Application
Programming
Hend Alkittawi

Java Basics
Introduction to Java Concepts and
User-defined Java Classes

CONCEPTS

JAVA

OBJECT

- Released in early 1990s

- Defined by a class

- Object-oriented

- A class is a reusable

- Java SE, Java EE, Java ME

software components
- Non-primitive data type

CONCEPTS

JAVA APIs
- Application Programming
Interfaces
- Collections of existing
classes and methods in the
Java class libraries

JDK
- Java Development Kit
- Includes compiler, loader,
debugger, JRE, and other
tools for Java development

CONCEPTS

JVM
- Java Virtual Machine
- A part of the JRE that

IDE
- Integrated Development
Environment

executes bytecodes.

- A software that provides

- Bytecodes are platform

comprehensive facilities

independent (portable)

for software development.

WHY DO WE USE OBJECTS?
●

Let us discuss the difference between
○

Write a program to read n number of values in an array and
display them in reverse order.

○

Write a program to calculate x raised to the power n (xn).

○

Write a program to swap two numbers.

and
○

Small Scale Applications

OBJECT ANALOGY

BLUEPRINTS

My Car
color, …
accelerate, …

Your Car

Some Car

color, …
accelerate, …

color, …
accelerate, …

JAVA OBJECTS
public class Car {

Class Declaration

private int colorID;
private double speed;
public void setSpeed(int s){
speed = s;
}
public void accelerate(){
speed = speed + 70;
}

Attributes / Instance Variable(s)

Behaviors / Method(s)

public static void main(String[] args){
Car myCar = new Car();
myCar.setSpeed(50);
}
}

Car.java

Instantiation (building a Car object)

OBJECT ANALOGY

BIOLOGICAL
CLASSIFICATION

My Dog
breed, …
bark, …

Your Dog
breed, …
bark, …

Some Dog
breed, …
bark, …

JAVA OBJECTS
public class Dog {

Class Declaration

private int breedID;

Attributes / Instance Variable(s)

public void bark(){
System.out.println(＂Woof＂);
}

Behaviors / Method(s)

Dog.java

public static void main(String[] args){
Dog myDog = new Dog();
Instantiation (building a Dog obj)
myDog.bark();
}
}

THE String CLASS
-

The char primitive type stores one character of the Unicode
character set.

-

-

A string is a sequences of characters.
-

can be 0 or more characters long

-

"" is the empty string

The String class facilitates handling multiple characters at
once.

-

A String object can be declared in order to work with strings
String someStringObject = new String();
someStringObject = "HI";

THE String CLASS
-

Many String manipulation methods are available, here are some:
-

split() method to get an array of Strings from a String, based
on a delimiter. This object method takes a delimiter as a
parameter.

-

trim() method to clear off any additional space from the text.
This object method takes no parameters.

-

charAt() method to get the character at an index in the string
[starting with index 0]. This object method takes an index as
a parameter.

-

equals() method to check if two Strings contain the same text.
This object method takes a String object as a parameter.

THE String CLASS
-

Java also treats string literals as objects
-

-

A string literal is a quoted string: "Sam I am", "Hi", …, etc.

Examples:
String strObj = "This is \"a\" String";
strObj.charAt(0);
"HI

".trim();

escape sequence

"Hello".equals(strObj);
●

Note how we can create/work with string literals as String
objects.

JAVA OBJECTS
public class Dog {
private int breedID;
private String name;
public void bark(String dogBark){
System.out.println(dogBark);
}

}

public static void main(String[] args){
Dog myDog = new Dog();
myDog.bark(＂Woof＂);
}

Dog.java

Class Activity
public class SimpleLocation {
private double latitude;
private double longitude;
public void setLocation(double lat, double lon){
latitude = lat;
longitude = lon;
}

}

public static void main(String[] args){
SimpleLocation utsa = new SimpleLocation();
utsa.setLocation(32.9, -117.2);
}

What is
the value
of
longitude
?

DO YOU HAVE ANY
QUESTIONS?

THANK
YOU!

@

hend.alkittawi@utsa.edu

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