we will help you to understand about Java OOP’S concepts with examples. oops concepts in java
Extends Java An OOPs language is meant more for reusability. It achieves reusability with "has-a" relation (through composition) and "is-a" relation (through inheritance). For "has-a" relationship, known as composition in Java, refer Composition – "has-a" Relationship. Now let us discuss inheritance and how the reusability is achieved. To get the concept, very small programs are …
Private access specifier and Private variable requires more elaborate discussion as many people are not aware of its in and outs. private variables and methods of a class can be accessed within the same class only. By inheritance, even subclasses cannot use by composition. Maximum extent other classes should call through the public methods of …
Private variable Accessibility Java Private access specifier Read More »
Java novices are not much aware of static vs non-static or static to non-static calling. Let us find the rules through a program. In the following code, show() method is non-static and display() is static. The question is "Can we call a non-static method from static method?". Everyone says simply "no" because it requires an …
What does it mean by Public methods and Private Variables? Declaring methods as public and variables as private is a programming technique and comes with its own advantages. We know private variables or methods cannot be accessed by composition (has-a relationship) by another class where as public members can be accessed. A private variable can …
Can you have Abstract class main() method? Yes, definitely, because main() is a concrete method and abstract class allows concrete methods. But what you can you do with the main() when you are not allowed to create objects of abstract classes. But, you can create objects of another class and use other class methods by …
Java comes with a set of special set of Constructor Properties. List of Constructor Properties What can not? 1. "A constructor cannot be abstract, static, final, native, strictfp, or synchronized". 2. Interface cannot have constructor. 3. Constructor cannot return a value. What can? 1. A constructor can be private. 2. Abstract class can have constructor. …
Access Specifiers Method Overriding: The only rule says: "The subclass overridden method cannot have weaker access than super class method". Let us see the above rule practically in Access Specifiers Method Overriding. class Test { protected void display() // protected specifier { System.out.println(“Hello 1”); } } public class Demo extends Test { void display() // …
We know access specifiers specify the access and access modifiers modify the access of variables, methods and classes. In general, an access modifier works between the classes of the same application or within the classes of same package. Note: I have seen some people calling access modifiers also as specifiers. It seems for them Java …
Java Overload Main Method Summary: It is a frequent asked interview question. Your answer is YES and is explained in simple terms in this tutorial "Java Overload Main Method". Method overloading is nothing but using the same method in the same class a number of times with different parameters. Just like any other method, the …
Declaring a private constructor is a very rare usage. First of all can we do it? Yes, a constructor can be private and a private constructor can be overloaded also. Following program illustrates. public class Test { private Test() { System.out.println(“I am default private constructor”); } private Test(int x) { System.out.println(“I am overloaded private constructor. …
Summary: At the end of this tutorial, you will be comfortable with Multiple Interfaces Implements usage. Looks difficult at the beginning, but put some patience and start reading. Do some small programs to understand still better. This is required for a Developer. Any doubts may be forwarded to me. As Java does not support direct …
Extend Multiple Classes Java Summary: At the end of this tutorial you will understand the usage of Extend Multiple Classes Java in the code. We know earlier that Java does not support multiple inheritance but supports partially through interfaces. After extends there must be only one class of either concrete (non-abstract) or abstract. After implements …
Java does not permit to declare a constructor as static. Following are the reasons. 1. Static means for the same class. For example, static methods cannot be inherited. 2. With static, "this" reference (keyword) cannot be used. "this" is always linked to an object. A constructor always belongs to some object. 3. If a constructor …
Static binding and static polymorphism is achieved through method overloading. Now let us go for dynamic polymorphism. Observe the following code. Program of Java Dynamic Binding Dynamic Polymorphism class Bird { public void eat() // I { System.out.println(“All birds eat”); } } class Peacock extends Bird { public void eat() // II { System.out.println(“Peacock eats …
public static void main is discussed in Simple terms for a very Beginner. In Java, the execution starts from main() method. But for compilation, main() is not required. Java's main() method syntax is quiet different from C/C++. Following is the public static void main complete signature public static void main(String args[]) Every word in the …
Abstract Static Method looks odd as it cannot exist in Java and declaring so, compiler will not keep quiet. Discussed with Example, Screenshot in Simple terms in Question/Answer format for a Beginner. 1. Can we declare Abstract Static Method? Before answering this question, let us brief about abstract methods. Following points are to be remembered …
These are two different concepts which can be explained easily by a novice having a little bit knowledge of abstract classes and interfaces. It is advised to read abstract classes before going through this topics. It gives thorough understanding of abstract classes where some concepts you may not aware of, perhaps. Before going further let …
Abstract class constructor and Interface abstract Read More »
Reference Variables Anonymous objects Summary: By the end of this tutorial "Reference Variables Anonymous objects", you will be comfortable in creation of Java objects, reference variables and anonymous objects. Java includes two types of variables – primitive variables and reference variables. A primitive type refers a primitive data type and reference type refers a class. …
Java Naming Conventions Readability Summary: Unlike C/C++, Java comes with naming conventions to increase the readability of code. This "Java Naming Conventions Readability" explains how to do it. After knowing the rules of identifiers, it is the time to know the another grammar of Java known as "conventions". Conventions increase the readability of the program. …
Java static Variable Method Summary: By the end of this tutorial "Java static Variable Method", you will comfortable to write programs with static variables and methods. After discussing the usage of "this" keyword, let us move to another keyword "static". The "static" keyword is used as an access modifier. Java has access specifiers and access …
