Java introduction:- Java is a class-based, object-oriented programming language that is designed to have as few implementation
dependencies as possible. It is intended to let application developers write once, and run anywhere (WORA), meaning that
compiled Java code can run on all platforms that support Java without the need for recompilation. Java was first released in 1995
and is widely used for developing applications for desktop, web, and mobile devices. Java is known for its simplicity, robustness,
and security features, making it a popular choice for enterprise-level applications.
JAVA was developed by James Gosling at Sun Microsystems Inc in the year 1995 and later acquired by Oracle Corporation. It is a
simple programming language. Java makes writing, compiling, and debugging programming easy. It helps to create reusable code
and modular programs. Java is a class-based, object-oriented programming language and is designed to have as few
implementation dependencies as possible. A general-purpose programming language made for developers to write once run
anywhere that is compiled Java code can run on all platforms that support Java. Java applications are compiled to byte code that
can run on any Java Virtual Machine. The syntax of Java is similar to c/c++.
Implementation of a Java application program involves a following step. They include:
1. Creating the program
2. Compiling the program
3. Running the program• Creating Program
We can create a program using Text Editor (Notepad) or IDE (NetBeans)
class Test
{
public static void main(String []args)
{
System.out.println(“My First Java Program.”);
}
};
File -> Save -> d:\Test.java
• Compiling the program
To compile the program, we must run the Java compiler (javac), with the name of the source file on “command prompt” like as
follows
If everything is OK, the “javac” compiler creates a file called “Test.class” containing byte code of the program.
• Running the program
We need to use the Java Interpreter to run a program.
Primary/Main Features of Java
1. Platform Independent: Compiler converts source code to bytecode and then the JVM executes the bytecode generated by the
compiler. This bytecode can run on any platform be it Windows, Linux, or macOS which means if we compile a program on
Windows, then we can run it on Linux and vice versa.
2. Object-Oriented Programming Language: Organizing the program in the terms of a collection of objects is a way of object-
oriented programming, each of which represents an instance of the class.
The four main concepts of Object-Oriented programming are:
Abstraction
Encapsulation
Inheritance
Polymorphism
3. Simple: Java is one of the simple languages as it does not have complex features like pointers, operator overloading, multiple
inheritances, and Explicit memory allocation.
4. Robust: Java language is robust which means reliable. It is developed in such a way that it puts a lot of effort into checking
errors as early as possible, that is why the java compiler is able to detect even those errors that are not easy to detect by another
programming language. The main features of java that make it robust are garbage collection, Exception Handling, and memory
allocation.
5. Secure: In java, we don’t have pointers, so we cannot access out-of-bound arrays i.e it shows ArrayIndexOutOfBound
Exception if we try to do so.
6. Distributed: We can create distributed applications using the java programming language. Remote Method Invocation and
Enterprise Java Beans are used for creating distributed applications in java. 7. Multithreading: Java supports multithreading. It is
a Java feature that allows concurrent execution of two or more parts of a program for maximum utilization of the CPU.
8. Portable: As we know, java code written on one machine can be run on another machine.
9.Write Once Run Anywhere: As discussed above java application generates a ‘.class’ file that corresponds to our
applications(program) but contains code in binary format.
, Inheritance in Java:- Inheritance in Java is a mechanism in which one object acquires all the properties and behaviors of a parent object. It is an important part
of OOPs (Object Oriented programming system).The idea behind inheritance in Java is that you can create new classes that are built upon existing classes. When
you inherit from an existing class, you can reuse methods and fields of the parent class. Moreover, you can add new methods and fields in your current class
also.Inheritance represents the IS-A relationship which is also known as a parent-child relationship. Terms used in Inheritance
o Class: A class is a group of objects which have common properties. It is a template or blueprint from which objects are created.
o Sub Class/Child Class: Subclass is a class which inherits the other class. It is also called a derived class, extended class, or child class.
o Super Class/Parent Class: Superclass is the class from where a subclass inherits the features. It is also called a base class or a parent class.
o Reusability: As the name specifies, reusability is a mechanism which facilitates you to reuse the fields and methods of the existing class when you create a
new class. You can use the same fields and methods already defined in the previous class.
Syntax:- class Subclass-name extends Superclass-name
{
//methods and fields }
Types of inheritance in java
Single Inheritance Example
When a class inherits another class, it is known as a single inheritance. In the example given below, Dog class inherits the Animal class, so there is the single
inheritance.
class Animal{
void eat(){System.out.println("eating...");}
}
class Dog extends Animal{
void bark(){System.out.println("barking...");} }
class TestInheritance{
public static void main(String args[]){
Dog d=new Dog();
d.bark();
d.eat();
}}
Multilevel Inheritance Example
When there is a chain of inheritance, it is known as multilevel inheritance. As you can see in the example given below, BabyDog class inherits the Dog class which
again inherits the Animal class, so there is a multilevel inheritance.
class Animal{
void eat(){System.out.println("eating...");} }
class Dog extends Animal{
dependencies as possible. It is intended to let application developers write once, and run anywhere (WORA), meaning that
compiled Java code can run on all platforms that support Java without the need for recompilation. Java was first released in 1995
and is widely used for developing applications for desktop, web, and mobile devices. Java is known for its simplicity, robustness,
and security features, making it a popular choice for enterprise-level applications.
JAVA was developed by James Gosling at Sun Microsystems Inc in the year 1995 and later acquired by Oracle Corporation. It is a
simple programming language. Java makes writing, compiling, and debugging programming easy. It helps to create reusable code
and modular programs. Java is a class-based, object-oriented programming language and is designed to have as few
implementation dependencies as possible. A general-purpose programming language made for developers to write once run
anywhere that is compiled Java code can run on all platforms that support Java. Java applications are compiled to byte code that
can run on any Java Virtual Machine. The syntax of Java is similar to c/c++.
Implementation of a Java application program involves a following step. They include:
1. Creating the program
2. Compiling the program
3. Running the program• Creating Program
We can create a program using Text Editor (Notepad) or IDE (NetBeans)
class Test
{
public static void main(String []args)
{
System.out.println(“My First Java Program.”);
}
};
File -> Save -> d:\Test.java
• Compiling the program
To compile the program, we must run the Java compiler (javac), with the name of the source file on “command prompt” like as
follows
If everything is OK, the “javac” compiler creates a file called “Test.class” containing byte code of the program.
• Running the program
We need to use the Java Interpreter to run a program.
Primary/Main Features of Java
1. Platform Independent: Compiler converts source code to bytecode and then the JVM executes the bytecode generated by the
compiler. This bytecode can run on any platform be it Windows, Linux, or macOS which means if we compile a program on
Windows, then we can run it on Linux and vice versa.
2. Object-Oriented Programming Language: Organizing the program in the terms of a collection of objects is a way of object-
oriented programming, each of which represents an instance of the class.
The four main concepts of Object-Oriented programming are:
Abstraction
Encapsulation
Inheritance
Polymorphism
3. Simple: Java is one of the simple languages as it does not have complex features like pointers, operator overloading, multiple
inheritances, and Explicit memory allocation.
4. Robust: Java language is robust which means reliable. It is developed in such a way that it puts a lot of effort into checking
errors as early as possible, that is why the java compiler is able to detect even those errors that are not easy to detect by another
programming language. The main features of java that make it robust are garbage collection, Exception Handling, and memory
allocation.
5. Secure: In java, we don’t have pointers, so we cannot access out-of-bound arrays i.e it shows ArrayIndexOutOfBound
Exception if we try to do so.
6. Distributed: We can create distributed applications using the java programming language. Remote Method Invocation and
Enterprise Java Beans are used for creating distributed applications in java. 7. Multithreading: Java supports multithreading. It is
a Java feature that allows concurrent execution of two or more parts of a program for maximum utilization of the CPU.
8. Portable: As we know, java code written on one machine can be run on another machine.
9.Write Once Run Anywhere: As discussed above java application generates a ‘.class’ file that corresponds to our
applications(program) but contains code in binary format.
, Inheritance in Java:- Inheritance in Java is a mechanism in which one object acquires all the properties and behaviors of a parent object. It is an important part
of OOPs (Object Oriented programming system).The idea behind inheritance in Java is that you can create new classes that are built upon existing classes. When
you inherit from an existing class, you can reuse methods and fields of the parent class. Moreover, you can add new methods and fields in your current class
also.Inheritance represents the IS-A relationship which is also known as a parent-child relationship. Terms used in Inheritance
o Class: A class is a group of objects which have common properties. It is a template or blueprint from which objects are created.
o Sub Class/Child Class: Subclass is a class which inherits the other class. It is also called a derived class, extended class, or child class.
o Super Class/Parent Class: Superclass is the class from where a subclass inherits the features. It is also called a base class or a parent class.
o Reusability: As the name specifies, reusability is a mechanism which facilitates you to reuse the fields and methods of the existing class when you create a
new class. You can use the same fields and methods already defined in the previous class.
Syntax:- class Subclass-name extends Superclass-name
{
//methods and fields }
Types of inheritance in java
Single Inheritance Example
When a class inherits another class, it is known as a single inheritance. In the example given below, Dog class inherits the Animal class, so there is the single
inheritance.
class Animal{
void eat(){System.out.println("eating...");}
}
class Dog extends Animal{
void bark(){System.out.println("barking...");} }
class TestInheritance{
public static void main(String args[]){
Dog d=new Dog();
d.bark();
d.eat();
}}
Multilevel Inheritance Example
When there is a chain of inheritance, it is known as multilevel inheritance. As you can see in the example given below, BabyDog class inherits the Dog class which
again inherits the Animal class, so there is a multilevel inheritance.
class Animal{
void eat(){System.out.println("eating...");} }
class Dog extends Animal{
