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How do you invoke an overwritten super class from the sub class?
super
How do explicitly invoke overridden superclass method from a subclass?
Use the super keyword. Example: public class Super { public void methodToOverride() { } } public class Sub { @Override public void methodToOverride() { super.methodToOverride(); } }
How is a constructor in the super class called?
By using the reference super(); When you invoke super(); the JVM knows that you are trying to invoke the constructor from the parent class and calls the super class constructor automatically. In fact, the invocation to super(); is usually the first line of any class constructor. This is done to ensure that all the parent class objects are initialized before the current child class is created.
Explain different use of super with the help of java program?
the keyword super is used to access methods/variables of the parent class. ex: public class A { public String getName(){ ..... } } public class B extends A { public String getName(){ ..... } } If you want to access the method getName of class A inside class B you cannot do directly because the compiler would get confused. you need not create an object of A since it is already available. At this point you can use super super.getName() is enough to call the method of the parent class
Tell about static method?
in java a method is said to be static if 'static 'keyword is used before the method name . foe ex.- static void show(){ ........ } this method has the following property-- 1. it can invoke only a static method. 2. it can't be reffered using keyword 'this','super'. 3.static method can access only a STATIC MEMBER VARIABLE or STATIC CLASS VARIABLE . 4. there should not be static & non static version of a nethod in a class . 5.static method can be used before the creation of d object of dt class.
A subclass can call constructor method defined by its super class?
True
Is it possible to have a method in the super class and sub class with same name but different signature?
Yes, it is perfectly possible. If two methods have a different signature, they can exist together irrespective of where they are present, either in the same class or in a super class, sub class situation. If two methods have the same signature and one exists in the super class and one in the sub class it is called method overriding.
Difference between super and final keyword?
this is a reference to the current classsuper is a reference to the super class of the current class (the class from which this class extends). You can use super.super if you want to access the second level class. (The class your parent class extends) The purpose of having thisand super keywords is to differentiate between methods and variables in classes that may have the same name as that in the parent class. Under such situations if we want to ensure that only the methods from a particular class only gets called we can use this and super.
How do explicitly invoke superclass constructor from a subclass?
Using the super keyword. If you call super() from within your constructor, it will explicitly invoke the superclass version of the constructor.
What is function overriding in Java?
Method overriding is similar to method overloading, with a small difference. In overriding, a method in a parent class is overridden in the child class. The method in the child class will have the same signature as that of the parent class. Since the method in the child class has the same signature & name as the method of its parent class, it is termed as overriding. In situations where you may have to explicitly call the parent class method you can use the "super" keyword and for explicitly calling the current objects method you can use the "this" keyword.
How constructor called?
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.
How you compare and contrast overloading and overriding methods in java?
Method overloading is when you have multiple methods in a class that have the same name but a different signature. Method overriding is similar to method overloading, with a small difference. In overriding, a method in a parent class is overridden in the child class. The method in the child class will have the same signature as that of the parent class. Since the method in the child class has the same signature & name as the method of its parent class, it is termed as overriding. In situations where you may have to explicitly call the parent class method you can use the "super" keyword and for explicitly calling the current objects method you can use the "this" keyword.
