OOP using java (Variable in java)

OOP using java (Variable in java)

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  OOP - JAVA Variablesin Java 4/6/2022 1 Department of Computer PRO – GRADE 5 Lecturer. OMEED M. M
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  Table of contents What is Variable?  Allocating memory  Types of variables  Constructor 4/6/2022 2
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  Variable in Java Variablesused to store in our computer’s memory Why called it variable? Because the values inside the variables are changeable.  Attributes - things that the object stores data in, generally variables.  Methods - Functions and Procedures attached to an Object and allowing the object to perform actions 4/6/2022 3
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  Allocating memory In orderto store some data in our computer memory we have to allocate some space so how we can do that? we will go through allocating memory, 4/6/2022 4
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  Allocating memory For thispurpose we have to declare variables. How we can declare variable we are going to using assignment We can assign a value to a variable by using (Equal =) operator. Ex. String ANY_NAME = “ANY_NAME” 4/6/2022 5
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  Variable in Java •Re-difine variable 4/6/2022 6
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  Variable in Java •Println 4/6/2022 7
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  Types of variables Thereare Three type of variables:- 1. Instance variables 2. Local variables 3. Class variables (Static variables) 4/6/2022 8
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  Instance variables Instance variablesDeclared inside class but not inside method. Ex. Class test{ Int data=15; //instance variable Float pi=3.114f; //instance variable } Cannot be reinitialized directly within class Ex. Class test{ Int data=15; //instance variable data =20; //Error for correction we have to put it into a method void testMethod(){ data=20 // correct; } } 4/6/2022 9
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  Local variables Local variables– Declared inside method or method parameters. Ex. Int areatest (int radius){ Int total = radius * radius; Return total; } -These are not accessible outside method. -They did not get default values. 4/6/2022 10
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  Class / Staticvariables Class variables − are variables declared within a class, outside any method, with the static keyword -Static variable is shared between all objects because it belong to the class. It does not belong to the object -A static variable can be accessed without creating an instance of the class. 4/6/2022 11
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  Constructor A constructor inJava is similar to a method that is invoked when an object of the class is created. Unlike Java methods, a constructor has the same name as that of the class and does not have any return type. For example, class Test { Test() { // constructor body } } 4/6/2022 12
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  Types of variables classA{ int date=50; //_________ variable static int m=100; //_________ variable void method(){ int n=90; //________ variable } } //end of class 4/6/2022 13
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  Any Questions ? 4/6/202214