Java Programming Workshop

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Application Fundamentals

Types of Software
https://whatis.techtarget.com/definition/system-software
System Software
https://searchsoftwarequality.techtarget.com/definition/application
Application Software
Application
Software
Games, MS Office,
Browser etc.
System Software
Operating System,
Tools & Utilities,
Compilers
Hardware
Disk, CPU, RAM

Types of
Application
Web Desktop Mobile
▪ Java
▪ .NET
▪ PHP
▪ Python
▪ Others
▪ Java
▪ .NET
▪ Python
▪ Others
▪ Android (java, Kotlin)
▪ iOS (Swift)
L
a
n
g
u
a
g
e
s

We require
database to
store data

Driver
We require JDBC (Java
Database Connectivity) Driver
to perform operation with
Databases

It is intended to let application developers "write once,
run anywhere" (WORA), meaning that compiled Java
code can run on all platforms that support Java without
the need for recompilation.

Java is Object Oriented

public class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello, World!");
}
}
Compile: javac filename.java
Run: java ClassName

javac HelloWorld.java
Compile:
java HelloWorld
Run:

This is the entry point of our Java program. the main method has to have this
exact signature in order to be able to run our program.
public again means that anyone can access it.
static means that you can run this method without creating an instance of
HelloWorld.
void means that this method doesn't return any value.
main is the name of the method.

• The HelloWorld.java file is known as source code file.
• It is compiled by invoking tool named javac.exe, which compiles the source code into a .class file.
• The .class file contains the bytecode which is interpreted by java.exe tool.
• java.exe interprets the bytecode and runs the program.

Package in Java
A package in Java is used to group related classes. Think of it as a folder
in a file directory. We use packages to avoid name conflicts, and to
write a better maintainable code. Packages are divided into two
categories:

Java Packages
• Built-in Packages (packages from the Java API)
• User-defined Packages (create your own packages)

Importing packages
import package.name.Class; // Import a single class
import package.name.*; // Import the whole package

Scanner Class in Java
import java.util.Scanner;
class MyClass {
Scanner myObj = new Scanner(System.in);
System.out.println("Enter username");
String userName = myObj.nextLine();
System.out.println("Username is: " + userName);
}
}

To import a whole package,
end the statement with an asterisk sign (*).
import java.util.*;

Methods in Java
• A method is a block of code which only runs when it is called.
• You can pass data, known as parameters, into a method.

modifier returnType nameOfMethod (Parameter List) {
// method body
}

Variables and Types
Although Java is object oriented, not all types are objects. It is built on top of basic variable types
called primitives.
List of all primitives in Java:
byte (number, 1 byte)
short (number, 2 bytes)
int (number, 4 bytes)
long (number, 8 bytes)
float (float number, 4 bytes)
double (float number, 8 bytes)
char (a character, 2 bytes)
boolean (true or false, 1 byte)

Java is a strong typed language, which means variables need to
be defined before we use them.
int myNumber;
myNumber = 5;

String is not a primitive. It's a real type, but Java has special treatment for String.
// Create a string with a constructor
String s1 = new String("Who let the dogs out?");
// Just using "" creates a string, so no need to write it the previous way.
String s2 = "Who who who who!";
// Java defined the operator + on strings to concatenate:
String s3 = s1 + s2;
int num = 5;
String s = "I have " + num + " cookies"; //Be sure not to use ""
with primitives.
Can also concat string to primitives:

Operator
Operator in java is a symbol that is used to perform operations

Operator Precedence
Operators Precedence
postfix expr++ expr--
unary ++expr --expr +expr -expr ~ !
multiplicative * / %
additive + -
shift << >> >>>
relational < > <= >= instanceof
equality == !=
bitwise AND &
bitwise exclusive OR ^
bitwise inclusive OR |
logical AND &&
logical OR ||
ternary ? :
assignment = += -= *= /= %= &= ^= |= <<= >>= >>>=

Simple Assignment Operator
=

Arithmetic Operators
+ Additive operator (also used for String concatenation)
- Subtraction operator
* Multiplication operator
/ Division operator
% Remainder operator

Unary Operators
+ Unary plus operator; indicates positive value (numbers are
positive without this, however)
- Unary minus operator; negates an expression
++ Increment operator; increments a value by 1
-- Decrement operator; decrements a value by 1
! Logical complement operator; inverts the value of a boolean

Equality and Relational Operators
== Equal to
!= Not equal to
> Greater than
>= Greater than or equal to
< Less than
<= Less than or equal to

&& Conditional-AND
|| Conditional-OR
?: Ternary (shorthand for if-then-else statement)

Bitwise and Bit Shift Operators
~ Unary bitwise complement
<< Signed left shift
>> Signed right shift
>>> Unsigned right shift
& Bitwise AND
^ Bitwise exclusive OR
| Bitwise inclusive OR

Conditionals
Java uses boolean variables to evaluate conditions. The boolean values true
and false are returned when an expression is compared or evaluated. For
example:
int a = 4;
boolean b = a == 4;
if (b) {
System.out.println("It's true!");
}

The if-then Statement
The if-then statement is the most basic of all the control flow statements
void applyBrakes() {
// the "if" clause: bicycle must be moving
if (isMoving){
// the "then" clause: decrease current speed
currentSpeed--;
}
}

If this test evaluates to false (meaning that the bicycle is not in motion),
control jumps to the end of the if-then statement.
// the "if" clause: bicycle must be moving
if (isMoving){
// the "then" clause: decrease current speed
currentSpeed--;
}
}

The if-then-else Statement
if (isMoving) {
currentSpeed--;
} else {
System.err.println("The bicycle has already stopped!");
}
}

class IfElseDemo {
int testscore = 76;
char grade;
if (testscore >= 90) {
grade = 'A';
} else if (testscore >= 80) {
grade = 'B';
grade = 'C';
grade = 'D';
} else {
grade = 'F';
}
System.out.println("Grade = " + grade);
}
}

The switch Statement
A switch works with the byte, short, char, and int primitive
data types.
It also works with enumerated types (discussed in Enum
Types), the String class, and a few special classes that wrap
certain primitive types: Character, Byte, Short, and Integer

public class SwitchDemo {
int month = 8;
String monthString;
switch (month) {
case 1: monthString = "January";
break;
case 2: monthString = "February";
break;
case 3: monthString = "March";
break;
case 4: monthString = "April";
break;

case 5: monthString = "May";
break;
case 6: monthString = "June";
break;
case 7: monthString = "July";
break;
case 8: monthString = "August";
break;
case 9: monthString = "September";
break;
case 10: monthString = "October";
break;
case 11: monthString = "November";
break;
case 12: monthString = "December";
break;
default: monthString = "Invalid month";
break;
}
System.out.println(monthString);
}

• The body of a switch statement is known as a switch block.
• A statement in the switch block can be labeled with one or
more case or default labels.
• The switch statement evaluates its expression, then executes
all statements that follow the matching case label.

The while and do-while Statements
The while statement continually executes a block of statements while a
particular condition is true. Its syntax can be expressed as:
while (expression) {
statement(s)
}

The while statement evaluates expression, which must return a
boolean value.

class WhileDemo {
public static void main(String[] args){
int count = 1;
while (count < 11) {
System.out.println("Count is: " + count);
count++;
}
}
}

Do…while
class DoWhileDemo {
int count = 1;
do {
System.out.println("Count is: " + count);
count++;
} while (count < 11);
}
}

The for Statement
The for statement provides a compact way to iterate over a range of
values. Programmers often refer to it as the "for loop" because of the
way in which it repeatedly loops until a particular condition is satisfied.

for (initialization; termination; increment) {
statement(s)
}

class ForDemo {
for(int i=1; i<11; i++){
System.out.println("Count is: " + i);
}
}
}

Enhanced for
class EnhancedForDemo {
int[] numbers = {1,2,3,4,5,6,7,8,9,10};
for (int item : numbers) {
System.out.println("Count is: " + item);
}
}
}

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