OOP using java (Variable in java) Lecturer: Omeed Mustafa Moham Da Vinci institute of Duhok-Iraq OOP using java

1. OOP - JAVA
Variables in Java
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Department of Computer
PRO – GRADE 5
Lecturer. OMEED M. M

2. Table of contents
 What is Variable?
 Allocating memory
 Types of variables
 Constructor
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3. Variable in Java
Variables used 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
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4. Allocating memory
In order to 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,
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5. Allocating memory
For this purpose 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”
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6. Variable in Java
• Re-difine variable
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7. Variable in Java
• Println
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8. Types of variables
There are Three type of variables:-
1. Instance variables
2. Local variables
3. Class variables (Static variables)
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9. Instance variables
Instance variables Declared 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;
} }
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10. 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.
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11. Class / Static variables
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.
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12. Constructor
A constructor in Java 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
}
}
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13. Types of variables
class A{
int date=50; //_________ variable
static int m=100; //_________ variable
void method(){
int n=90; //________ variable
}
} //end of class
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14. Any Questions ?
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