+name+"年龄:"+age;
}
}
class Student extends Person{
private int id;
private double score;
public Student(String name,int id){
this(name,20,id,98.5);
}
public Student(String name,int age,int id,double score){
super(name,age);
this.id = id;
this.score = score;
}
public double getId(){
return id;
}
public String say(){
return super.say()+"学号:"+id+"分数:"+score;
}
}
