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JAVA OOPs Concepts (Object-Oriented Programming System)

It is primarily having below crucial points. Without below essential points, we will never be able to achieve OOPs in java, PHP, C#, etc. Now let us see the high-level understanding of OOPs concepts.

• Object --> is nothing, but it is a real-world entity which we can see or feel. In other words, we can say object have shape, behaviour and from which we can perform some task. For ex: Car, Pen, book, etc. (Object create at runtime and reside in heap memory)
• Class --> in simple words we can say it is a blueprint from which objects can be created. (It contains variables and methods in it) For ex:

                     public class TestCLass1{
                              //This is a java class
                            //It can have variables and techniques and some logics
                      }

• Inheritance--> it is parent-child relationship. A child will acquire all properties from its parent. In other words, child class will acquire all behaviour and properties from the parent class. Importance of keywords in inheritance is (extends, implements). There are 3-4 types of inheritance exist. (IS-a and HAS-a relationship). Do connect with me will explain you in detail followed by real coding on IDEs.
• Polymorphism--> in simple words we can say it is “performing the same task in different ways”. Poly means multiple and morphism means forms in whole (various forms). Two most import topic under this method overloading and method overriding.
• Abstraction-->is data hiding. It is hiding of real implementation and only showing the functionality. For ex: downloading .exe file, it shows only installation not real code behind that .exe file.
• Encapsulation-->Wrapping of data in a single unit. Java class is one of the encapsulation. For ex: just like different medicine wrapped under on capsule is also encapsulation.

               public class TestClass { //Here private sTest is wrapped under TestClass

                        private String sTest="Hi";

                        public String getsTest() {

                              return sTest;}

                        public void setsTest(String sTest) {

                              this.sTest = sTest;

               }}

Please add on comments and like this lesson, if it gave you some revision or refreshment on OOPs concepts.

JAVA - Object Cloning

Is the way of creating the same copy of object without calling the class constructor. It means we can make any class object multiple times without calling its default constructor. Wherever we required the same object then we can go with cloneable classes as loading of the object is pretty much faster as compared to creating new objects multiple times.

Internally it uses clone() method, which is one of the ways of the object class.

We can achieve cloning by implementing any class with the Cloneable interface.

For more understanding please refer below code.

public class EmployeeCloneable implements Cloneable{

          private String name;

          private String add;

          public EmployeeCloneable(String name, String add){ //Only one time constructor cal

                    this.name = name;

                    this.add = add;

                    System.out.println("I am constructor");

          }

          public Object clone() throws CloneNotSupportedException{ 

                    return super.clone(); 

          } 

          public String getName() {

                    return name;

          }

          public void setName(String name) {

                    this.name = name;

          }

          public String getAdd() {

                    return add;

          }

          public void setAdd(String add) {

                    this.add = add;

          }

          public static void main(String[] args) throws CloneNotSupportedException {

                    EmployeeCloneable emp = new EmployeeCloneable("Test", "1");

//try to use comment line then you will be see two time constrictor call happens

                    EmployeeCloneable emp1 = (EmployeeCloneable)emp.clone();//new EmployeeCloneable("Test ", "1");

                    System.out.println(emp);

                    System.out.println(emp1);

          }

          @Override

          public String toString() {

                    return "EmployeeCloneable [name=" + name + ", add=" + add + "]";

          }

}

Output:

I am constructor

EmployeeCloneable [name=Test, add=1]

EmployeeCloneable [name=Test, add=1]

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Spring - Dependency Injection (DI)

DI is a framework which provides loose coupling in code. Here loose coupling means no hard coding of the object. Instead of hard coding, we will be injecting these object from some configurations (XML based, java based, annotation-based).

DI is nothing but design patterns which give you the lightweight loosely couple enterprise application in the result.

What is an injection? -- Inserting of an object/ value into a class whenever the help requires it of third party configurations.

There is two way of achieving Dependency Injection:

• By Constructor
• By Setter method

Constructor Injection: Injecting any object/ value through the constructor of a class. For, e.g., I have a Test class with the parameterized constructor in it, and I am initializing parameter of that constructor from the external source, i.e. XML file. See how

public class Test { 

private int id; 

public Test(int id) {

this.id = id;

} 

}

XML configuration file: //here now 100 will be assigned to the id of Test class

Setter method Injection: Injecting any object/ value through the setter method of a class. For, e.g., I have a Test class with setter method in it, and I am initializing parameter of that setter method from the external source, i.e. XML file. See how

public class Test { 

private int id; 

public int getId() { 

  return id; 

} 

public void setId(int id) { 

   this.id = id; 

}

}

XML configuration file: //here now 100 will be assigned to the id of Test class

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