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35 Cards in this Set
- Front
- Back
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Objects |
They can hold lots of different datatypes and perform actions using methods |
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Class |
A blue print that defines how the object should look like Lets us design our own objects. |
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Class |
A blue print that defines how the object should look like |
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Static method |
It doesn't need an object to run |
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Object state |
Represents the data of an object |
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Object |
Has all the characteristics of a class |
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Instance variable |
A variable that is created inside of a class but outside of a method.. |
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Instance variable |
Doesn't get memory at compile time.. it gets memory at runtime |
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New Keyword |
Allocates memory at runtime |
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Ways to initialize an object |
By Reference variable
By method
By constructor |
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Anonymous object |
Has no reference.. can be used at the time of object creation.. good for one time object use |
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Constructor |
Similar to a method.. called when an instance of class is created |
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Rules of constructors creation |
Must have the same class name Mus not return any valye Can not be static, abstract, final It can have access modifiers |
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Default constructor |
Created by java when an instance of class is created.. Doesn't have any parameters |
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Default constructor |
Providers default value to objects. Like null or zero or etc.. |
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Constructor overloading |
Having more than one constructor with different parameter lists |
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Static variable |
Used to refer to the common property of all objects like a company name.. it also gets memory only once in the class loading |
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Static method |
Belongs to the class not the object. Can be invoked without the need for creating a class instance. Can access static data member and change its value. |
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Static method restrictions |
Can not use non static data member or call non static method diretly. Can not use this and super keywords. |
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Java static block |
It is executed before the main method at the time of classloading |
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This |
Reference varaible refers to current class |
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Inheritance |
It's a mechanism in which one object inherits the characteristics of another object |
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Why use inheritance |
For method overloading and code reusability |
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Types of inheritance in java |
Single, multi and hierarchical |
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Method overloading |
A class has multiple methods with the same name but different parameters |
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Method Overriding |
If subclass (child class) has the same method as declared in the parent class, it is known as method overriding in Java. |
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Rules of method overriding |
Must have the same name as the method in parent class. Must have same parameter. Must be an IS-A relationship |
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Super |
Prefers to immediate parent class |
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Instance initializer block |
Created when instance of class is created. Invoked after the parent class constructor is invoked(super()) |
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Final class |
A class that can not be extended |
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Final variable |
It can be only initalized once. Its value can not be changed |
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Final method |
Methods that can not be overridden |
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Blank final variable |
A final variable that is not initalized at the time of declaration |
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Polymorphism |
A concept which u can perform single action in different ways |
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Abstraction |
Hiding implementation details and showing only functionality to the user |
