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C++ vs Java

There are many differences and similarities between C++ programming language and Java. A list of top differences between C++ and Java are given below:
Comparison Index C++ Java
Platform-independent C++ is platform-dependent. Java is platform-independent.
Mainly used for C++ is mainly used for system programming. Java is mainly used for application programming. It is widely used in window, web-based, enterprise and mobile applications.
Goto C++ supports goto statement. Java doesn't support goto statement.
Multiple inheritance C++ supports multiple inheritance. Java doesn't support multiple inheritance through class. It can be achieved by interfaces in java.
Operator Overloading C++ supports operator overloading. Java doesn't support operator overloading.
Pointers C++ supports pointers. You can write pointer program in C++. Java supports pointer internally. But you can't write the pointer program in java. It means java has restricted pointer support in java.
Compiler and Interpreter C++ uses compiler only. Java uses compiler and interpreter both.
Call by Value and Call by reference C++ supports both call by value and call by reference. Java supports call by value only. There is no call by reference in java.
Structure and Union C++ supports structures and unions. Java doesn't support structures and unions.
Thread Support C++ doesn't have built-in support for threads. It relies on third-party libraries for thread support. Java has built-in thread support.
Documentation comment C++ doesn't support documentation comment. Java supports documentation comment (/** ... */) to create documentation for java source code.
Virtual Keyword C++ supports virtual keyword so that we can decide whether or not override a function. Java has no virtual keyword. We can override all non-static methods by default. In other words, non-static methods are virtual by default.
unsigned right shift >>> C++ doesn't support >>> operator. Java supports unsigned right shift >>> operator that fills zero at the top for the negative numbers. For positive numbers, it works same like >> operator.
Inheritance Tree C++ creates a new inheritance tree always. Java uses single inheritance tree always because all classes are the child of Object class in java. Object class is the root of inheritance tree in java.

what is purpose of jit complier?

It is used to improve the performance.JIT compiles parts of the byte code that have similar functionality at the same time, and hence reduces the amount of time needed for compilation.Here the term ?compiler? refers to a translator from the instruction set of a Java virtual machine (JVM) to the instruction set of a specific CPU.

Object in Java
An entity that has state and behavior is known as an object e.g. chair, bike, marker, pen, table, car etc. It can be physical or logical (tengible and intengible). The example of integible object is banking system.

An object has three characteristics::

1) state: represents data (value) of an object.
2)behavior: represents the behavior (functionality) of an object such as deposit, withdraw etc.
3) identity: Object identity is typically implemented via a unique ID. The value of the ID is not visible to the external user. But,it is used internally by the JVM to identify each object uniquely.

For Example: Pen is an object. Its name is Reynolds, color is white etc. known as its state. It is used to write, so writing is its behavior.
Object is an instance of a class. Class is a template or blueprint from which objects are created. So object is the instance(result) of a class.

Advantage of OOPs over Procedure-oriented programming language
1)OOPs makes development and maintenance easier where as in Procedure-oriented programming language it is not easy to manage if code grows as project size grows.
2)OOPs provides data hiding whereas in Procedure-oriented prgramming language a global data can be accessed from anywhere.
3)OOPs provides ability to simulate real-world event much more effectively. We can provide the solution of real word problem if we are using the Object-Oriented Programming language.

Abstraction
Hiding internal details and showing functionality is known as abstraction. For example: phone call, we don't know the internal processing.

In java, we use abstract class and interface to achieve abstraction.
encapsulation in java oops concepts

Encapsulation
Binding (or wrapping) code and data together into a single unit is known as encapsulation. For example: capsule, it is wrapped with different medicines.

A java class is the example of encapsulation. Java bean is the fully encapsulated class because all the data members are private here.

Object--
Any entity that has state and behavior is known as an object. For example: chair, pen, table, keyboard, bike etc. It can be physical and logical.

Class--
Collection of objects is called class. It is a logical entity.

Inheritance
When one object acquires all the properties and behaviours of parent object i.e. known as inheritance. It provides code reusability. It is used to achieve runtime polymorphism.
polymorphism in java oops concepts

Polymorphism
When one task is performed by different ways i.e. known as polymorphism. For example: to convense the customer differently, to draw something e.g. shape or rectangle etc.

In java, we use method overloading and method overriding to achieve polymorphism.

Another example can be to speak something e.g. cat speaks meaw, dog barks woof etc.

OOPs (Object Oriented Programming System)

java oops concepts Object means a real word entity such as pen, chair, table etc. Object-Oriented Programming is a methodology or paradigm to design a program using classes and objects. It simplifies the software development and maintenance by providing some concepts:

-Object
-Class
-Inheritance
-Polymorphism
-Abstraction
-Encapsulation

Java OOPs Concepts::::
Object Oriented Programming is a paradigm that provides many concepts such as inheritance, data binding, polymorphism etc.

Simula is considered as the first object-oriented programming language. The programming paradigm where everything is represented as an object, is known as truly object-oriented programming language.

Smalltalk is considered as the first truly object-oriented programming language

Operators in java

Operator in java is a symbol that is used to perform operations. There are many types of operators in java such as unary operator, arithmetic operator, relational operator, shift operator, bitwise operator, ternary operator and assignment operator.

Why java uses Unicode System?

Before Unicode, there were many language standards:

->ASCII (American Standard Code for Information Interchange) for the United States.
->ISO 8859-1 for Western European Language.
- >KOI-8 for Russian.
->GB18030 and BIG-5 for chinese, and so on.

This caused two problems::::

1) A particular code value corresponds to different letters in the various language standards.

2)The encodings for languages with large character sets have variable length.Some common characters are encoded as single bytes, other require two or more byte.

To solve these problems, a new language standard was developed i.e. Unicode System.
In unicode, character holds 2 byte, so java also uses 2 byte for characters.
lowest value:\u0000
highest value:\uFFFF