04-CCFP4.0_OOP Using Java

8/20/2019 04-CCFP4.0_OOP Using Java

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OO programming using Java

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Copyright © 2013-2014, Infosys Limited ConfidentialConfidential

Copyright Guideline

© 2013 Infosys Limited, Bangalore, India. All Rights Reserved.

Infosys believes the information in this document is accurate as of its publication date; such

information is subject to change without notice. Infosys acknowledges the proprietary rights of

other companies to the trademarks, product names and such other intellectual property rights

mentioned in this document. Except as expressly permitted, neither this documentation nor

any part of it may be reproduced, stored in a retrieval system, or transmitted in any form or by

any means, electronic, mechanical, printing, photocopying, recording or otherwise, without the

prior permission of Infosys Limited and/ or any named intellectual property rights holders

under this document.

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Confidential Information

This Document is confidential to Infosys Limited. This document contains information and data that

Infosys considers confidential and proprietary (“Confidential Information”).

Confidential Information includes, but is not limited to, the following:

Corporate and Infrastructure information about Infosys

Infosys’ project management and quality processes

Project experiences provided included as illustrative case studies

Any disclosure of Confidential Information to, or use of it by a third party, will be damaging to Infosys.

Ownership of all Infosys Confidential Information, no matter in what media it resides, remains with

Infosys.

Confidential information in this document shall not be disclosed, duplicated or used – in whole or in part –

for any purpose other than reading without specific written permission of an authorized representative of

Infosys.

This document also contains third party confidential and proprietary information. Such third party

information has been included by Infosys after receiving due written permissions and authorizations fromthe party/ies. Such third party confidential and proprietary information shall not be disclosed, duplicated

or used – in whole or in part – for any purpose other than reading without specific written permission of

an authorized representative of Infosys.

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Course Information

Course Code: CCFP4.0-OOP

Course Name: OO programming using Java

Document Number: OOP-04

Version Number: V4.0

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Recap

• Object Oriented Fundamentals

– Java Architecture

– Variables in detail

– Reference Variables & Objects in Memory

– Methods – Parameter Passing Techniques

– ‘this’ reference

• Data Structures

– Linear

– Non–linear

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OO Fundamentals


anywhere!


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OO Fundamentals

• Object Oriented Fundamentals

– Arrays – Revisit

– Strings

– Constructors

– “static” keyword

– Command Line Arguments

• Algorithm Design Techniques

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Arrays - Revisit


anywhere!


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Arrays (1 of 4)

• An array is a collection of similar data in contiguous locations of memory having

the same name

• Arrays can be used to store data belonging to primitive data types and reference

types

• Arrays are created dynamically in Java

• Types of Arrays

– Single Dimensional Arrays

– Multi-Dimensional Arrays

•

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Arrays (2 of 4)

Single Dimensional Arrays :

• An array with one dimension (one row) is called a single dimensional array

• Different ways of creating and initializing an array are given below – Method 1:

– Method 2:

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long telephoneNos[] = new long[3];

telephoneNos[0] = 48214280200L;

telephoneNos[1] = 9901911334L;telephoneNos[2] = 4821710601L;

long [] telephoneNos= {48214280200L, 9901911334L, 4821710601L};

Where will the memory be

allocated for this array?

Note that the [] can be placed

before or after the array name


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Arrays (3 of 4)

• Array elements will be stored dynamically in the heap

• Array elements will be initialized to default values of respective type if not

explicitly initialized

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Stack

4821428020

9901911334

Heap

telephoneNos

long[]

4821710601

Note: Here it is assumed that the declaration of telephoneNos is done inside the main () method.

If the same is an instance variable, the reference would be stored in heap


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Arrays (4 of 4)

• Length property – Length property represents the size of an array

– Length of an array can be identified using the below statement

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Quiz: OO Fundamentals –Assignment 47

arrayname.length

Demo: OO Fundamentals - Assignment 48


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Strings


anywhere!


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Strings (1 of 3)

• A set of related characters can be represented using a string

• In Java, this is done with the help of a built in class called String• Creation and Initialization of a String object

– Method 1: Creating an object of String using new operator

– Method 2: Assigning a group of characters into a String object

– Method 3: Combining both the statements in Method 2

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Guided Activity: OO Fundamentals - Assignment 49

String customerName = new String(“Jack”);

String customerName;

customerName = “Jack”;

String customerName = “Jack”;

Where will the

memory be

allocated?


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Strings (2 of 3)

• customerName is the reference variable referring to a String object

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Stack

Jack

Heap

customerName

Note: Here it is assumed that the declaration of customerName is done inside the main () method.

If the customerName is an instance variable, then it would be stored in heap

Quiz: OO Fundamentals - Assignment 50


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Strings (3 of 3)

• String class contains many methods which facilitate operations on the Strings

– length()

– concat()

– equals()

– equalsIgnoreCase() etc

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Strings - Revisit

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Quiz: OO Fundamentals - Assignment 52


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OO Constructs - I


anywhere!


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Constructors


anywhere!


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Constructor

• Constructor is a special method that has the same name as that of a class

• The constructor is used to initialize the instance variables of the class

• Types of constructors:

– Default constructor

– Parameterized constructor

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Guided Activity: OO Fundamentals - Assignment 53




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‘static’ keyword


anywhere!


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static keyword (1 of 2)

• The concept of static is used whenever data which is common to the objects of

the class is required

• In Java, static keyword can be used in 3 scenarios:

– static variables:

• Also called class variables and are initialized at class load time

– static methods• Used for accessing static variables.

• Can be invoked using class name or object reference

– static blocks

• Block of statements in a java class which gets executed when a class is first loaded in memory

• Can have any number of static blocks in which case it gets executed in the order in which it is

written

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static keyword (2 of 2)

• Static methods and static blocks can access only other static data members and

methods directly

• Non static variable cannot be accessed directly inside a static method or static

block

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Command Line Arguments

• To pass an argument to the main method

• The String[] (array of String objects) contains the command line arguments that

are passed ,when the program is invoked

• To convert command line arguments passed as String to integer use

Integer.parseInt() method

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public static void main(String [] args){ }



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Revisiting main() method

• main() is declared as public so it can be accessed from anywhere

• static allows main( ) to be called without having to instantiate a particular instance

of the class

• This is required because the main( ) is called by the Java interpreter before any

objects are created

• void informs the compiler that main( ) does not return any value

• The parameter passed to the main() i.e. String args[] facilitates input throughcommand line arguments

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Retail Application – we have learnt

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1. Arrays

2. Strings

3. Constructors

4. ‘static’ keyword

5. Command Line Arguments


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Algorithm Design Techniques


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Algorithm design techniques - Introduction

• A problem can be solved by using different logical approaches / algorithms

• The analysis of various approaches and the choice of a particular approach is a

key step in the solution of a given problem

• The choice of a particular approach may depend on factors like the efficiency in

terms of time, memory requirements or how optimal solution is.

• Algorithm design techniques are used to implement an approach based on

factors that are important for a solution

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Guided Activity: Algorithm Design Techniques – Assignment 58


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Algorithm design techniques

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Algorithm Design Techniques

are Brute Force Approach

Exhaustively try every possibility

Divide and Conquer Approach

Split into smaller problems and solve

Greedy Approach

First solve the problem that requires least effort

Dynamic Programming Approach

Identify overlapping sub problems and reuse their solutions


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Brute force approach

• Intuitive / straight forward problem solving approach

• Directly based on the problem statement and the concept - ”Just Do It”

• Covers a wide range of problems under its gamut

• Simple but may be inefficient in certain cases

• Examples include bubble sort, linear search etc.,

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Brute force approach: Example – Linear Search and

Bubble Sort

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Demo: Algorithm Design Techniques – Assignment 59

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Divide and conquer approach

• Divide the problem into two or more independent subproblems

• Solve the subproblems and combine solutions of the subproblems to get overall

solution

• Examples include binary search, hash table etc.,

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Divide and conquer approach: Example - Binary Search

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Demo: Algorithm Design Techniques – Assignment 60-A


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Greedy approach

• Primarily used in Optimization problems

• Constructs solution through a sequence of steps where each step is considered

to be a partial solution. This is extended to get the complete solution

• Choice of each step must be

– Locally optimal

– Feasible

– Irrevocable

• Examples include currency change making, travelling salesman problem etc.,


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© 2013Infosys Limited, Bangalore, India. All Rights Reserved. Infosys believes theinformation in thisdocument is accurate as of its publication date; such information is subject to changewithout notice. Infosys acknowledgesthe proprietaryrights of other companiesto thetrademarks,product names andsuch other intellectual property rightsmentioned in this document.Exceptasexpressly permitted,neither thisdocumentation nor anypart of it maybe reproduced,stored in a retrievalsystem,or transmittedin anyform or by anymeans, electronic, mechanical,printing,photocopying,recordingor otherwise,withoutthe prior permissionof Infosys Limitedand/or anynamedintellectual property rightsholdersunderthis document.

Thank You


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Appendix


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Arrays (2 of 2) – Self Study

Multi-dimensional Array

– No. of rows can be obtained as follows:

– No. of columns in a row can be obtained as follows:

– Consider the array given below:

arrayname[rownumber].length

char[][] arrNum={{‘a’,’2’},{‘\0’,’I’}}

arrayname.length

arrNum.length, i.e 2

arrNum[1].length, i.e 2

What is the size of the array-

arrNum?

How many columns are there

in second row (index number

one) of the array- arrNum?

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Greedy approach

• Primarily used in Optimization problems

• Constructs solution through a sequence of steps where each step is considered

to be a partial solution. This is extended to get the complete solution

• Choice of each step must be

– Locally optimal

– Feasible

– Irrevocable

• Examples include currency change making, travelling salesman problem etc.,

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04-CCFP4.0_OOP Using Java