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Java Lecture 2

This document introduces variables and data types in Java. It discusses that variables are used to store and refer to data, and each variable needs a unique name. It then explains the different primitive and non-primitive data types in Java, including their sizes and possible values. Primitive data types include numeric types like int and float, as well as char and boolean. Non-primitive types can be declared using the new keyword and include classes like String and arrays. Finally, the document defines constants as variables that cannot change value once assigned, and provides some homework problems to practice using variables and data types.

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Muhammad Ahmad
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29 views3 pages

Java Lecture 2

This document introduces variables and data types in Java. It discusses that variables are used to store and refer to data, and each variable needs a unique name. It then explains the different primitive and non-primitive data types in Java, including their sizes and possible values. Primitive data types include numeric types like int and float, as well as char and boolean. Non-primitive types can be declared using the new keyword and include classes like String and arrays. Finally, the document defines constants as variables that cannot change value once assigned, and provides some homework problems to practice using variables and data types.

Uploaded by

Muhammad Ahmad
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as DOCX, PDF, TXT or read online on Scribd
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Java - Introduction to Programming

Lab 2

Variables & Data Types

1. Variables
A variable is a container (storage area) used to hold data.
Each variable should be given a unique name (identifier).

Import java.utils.*;

public class Main {

public static void main(String[] args) {


// Variables
String name = "Aman";
int age = 30;

String neighbour = "Akku";


String friend = neighbour;
}
}

2. Data Types
Data types are declarations for variables. This determines the type and size of data
associated with variables which is essential to know since different data types occupy
different sizes of memory.

There are 2 types of Data Types :


- Primitive Data types : to store simple values
- Non-Primitive Data types : to store complex values

Primitive Data Types


These are the data types of fixed size.

Data Type Meaning Size Range


(in Bytes)

byte 2’s complement integer 1 -128 to 127


short 2’s complement integer 2 -32K to 32K

int Integer numbers 4 -2B to 2B

long 2’s complement integer 8 -


9,223,372,036,85
(larger values) 4,775,808
to
9,223,372,036,85
4,775,807

float Floating-point 4 Upto 7 decimal


digits

double Double Floating-point 8 Upto 16


decimal digits

char Character 2 a, b, c ..
A, B, C ..
@, #, $ ..

bool Boolean 1 True, false

Non-Primitive Data Types


These are of variable size & are usually declared with a ‘new’ keyword.

Eg : String, Arrays

String name = new String("Aman");


int[] marks = new int[3];
marks[0] = 97;
marks[1] = 98;
marks[2] = 95;

3. Constants
A constant is a variable in Java which has a fixed value i.e. it cannot be assigned a
different value once assigned.

imports java.utils.*;

public class Main {

public static void main(String[] args) {


// Constants
final float PI = 3.14F;
}
}

Homework Problems
1. Try to declare meaningful variables of each type. Eg - a variable named age
should be a numeric type (int or float) not byte.
2. Make a program that takes the radius of a circle as input, calculates its
radius and area and prints it as output to the user.
3. Make a program that prints the table of a number that is input by the user.
(HINT - You will have to write 10 lines for this but as we proceed in the
course you will be studying about ‘LOOPS’ that will simplify your work A
LOT!)

KEEP LEARNING & KEEP PRACTICING :)

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