This document discusses variables and data types in Java. It covers: - Different Java variable types like String, int, float, char, and boolean - Identifiers for naming variables and rules for identifiers - Declaring and assigning variables - Concatenating strings - Taking user input using the Scanner class - Mathematical operators for performing calculations

1. VARIABLE AND DATATYPES

2. VARIABLES
Used to store up temporary data to be used in our program’s runtime
DATA TYPES
Type of Data Inside the variable

3. JAVA VARIABLE
In Java, there are different types of variables, for example:
String - stores text, such as "Hello". String values are surrounded by double quotes
int - stores integers (whole numbers), without decimals, such as 123 or -123
float - stores floating point numbers, with decimals, such as 19.99 or -19.99
char - stores single characters, such as 'a' or 'B'. Char values are surrounded by
single quotes
boolean - stores values with two states: true or false 1/0 close/open

4. IDENTIFIERS
Name of variables that the programmer indicated, it is used to read and write the
variables
Rules of Identifier:
1. You cannot use special any special character other than underscore(_)
2. You cannot use whitespace
3. You cannot use number alone
4. You can use number but with letter

5. Declaring (Creating) variables
DATA TYPE IDENTIFIER;
DATA TYPE IDENTIFIER= value;

6. Reassigning Variable
Syntax:
identifier = value;

7. System.out.printlin();
String name = “Juan”;
System.out.printlin(name);
Int number = 5;
System.out.println(number);

8. Concatanation
The process of joining Strings together with the plus operator
Concatenation NOT Concatenation
“Hello” + “World” 2 + 3
“2” + “3” ‘a’ + 3
‘a’ =“b”
2 = “3”
You can concatenate inside the variable or on the print statement

9. ACTIVITY #2 Sentence Builder
Create a Program that will only require a programmer to change the variable value in order to create a
dynamic sentence using the sentence on the sample output:
Please take note Bold word indicate a variables
Hi! My name is :Your Name
I am: Your Age
My section is INF/Comscie : A
My GPA is 3.25
My Blood type is : O

10. USER INPUT
BUILT-IN PACKAGES
Java API has many pre-written classes to help the programmer manages input,
databases and other
IMPORTING PACKAGES

11. IMPORTING PACKAGES
Import Specific Class
import packagesname.classname
Import Whole Packages
import packagesname.*

12. import Java.util.scanner
A class in the java.util packages that
helps programmer to handle inputs
from the user

13. Mathematical Operators

14. User Input
String x;
Scanner s = new scanner( System.in); //new scanner
System.out.println(“Enter your Name:”);
X = s.nextline(); //read user input
System.out.print(“You are “+ age “Years Old”);
X = s.nextint();
System.out.println(x);

15. Input Types

16. Sample Syntax
Int x=10;
Int x=5;
System.out.println(x+y);
System.out.println(x/y);
System.out.println(x%y);

17. Activity #3 One function Calculator
Create a program that will make a user input the 2 numbers and perform the one
Arithmetic operators excluding increment and decrement. Sample output:
Num1: 5
Num2: 5
Result: 5+5=10