Interface and Inheritance in Java: Inheritance When a class extends another class it. The class that extends is called sub class while the class that is extended is called super class. Technical Articles Understanding Interface-based Programming Understanding Interface-based Programming. Visual Basic does not presently support implementation inheritance, so I will use a Java example to illustrate what implementation inheritance looks. Java interface example : Interfaces are just a definition of behavior. Java Interface is not a class but it is defined in away similar to the class definition. An Interface describes the functions and behaviors of a specific object type but doesn't implement them. Java Abstract class and Interface programming tutorial when to use what by showing interface vs abstract class differences Skip to main content first Technology JAVA Tutorial last Java Abstract Class and Interface. Write A Java Program Using Inheritance And Interface MeaningAny class in java that does not extend any other class implicitly extends Object class. In other words every class in java directly or indirectly inherits Object class. By means of inheritance a class gets all the public, protected properties and methods of the super class no matter which package the sub class is present in. If the sub class is present in the same package as that of super class then it gets the package private properties and methods too. Once the sub class inherits the properties and methods of super class, it can treat them as if it defined them. By using inheritance you can reuse existing code. If you have an already written class (but no source) and it lacks some features then you don. Just extend the class and add a new method that satisfies your needs. Note: Private methods and properties are not inherited. However, if the super class has a private variable and a public method that uses the variable then the variable is made available inside the method in the sub class. You should also note that constructors are never inherited. How to Extend. Use extends keyword to inherit the super class- class A. Multiple inheritance is not supported in Java. Method Overriding And Hiding. Write A Java Program Using Inheritance And Interface SecurityJava Interfaces with example, Multiple inheritance, Marker and tagging interface, Extending interface, fully abstraction and more. I just got through the section on Interfaces (again), but still do not understand how Java Interfaces simulate multiple inheritance. Is there a clearer explanation than what is in the book? Simple Program On Java for the implementation of Multiple inheritance using interfaces to calculate the area of a rectangle and triangle /* Area Of Rectangle and Triangle using Interface. When a sub class defines a method that has same signature and return type (or compatible with return type of super class method) it is called method overriding. Example: class A. So, when we run the above code the method that gets called is print. It() of class B. By overriding print. It() defined in class A, class B can provide a different implementation to it. Still it can access the super class version of the method by using super keyword. Example: class B extends A. But whose print. It() method will be called is not decided during compilation time. Java waits till the runtime of the program and checks which object the reference is pointing to. In this case the object is of class B. This is called dynamic method dispatch or virtual method invocation. Now let. This is a case of method hiding. Example: class A. Here, the reference type is A. So, print. Static() of class A is executed. Casting Objects. Let. We already know that it is possible to create an object of class B and assign it to a reference of type A. But by doing this you will be able to call the methods that are defined in class A only. In order to call the methods that are defined by class B you need to cast the reference. Example: A a=new B(). Specific. To. B(); // illegal. Specific. To. B(); //legal. Constructor Chaining. When we instantiate a sub class the super class constructor also runs. It happens by means of a call to super(). The only condition is that your super class should have a no arg constructor or else it will produce a compile time error. If you have a super class that does not have a no arg constructor then you should call super() with appropriate parameters from your sub class constructor. The concept will be clear from the following example: class A. Every class is a sub class of Object directly or indirectly. A super class reference can refer to a sub class object. If reference is super class and object is of sub class then calling an instance method on it will result in execution of the method defined in sub class. An overridden method has same signature and return type (or compatible with the return type) as that of super class method. We can hide a static method defined in super class by defining a static method having same signature or return type (or compatible with the return type) as that of super class method. When a sub class constructor runs the super class constructor also runs. This is called constructor chaining.
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