Collection Framework. Multi-threading in Java. Table of Contents. Save Article. Improve Article. Like Article. Multiply 2 , 4 ;. Multiply 5. Multiply 2 , 7 , 3 ;. Parent a;. Print ;. Recommended Articles. Article Contributed By :. Easy Normal Medium Hard Expert. Writing code in comment? Please use ide. We already have discussed method overriding, where a child class can override a method in its parent. An overridden method is essentially hidden in the parent class, and is not invoked unless the child class uses the super keyword within the overriding method.
Here, we instantiate two Salary objects. One using a Salary reference s , and the other using an Employee reference e. While invoking s. When the compiler sees e. Here, at compile time, the compiler used mailCheck in Employee to validate this statement. This behavior is referred to as virtual method invocation, and these methods are referred to as virtual methods. An overridden method is invoked at run time, no matter what data type the reference is that was used in the source code at compile time.
Overriding is done by using a reference variable of the superclass. Which method to be called is determined based on the object which is being referred to by the reference variable. This is also known as Upcasting.
For example:. In this example, we are creating one superclass Animal and three subclasses, Herbivores, Carnivores and Omnivores. Subclasses extend the superclass and override its eat method. We will call the eat method by the reference variable of Parent class, i. Animal class. As it refers to the base class object and the base class method overrides the superclass method, the base class method is invoked at runtime.
In this example, we are creating one superclass Hillstations and three subclasses Manali, Mussoorie, Gulmarg. Subclasses extend the superclass and override its location and famousfor method.
Hillstations class. We will create two classes Car and Innova, Innova class will extend the car class and will override its run method. In short, a method is overridden, not the data members. Next time when we will call draw , all shapes instances draw method will be called. This Subtype polymorphism generally relies on upcasting and late binding. A casting where you cast up the inheritance hierarchy from subtype to a supertype is termed as upcasting.
In these types of casting no cast, the operator is involved. To call non-final instance methods we use late binding. In short, a compiler should not perform any argument checks, type checks, method calls etc and leave everything on the runtime. Polymorphism in programming is defined usage of a single symbol to represent multiple different types. A polymorphic variable is defined as a variable that can hold values of different types during the course of execution.
Polymorphism in Java makes it possible to write a method that can correctly process lots of different types of functionalities that have the same name. We can also gain consistency in our code by using polymorphism.
Polymorphism has many other characteristics other than Method Overloading and Method Overriding. They include:. Coercion deals with implicitly converting one type of object into a new object of a different kind. This is done automatically to prevent type errors in the code. Programming languages such as C, java etc supports the conversion of value from one data type to another data type.
Data type conversions are of two types, implicit and explicit. Implicit type conversion is automatically done in the program and this type of conversion is also termed coercion.
For example, if an operand is an integer and another one is in float, the compiler implicitly converts the integer into float value to avoid type error. In Operator Overloading, an operator or symbol behaves in more ways than one depending upon the input context or the type of operands. It is a characteristic of static polymorphism.
Operator overloading is the concept of using the operator as per your choice. An operator symbol or method name can be used as a user-defined type as per the requirements. Similarly, operators like!
In both of these cases, the type of argument decides how the operator is interpreted. In Java, the object or instance variables represent the polymorphic variables. This is because any object variables of a class can have an IS-A relationship with their own classes and subclasses. A variable that can hold values of different types during the time of execution is defined as a polymorphic variable.
Parametric polymorphism specifies that while class declaration, a field name can associate with different types and a method name can associate with different parameters and return types. Here, the obj object is a polymorphic variable.
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