Relationship between class and object in oop

Relation between class and object

relationship between class and object in oop

to answer the question let us ask the other what we call an object in the real world it Class and object are two common terms in OOP, but what the different. Our old article based on OOPS show you detail about class and object, now there is a big relationship between class and object. They look very. In object-oriented terminology, a class is a template for defining objects. Many people get confused by the difference between class and object. . In addition to the class hierarchy and composite class relationships, the HLU library has a.

It is assigned to a reference variable that is used to access all of the instance's properties and methods. Think about classes, instances, and instantiation like baking a cake. A class is like a recipe for chocolate cake.

The recipe itself is not a cake. You can't eat the recipe or at least wouldn't want to. If you correctly do what the recipe tells you to do instantiate it then you have an edible cake. That edible cake is an instance of the chocolate cake class.

You can bake as many cakes as you would like using the same chocolate cake recipe. Likewise, you can instantiate as many instances of a class as you would like. Pretend you are baking three cakes for three friends who all have the same birthday but are different ages. You will need some way to keep track of which cake is for which friend so you can put on the correct number of candles.

A simple solution is to write each friend's name on the cake. Reference variables work in a similar fashion. Instance variables and instance methods are non-static variables and methods in a class.

This means that they do not belong to the class itself.

relationship between class and object in oop

Instead, they specify what variables and methods are in an object that belongs to that class. That is, the class contains the source code that defines instance variables and instance methods, but actual instance variables and instance methods are contained in objects.

relationship between class and object in oop

Such objects are called "instances" of the class. Thus, instance variables and instance methods are the data and the behaviors of objects. Explain what is meant by the terms subclass and superclass.

In object oriented programming, one class can inherit all the properties and behaviors from another class. It can then add to and modify what it inherits. The class that inherits is called a subclass, and the class that it inherits from is said to be its superclass. Modify the following class so that the two instance variables are private and there is a getter method and a setter method for each instance variable: To make a variable private, just add the word "private" in front of each declaration.

We need two methods for each variable. One of them returns the value of the variable. The other provides a new value for the variable. The names for these methods should follow the usual naming convention for getter and setter methods.

Note that my setter methods use the special variable this so that I can use the same name for the parameter of the method as is used for the instance variable. This is a very common pattern.

Explain why the class Player that is defined in the previous question has an instance method named toStringeven though no definition of this method appears in the definition of the class.

If a class is not declared to extend any class, then it automatically extends the class Object, which is one of the built-in classes of Java. So in this case, Player is a direct subclass of Object. The Object class defines a toString method, and the Player class inherits this toString method from Object.

The methods and member variables in a class include not just those defined in the class but also those inherited from its superclass. Explain the term polymorphism. Polymorphism refers to the fact that different objects can respond to the same method in different ways, depending on the actual type of the object.

This can occur because a method can be overridden in a subclass.

What is the relationship between Class and Object ?

In that case, objects belonging to the subclass will respond to the method differently from objects belonging to the superclass. If B is a subclass of A, then a variable of type A can refer to either an object of type A or an object of type B. Let's say that var is such a variable and that action is a method in class A that is redefined in class B.

Consider the statement "var.

What is the relation between Classes and Objects | Programming Help

Does this execute the method from class A or the method from class B? The answer is that there is no way to tell!

The answer depends on what type of object var refers to, a class A object or a class B object. For example, the non-instantiable Workstation superclass defines a resource, wkColorMap, that contains a list of currently allocated colors.

In fact, all the resources defined by the Workstation class are available to a PSWorkstation object. Indeed, they are available to objects belonging to any subclass of Workstation, such as the NcgmWorkstation class or the XWorkstation class.

Mixed classes A mixed class is another way to combine the functionality from other classes into a new class. A mixed class manages the properties of other classes and may only use a subset of the functionality of a class, whereas a derived class uses the complete set of functionality of its superclasses and usually extends this functionality.

For example, suppose that in addition to the Box class we have another class called Text. The Text class has one property, called string, with a default value of "hello world. We will call the new class TextBox, and, in this example, it will use all of the properties from both of the classes from which it is composed.

What is the relationship between Class and Object ? - Specialties

In many cases, the mixed class may use only a subset of the properties from these classes. An object that is in the TextBox class would have the following properties: It combines the functionality of the TickMark class and the Title class, among others. Since an XyPlot object contains both tick marks and titles which are both available as HLU classesit is more efficient to have the XyPlot class manage these properties rather than use its own code and properties to provide redundant functionality.

Composite classes In the HLU library, mixed classes are known as "composite classes. For example, if you click on the box PlotManager class, you will see that it has as composite class members the Title, Legend, LabelBar, and TickMark classes.

Composite classes allow access to at least a subset of the resources of their composite class members. Composite class members can be nested. For example, since the ContourPlot class includes the PlotManager as a composite class member, all the composite class members of the PlotManager are available to the ContourPlot class. In other words, you only have to create one object in your HLU program to have the effective functionality of a whole tree of composite class members.

User creatable objects In a user program, only objects belonging to certain classes can be created directly. In the class hierarchy chartthe yellow boxes denote these user-instantiable classes.

The other classes fall into one of four categories: Non-instantiable superclasses such as Base and View Classes designed to function only as composite class members, such as PlotManager and subclasses of the Transformation class The classes that can have only one instance, such as Error and Workspace; they are automatically instantiated when the HLU library is initialized Classes that are instantiated by certain objects for a specialized purpose on behalf of the user; these currently include the XyDataSpec and AnnoManager classes Dynamically associated objects In addition to the class hierarchy and composite class relationships, the HLU library has a mechanism that allows you to associate independently-created View objects dynamically.

You can "overlay" Transform class objects onto a plot object's data space.