The super variable is not a reference to a subclass. It is a reference to the superclass.
class MyClass {
void printType() {
System.out.println("This is a MyClass");
}
// MySubClass is a subclass of MyClass. Within this class, the super keyword
// refers to MyClass.
static class MySubClass extends MyClass {
void printType() {
// Tell Java we also want to call the printType method of the super class
super.printType();
System.out.println("This is a MySubClass");
}
}
}
No. Because, what is the guarantee that when the super class code is being executed there will always be a sub class? But, the other way round - sub class object accessing a super class variable is possible because, if a sub class uses inheritance to extend from another class, then it is 100% sure that the parent class is going to be around. So a sub class can access the super class variable.
No. The keyword super is used to refer to the parent class instance while the keyword this is used to refer to the current class instance. You need to learn about Inheritance and Object creation using constructors to learn more about these keywords and their use
The Object class, in the java.lang package, sits at the top of the class hierarchy tree. Every class is a descendant, direct or indirect, of the Object class. Every class you use or write inherits the instance methods of Object. You need not use any of these methods, but, if you choose to do so, you may need to override them with code that is specific to your class
You cannot invoke a constructor explicitly. It will get invoked implicitly when you call the new keyword on the class to create an object of the class. Ex: private ClassExample obj = new ClassExample(); here this new keyword usage on the ClassExample class will invoke the constructor of this class and create an object of that class.
The keyword super is used to refer to the parent class instance of the current class. Lets say we have a class class A extends B { ... public void getName(){ } ... } Lets assume the parent class B also has a method getName() Inside class A if you call getName() it would by default call the current class's method. To make the JVM intentionally call the super class method we can use super if we say super.getName() then the parent class instance of the method would be called.
No. Because, what is the guarantee that when the super class code is being executed there will always be a sub class? But, the other way round - sub class object accessing a super class variable is possible because, if a sub class uses inheritance to extend from another class, then it is 100% sure that the parent class is going to be around. So a sub class can access the super class variable.
object class is a super class for all other class...
No. The keyword super is used to refer to the parent class instance while the keyword this is used to refer to the current class instance. You need to learn about Inheritance and Object creation using constructors to learn more about these keywords and their use
No. The keyword super is used to refer to the parent class instance while the keyword this is used to refer to the current class instance. You need to learn about Inheritance and Object creation using constructors to learn more about these keywords and their use
The super and this keywords are mainly used in case of inheritance. this - refers to the object of the current class instance super - refers to the object of the instance of the parent class of the current class.
"this" represents current instance of a class whereas to access constructor, member variable or method of the super class "super" keyword is used. For ex. public class A { A() {} hello() {}; } public class B { private int x; B() { super(); // call A's constructor } hello(int x) { super.hello(); //calls A's hello() this.x = x; // this.x represents member variable of the class B whereas "x" represents local variable. } }
The Object class, in the java.lang package, sits at the top of the class hierarchy tree. Every class is a descendant, direct or indirect, of the Object class. Every class you use or write inherits the instance methods of Object. You need not use any of these methods, but, if you choose to do so, you may need to override them with code that is specific to your class
Variables of the super class can be accessed using the super keyword. Here is an example. class A { int a; } class B extends A { int a; public B() { super.a = 5; } }
It's part of the language specification that all objects in Java must inherit from Object. Java defines a strict class hierarchy, and enforcing a "super most class" ensures that this ordering is maintained.
Inheritance
You cannot invoke a constructor explicitly. It will get invoked implicitly when you call the new keyword on the class to create an object of the class. Ex: private ClassExample obj = new ClassExample(); here this new keyword usage on the ClassExample class will invoke the constructor of this class and create an object of that class.
The keyword super is used to refer to the parent class instance of the current class. Lets say we have a class class A extends B { ... public void getName(){ } ... } Lets assume the parent class B also has a method getName() Inside class A if you call getName() it would by default call the current class's method. To make the JVM intentionally call the super class method we can use super if we say super.getName() then the parent class instance of the method would be called.