JAVA WORKSHOP(DAY 3) 1234567889999999.pptx

Noida Institute of Engineering and
Technology, Greater Noida
JAVA TRAINING
Mr. Sumit Kumar
Subject code-BMCA0253
OOT using JAVA
DATE - 10/04/2024 TIME – 9:00 TO 05:00

2
Java Array
 Java array is an object the contains elements of similar data
type. It is a data structure where we store similar elements.
 Array holds a fixed number of elements.
 Length of an array is specified when an array is created. Once
length of an array is specified it remains fixed.
 Array in Java is index based and the index starts from 0. So
the first element is stored in the array at index 0.
 Elements in Java array are always numbered from 0 to (n –
1) where n is the individual elements in the array.
 They are dynamic, created on the heap memory.
 Array objects implement Cloneable and Serializable
interfaces.
 To declare an array, define the variable type with square
brackets:[]

4
• An array is a container object that holds a fixed number of values of a single
type.
• The length of an array is established when the array is created. After creation,
its length is fixed.
• As we know Array is a data structure where we store similar elements and
Array a starts from index 0.
• Each item in an array is called an element, and each element is accessed by its
numerical index.
• Since arrays are objects in Java, we can find their length using member length.
• A Java array variable can also be declared like other variables with [] after the
data type.
• The variables in the array are ordered and each has an index beginning from
0.
• Java array can be also be used as a static field, a local variable or a method
parameter.
• The size of an array must be specified by an int value and not long or short

6
Advantage of Java Array
Code Optimization: It makes the code optimized, we can retrieve or
sort the data easily.
Random access: We can get any data located at any index position.
Disadvantage of Java Array
Size Limit: We can store the only fixed size of elements in the array. It
doesn't grow its size at runtime. To solve this problem,
collection framework is used in java.

9
Types of Array in java
Single Dimensional Array
Multidimensional Array

11
Declaring a Variable to Refer to an Array
// this form is discouraged
float anArrayOfFloats[];
int[] anArray;
1.An array's type is written as type[], where type is the data type of
the contained elements; the brackets are special symbols
indicating that this variable holds an array. The size of the array is
not part of its type (which is why the brackets are empty).
Creating an Array
Int[] anArray = new int[10];
String[] anArrayOfStrings = new String[10];
Object[] anArrayOfObjects = new Object[10];

13
• Multidimensional array in java
 In such case, data is stored in row and column based index (also known
as matrix form).
Syntax to Declare Multidimensional Array in java
dataType[][] arrayRefVar;
(or)
dataType arrayRefVar[][];
(or)
dataType []arrayRefVar[];

14
 Example to instantiate Multidimensional Array in java
int[][] arr=new int[3][3]; //3 row and 3 column
 Example to initialize Multidimensional Array in java
arr[0][0]=1;
arr[0][1]=2;
arr[0][2]=3;
arr[1][0]=4;
arr[1][1]=5;
arr[1][2]=6;
arr[2][0]=7;
arr[2][1]=8;
arr[2][2]=9;

15
 Example of Multidimensional java array
class Testarray3{
public static void main(String args[]){
//declaring and initializing 2D array
int arr[][]={{1,2,3},{2,4,5},{4,4,5}};
//printing 2D array
for(int i=0;i<3;i++){
for(int j=0;j<3;j++){
System.out.print(arr[i][j]+" ");
}
System.out.println();
}
}
}
Output :-
1 2 3
2 4 5
4 4 5

16
OOPs (Object-Oriented Programming System)
• OOPs (Object-Oriented Programming System)Object
means a real-world entity such as a pen, chair, table,
computer, watch, etc. Object-Oriented Programming is a
methodology or paradigm to design a program using
classes and objects. It simplifies software development
and maintenance by providing some concepts:
• Object
• Class
• Inheritance
• Polymorphism
• Abstraction
• Encapsulation

17
Object
• The Object is the real-time entity having some state and behavior. In
Java, Object is an instance of the class having the instance variables
as the state of the object and the methods as the behavior of the
object. The object of a class can be created by using the new keyword
in Java Programming language.
• 1. An object is a real-world entity.
• 2. An object is a runtime entity.
• 3. The object is an entity which has state and behavior.
• 4. The object is an instance of a class.
• object in Java is the physical entity
• Real-world examples
• Dogs have state (name, color, breed, hungry) and behavior (barking,
fetching, wagging tail). Chair, Bike, Marker, Pen, Table, Car, Book,
Apple, Bag etc. It can be physical or logical (tangible and intangible).

18
• Apart from these concepts, there are some other
terms which are used in Object-Oriented design:
• - Coupling
• - Cohesion
• - Association
• - Aggregation
• - Composition

20
class
A class is a group of objects which have common properties.
It is a template or blueprint from which objects are created.
In short, a class is the specification or template of an object.
• class in Java is a logical entity only.
• A class is a template or blueprint from which objects are
created. So, an object is the instance(result) of a class.
• A class in Java can contain:
• Fields
• Methods
• Constructors
• Blocks
• Nested class and interface

22
1.class <class_name>{
2. method;
3. field;
4.}

24
//Java Program to illustrate how to define a class and fields
//Defining a Student class.
class Student{
//defining fields
int id;//field or data member or instance variable
String name;
//creating main method inside the Student class
//Creating an object or instance
Student s1=new Student();//creating an object of Student
//Printing values of the object
System.out.println(s1.id);//
accessing member through reference variable
System.out.println(s1.name);
}
}

25
//Java Program to demonstrate having the main method in
//another class
//Creating Student class.
class Student{
int id;
String name;
}
//
Creating another class TestStudent1 which contains the main method
class TestStudent1{
Student s1=new Student();
System.out.println(s1.id);
System.out.println(s1.name);
}
}

26
class Student{
int id;
String name;
}
class TestStudent2{
s1.id=101;
s1.name="Sonoo";
System.out.println(s1.id+" "+s1.name);//
printing members with a white space
}
}

27
class Student{
int rollno;
String name;
void insertRecord(int r, String n){
rollno=r;
name=n;
}
void displayInformation(){System.out.println(rollno+" "+name);}
}
class TestStudent4{
s1.insertRecord(111,"Karan");
s2.insertRecord(222,"Aryan");
s1.displayInformation();
}
}

28
Student2 s1=new Student2();
Student2 s2=new Student2();
s1.insertRecord(111,"Karan");
s2.insertRecord(222,"Aryan");
}
}
111 Karan
222 Aryan
OUTPUT

JAVA WORKSHOP(DAY 3) 1234567889999999.pptx

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