class Demo2_Polymorphic {
public static void main(String[] args) {
/*Father f = new Son(); //父类引用指向子类对象
System.out.println(f.num);
Son s = new Son();
System.out.println(s.num);*/
Father f = new Son();
//f.print();
f.method(); //相当于是Father.method()
}
}
/*
成员变量
编译看左边(父类),运行看左边(父类)
成员方法
编译看左边(父类)，运行看右边(子类)。动态绑定
静态方法
编译看左边(父类)，运行看左边(父类)。
(静态和类相关，算不上重写，所以，访问还是左边的)
只有非静态的成员方法,编译看左边,运行看右边
*/
class Father {
int num = 10;
public void print() {
System.out.println("father");
}
public static void method() {
System.out.println("father static method");
}
}
class Son extends Father {
int num = 20;
public void print() {
System.out.println("son");
}
public static void method() {
System.out.println("son static method");
}
}
1, the characteristics of the multi-state visit of members of the member variables
[1] member variables
-
Compile look to the left (parent), run to the left to see the (parent).
-
Father a = new son ();
Compile look to the left (parent), run to the left to see the (parent).
Father a = new son ();
2, the polymorphic characteristics of the member access member methods
[1] member method
-
Also known as dynamic binding. Compile time will see the parent class there are no print () method. If not then an error
-
Compile look to the left (parent), run to the right to see (subclass).
3, multi-state member access features of the static member methods
[1] static methods
-
Compile look to the left (parent), run to the left to see the (parent).
-
(Static and class-related, not really rewrite, so the visit is to the left of)
-
Only non-static member method, the compiler look left, look to the right to run
-
Static can also be the class name. Method name. transfer. Therefore, in the multi-states. Father F = new Son (). F. method equivalent to the Father. Method name called directly.
class Father {
int num = 10;
public void print() {
System.out.println("father");
}
public static void method() {
System.out.println("father static method");
}
}
class Son extends Father {
int num = 20;
public void print() {
System.out.println("son");
}
public static void method() {
System.out.println("son static method");
}
}