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Java Abstraction step by step example

Abstraction refers to the ability to make a class abstract in OOP. An abstract class is one that cannot be instantiated. All other functionality of the class still exists, and its fields, methods, and constructors are all accessed in the same manner. You just cannot create an instance of the abstract class. If a class is abstract and cannot be instantiated, the class does not have much use unless it is subclassed. This is typically how abstract classes come about during the design phase. A parent class contains the common functionality of a collection of child classes, but the parent class itself is too abstract to be used on its own. Abstract Class: Use the abstract keyword to declare a class abstract. The keyword appears in the class declaration somewhere before the class keyword. /* File name : Employee.java */ public abstract class Employee { private String name ; private String address ; private int number ; public Employee ( String name...
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Java Packages step by step solution with example ( what is Packages in java )

Packages are used in Java in-order to prevent naming conflicts, to control access, to make searching/locating and usage of classes, interfaces, enumerations and annotations easier etc. A Package can be defined as a grouping of related types(classes, interfaces, enumerations and annotations ) providing access protection and name space management. Some of the existing packages in Java are:: java.lang - bundles the fundamental classes java.io - classes for input , output functions are bundled in this package Programmers can define their own packages to bundle group of classes/interfaces etc. It is a good practice to group related classes implemented by you so that a programmers can easily determine that the classes, interfaces, enumerations, annotations are related. Since the package creates a new namespace there won't be any name conflicts with names in other packages. Using packages, it is easier to provide access control and it is also easier to locate the rela...
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What is Java Serialization and what is used of Serialization in java and how to De-serializingan

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Java Serialization Mechanism:   Java provides a mechanism, called object serialization where an object can be represented as a sequence of bytes that includes the object's data as well as information about the object's type and the types of data stored in the object. After a serialized object has been written into a file, it can be read from the file and deserialized that is, the type information and bytes that represent the object and its data can be used to recreate the object in memory. Most impressive is that the entire process is JVM independent, meaning an object can be serialized on one platform and deserialized on an entirely different platform. Classes ObjectInputStream and ObjectOutputStream are high-level streams that contain the methods for serializing and deserializing an object. The ObjectOutputStream class contains many write methods for writing various data types, but one method in particular stands out: public final void writeObject ( Obje...
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