考虑一下:
class A {
int x =5;
}
class B extends A{
int x =6;
}
public class CovariantTest {
public A getObject() {
return new A();
}
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
// TODO code application logic here
CovariantTest c1 = new SubCovariantTest();
System.out.println(c1.getObject().x);
}
}
class SubCovariantTest extends CovariantTest {
public B getObject(){
return new B();
}
}
Run Code Online (Sandbox Code Playgroud)
据我所知,JVM根据其对象的真实类型选择一种方法.这里的真实类型是SubCovariantTest,它定义了一个覆盖方法getObject.
该程序打印5,而不是6.为什么?