Duplicate names in molecular class methods

Summary of knowledge points :Java Duplicate names in molecular class methods
4. Duplicate names in molecular class methods
If there are many num, The parent class has a , Subclasses have two , How to print the one you want correctly num Well ？
4.1 Parent class
public class Fu { public int num = 10; }
4.2 Subclass
public class Zi extends Fu {
public int num = 20;
public void methodZi(){
int num = 30;
System.out.println(num); //30, local variable System.out.println(this.num); //20, Member variables of this class
System.out.println(super.num);//10, Member variables of the parent class
} }
4.3 Look at subclass methods methodZi() Can you correctly distinguish three num
public class Demo03Main {
public static void main(String[] args) {
Zi zi = new Zi();
zi.methodZi(); //30, 20, 10
} }
4.4 summary ： To print what you want correctly num, You can do this
local variable , The one above num = 30, You can write directly
Member variables of this class , above num = 20, use this. Member variable name
Member variables of the parent class , above num = 10, use super. Member variable name

5. The problem of duplicate names of member methods in inheritance
   Suppose that both the subclass and the parent class have a method called method() , How do you know which one to use ？

5.1 Parent class
public class Fu {
public void method(){
System.out.println(“ Method execution of parent class with duplicate name ”);
} }
5.2 Subclass
public class Zi extends Fu {
public void method(){
System.out.println(“ Subclass duplicate name method execution ”);
} }
5.3 stay main Call in method() Method
public class Demo04Main {
public static void main(String[] args) {
Fu fu1 = new Fu();
Fu fu2 = new Zi(); // Construct through subclasses fu2
Zi zi = new Zi();
fu1.method(); // Method execution of parent class with duplicate name , The parent method is used
fu2.method(); // Subclass duplicate name method execution , Using subclass methods zi.method(); // Subclass duplicate name method execution , Using subclass methods
} }
Conclusion :
Who is the object created , Whose classes are used to construct objects , Give priority to who , If not, look up .
such as Fu fu2 = new Zi();,fu2 It is constructed with Subclasses , that fu2.method() Is to use the subclass method
Be careful ！ Whether it's a member variable or a member method , If not, look up for the parent class , Never look down for subclasses .