Arrays are used in java to holding more.pptx

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Copyright © 2021 Infogain Corporation. All Rights Reserved.
Array in Java
Part-001

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Objectives
◌ Comparison of various programming techniques
◌ Introduction to Object Oriented Concepts
◌ What is an Object
◌ Abstraction, Encapsulation, Message Passing
◌ Class, Access Specifiers, Examples
◌ Advanced Object-Oriented Concepts
◌ Relationships
◌ Inheritance
◌ Abstract Classes and Polymorphism
◌ Object Oriented Design Methodology
◌ Trends in OO Technology

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Arrays in Java
◌ Object Here, we have assumed that a restaurant will have only one contact number.
◌ What if the restaurant has multiple contact numbers?
◌ How can we store multiple contact numbers of a restaurant?
◌ One solution to this problem is to create more instance variables to store multiple contact numbers and
initialize it with different values. After implementing, the Restaurant class will look like this.

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Arrays in Java
◌ In order to implement the previous requirement, we can use various collections in Java. Here, to implement
this requirement we will use one of the most common collection called Array.
◌ An array is a collection of values of the same data type, stored in contiguous memory locations and referred
by the same name. It holds a fixed number of values, decided at the time of array declaration.
◌ The last implementation of the Restaurant class had three different variables to store three different contact
numbers. The below diagram shows how the contact numbers are stored if they are present in different
variables and if they are stored in an array.

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Arrays in Java

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Arrays in Java
◌ In order to use array in Java, you need to declare an array along with a datatype. You can declare,
create and initialize an array in the following ways:
◌ Declaring and initializing the array in one line:
◌ Syntax:

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Arrays in Java
◌ In order to use array in Java, you need to declare an array along with a datatype. You can declare,
create and initialize an array in the following ways:
◌ Creating the array using new:
◌ Syntax:

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Arrays in Java
◌ Declaring and creating the array in different lines:
◌ Syntax:

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Accessing the elements of an array
◌ Each value stored in an array is called as an element. Each element in an array is accessed, stored and
retrieved using its position in the array, called index. Indexes in Java are zero-based, i.e., the valid range of
indexes for the elements of an array is from 0 to (size of Array-1).
long[] restaurantContacts = new long[3];
restaurantContacts [0] = 9992346725L; // Elements can be updated and accessed with
the help of index
restaurantContacts [1] = 9992346726L;
restaurantContacts [2] = 9992346727L;
System.out.println(restaurantContacts [1]) ;// Accessing and displaying the element
at the 1st index

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Accessing the elements of an array using for loop
◌ Instead of writing n number of lines to access n elements of an array, you can use different looping
constructs like for loop, for-each loop, etc.
◌ The below code shows how to access and display the elements of restaurantContacts with the help of for
loop.
public class Tester {
public static void main(String[] args) {
long[] restaurantContacts = { 9992346725L, 9992346726L, 9992346727L };
for (int index = 0; index < restaurantContacts.length; index++) {
// Accessing element at position index
System.out.println(restaurantContacts[index]);
}
}
}

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Accessing the elements of an array using for each loop
◌ Java also has another loop known as for-each loop to iterate over collections. This eliminates the use of
indexes. It displays the array elements one by one. It holds an array element in a variable and then
executes the body of the loop.
Syntax
for (dataType variable: array) {
//body of the loop
}
public class Tester {
public static void main(String[] args) {
long[] restaurantContacts = { 9992346725L, 9992346726L, 9992346727L };
for (long contactNumber : restaurantContacts) {
System.out.println(contactNumber);
}
}
}

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Multi-dimensional Array
◌ Multi-dimensional arrays are arrays of arrays with each element of the array holding the reference of other
arrays.
◌ A multi-dimensional array is created by appending one set of square brackets ([]) per dimension..
◌ Let's see a simple example to declare, instantiate, initialize and display a 2-dimensional (2D) array.
◌ Syntax for creating 2D array:
dataType[][] arrayVarName = new dataType[rowsize][columnsize];

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//Here, the row size is 7, and the column size is 2
//The 0th index stores the Max temperature and 1st index stores the Min temperature
int[][] dayWiseTemperature = new int[7][2];
dayWiseTemperature[0][0]=29; // Initialization
dayWiseTemperature[0][1]=21;
//and so on
//Another way of creating and initializing 2D array
int[][] dayWiseTemperature = new int[][] {
{29,21},
{24,23},
{26,22},
{28,23},
{29,24},
{23,20},
{29,21}
};

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Points to remember
◌ Some of the important points that you should be knowing about arrays are:
◌ An array is a collection of similar data in contiguous memory locations referred by the same name
◌ Can be used to store data of primitive as well as reference types
◌ Holds a fixed number of values, determined at the time of array declaration
◌ Array index always starts from zero
◌ The length attribute of an array can be used to get its size
◌ Once initialized, the size of an array cannot be changed

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