Java的变量类型之间可以进行转换，对象之间也可以。
子类对象转为父类对象，可以不进行强制转换，因为子类继承父类对象。
但是，当父类对象转换为子类对象时（当且仅当父类对象本来是由子类默认转换过去的情况），可以对父类对象进行强制转换。
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public class TestObject {
public static void main(String[] args) {
// TODO Auto-generated method stub
Animal a = new Animal();
Dog d = new Dog("yellow");
d.name = "bigYellow";
System.out.println( a.print( d ) );
}
}
class Animal{
String name;
public void setName(String n){
this.name = n;
}
public String getName(){
return this.name;
}
public String print(Animal a){
String result = "";
if (a instanceof Dog) {
Dog d = (Dog)a;
result = "Name:" + a.name + "\n" + "FurColor:" + d.furColor;
}else if (a instanceof Cat) {
Cat c = (Cat)a;
result = "Name:" + a.name + "\n" + "EyeColor:" + c.eyeColor;
}else{
result = "Name:" + a.name;
}
return result;
}
}
class Cat extends Animal{
String eyeColor;
public void setEyeColor(String e){
this.eyeColor = e;
}
public String getEyeColor(){
return this.eyeColor;
}
Cat(String e){
this.setEyeColor(e);
}
}
class Dog extends Animal{
String furColor;
public void setFurColor(String f){
this.furColor = f;
}
public String getFurColor(){
return this.furColor;
}
Dog (String d){
this.setFurColor(d);
}
}
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