This document discusses variables in Java programming. It explains that variables act like dishes that hold data of a specified type. An example shows declaring an integer variable x and assigning it the value 10, which is correct, while assigning 10 to the variable x would be wrong. It then provides examples of computing areas of shapes like circles and squares using variables to hold values and formulas. The key aspects covered are data types, declaring and assigning values to variables, and using variables in calculations and output.

1. Easy practice with java variables
Java programming
Nooria Esmaelzade
2016

2. Which one keeps the water?? Which one is
preferred??
(A)
(B)
(C)
(D)
Of course this one!!

3. The dish keeps the water or
water keeps the dish???
Of course the dish keeps the
water

4. To keep the data, we need something like a
dish in java
Variables can help us here
They act like the dish
We must define the type of every variable/ dish that holds the data

5. Analyze it, which one is the water and which one is
the dish and which one is the type of the dish??
int x = 10 ;
int 10 = x ;
So is it right or wrong??
Data type
Variable/ dish Data

6. Primitive data types
integral (‫)صحیح‬ floating point(‫)اعشاری‬ Boolean
Byte short int long
8-bit 16-bit 32-bit 64-bit
Float double
32-bit 64-bit
True false

7. Compute the circle area
formula (𝑎𝑟𝑒𝑎 = 𝜋𝑟2)
1- data holders (variables, constant)
2- assign value and calculate the area
3- display the result

8. circle area
public class CircleArea {
public static void main(String[] args) {
// Declare and initialize the variables
double r=10;
final double PI= 3.1415;
// calculate the circle area
double area = PI*r*r;
// display the result
System.out.print("This is the area of circle: "+area +" u263A");
}
}

9. Practice in the class
Get area of a square
Formula( area = 𝑎2
)
public class Squarearea {
public static void main(String[] args) {
//Declare variables
double a;
double area;
// Assign value
a=3;
// get the square area
area=a*a;
// display the result
System.out.println("The area of Square with length " +a+ " is: "+ area);
}
}

10. Assignment
Compute the area of Triangle A =
hbb
𝟐
Compute the rectangle area A= width* length

11. Rectangle area
public class Rectangle {
public static void main(String[] args) {
int l = 20;
int w =10;
int area = l * w;
System.out.println("The area of rectangle is: "+ area);
}
}