This document provides an overview of a Java programming fundamentals course. It discusses the history and development of Java, how Java works, and some of its core features. Some key points:
- Java was created in the early 1990s by James Gosling at Sun Microsystems to be platform independent through the use of bytecode and the Java Virtual Machine.
- A Java program consists of classes that contain methods and can create objects. Everything must be contained within a class.
- The document reviews Java's basic data types including primitives like int and double, as well as classes. It also covers expressions, control structures like if/else statements and loops, and built-in classes like String and Math.
A web browser takes you anywhere on the internet, letting you see text, images and video from anywhere in the world. ... The web is a vast and powerful tool. Over .
Miller Columns (used in iPhone and Mac Finder) are an elegant way of displaying and navigating a tree. This talk describes a JavaScript implementation of Miller Columns, and why JavaScript needs modules and a standard library.
A web browser takes you anywhere on the internet, letting you see text, images and video from anywhere in the world. ... The web is a vast and powerful tool. Over .
Miller Columns (used in iPhone and Mac Finder) are an elegant way of displaying and navigating a tree. This talk describes a JavaScript implementation of Miller Columns, and why JavaScript needs modules and a standard library.
1 Project 2 Introduction - the SeaPort Project seri.docxhoney725342
1
Project 2
Introduction - the SeaPort Project series
For this set of projects for the course, we wish to simulate some of the aspects of a number of Sea Ports.
Here are the classes and their instance variables we wish to define:
SeaPortProgram extends JFrame
o variables used by the GUI interface
o world: World
Thing implement Comparable <Thing>
o index: int
o name: String
o parent: int
World extends Thing
o ports: ArrayList <SeaPort>
o time: PortTime
SeaPort extends Thing
o docks: ArrayList <Dock>
o que: ArrayList <Ship> // the list of ships waiting to dock
o ships: ArrayList <Ship> // a list of all the ships at this port
o persons: ArrayList <Person> // people with skills at this port
Dock extends Thing
o ship: Ship
Ship extends Thing
o arrivalTime, dockTime: PortTime
o draft, length, weight, width: double
o jobs: ArrayList <Job>
PassengerShip extends Ship
o numberOfOccupiedRooms: int
o numberOfPassengers: int
o numberOfRooms: int
CargoShip extends Ship
o cargoValue: double
o cargoVolume: double
o cargoWeight: double
Person extends Thing
o skill: String
Job extends Thing - optional till Projects 3 and 4
o duration: double
o requirements: ArrayList <String>
// should be some of the skills of the persons
PortTime
o time: int
Eventually, in Projects 3 and 4, you will be asked to show the progress of the jobs using JProgressBar's.
2
Here's a very quick overview of all projects:
1. Read a data file, create the internal data structure, create a GUI to display the structure, and let
the user search the structure.
2. Sort the structure, use hash maps to create the structure more efficiently.
3. Create a thread for each job, cannot run until a ship has a dock, create a GUI to show the
progress of each job.
4. Simulate competing for resources (persons with particular skills) for each job.
Project 2 General Objectives
Project 2 - Map class, Comparator, sorting
Use the JDK Map class to write more efficient code when constructing the internal data
structures from the data file.
Implement SORTING using the Comparator interface together with the JDK support for sorting
data structures, thus sorting on different fields of the classes from Project 1.
Extend the GUI from Project 1 to let the user sort the data at run-time.
Documentation Requirements:
You should start working on a documentation file before you do anything else with these projects, and
fill in items as you go along. Leaving the documentation until the project is finished is not a good idea for
any number of reasons.
The documentation should include the following (graded) elements:
Cover page (including name, date, project, your class information)
Design
o including a UML class diagram
o classes, variables and methods: what they mean and why they are there
o tied to the requirements of the project
User's Guide
o how would a user start and run your pro ...
This presentation discusses the most neglected quality axis : code documentation. See good and bad examples, best practices on documenting code and why you should try not to ignore it :)
Presentation date: 2014-11-28
Place: Thessaloniki Java Meetup Group (SKG)
1 Project 2 Introduction - the SeaPort Project seri.docxhoney725342
1
Project 2
Introduction - the SeaPort Project series
For this set of projects for the course, we wish to simulate some of the aspects of a number of Sea Ports.
Here are the classes and their instance variables we wish to define:
SeaPortProgram extends JFrame
o variables used by the GUI interface
o world: World
Thing implement Comparable <Thing>
o index: int
o name: String
o parent: int
World extends Thing
o ports: ArrayList <SeaPort>
o time: PortTime
SeaPort extends Thing
o docks: ArrayList <Dock>
o que: ArrayList <Ship> // the list of ships waiting to dock
o ships: ArrayList <Ship> // a list of all the ships at this port
o persons: ArrayList <Person> // people with skills at this port
Dock extends Thing
o ship: Ship
Ship extends Thing
o arrivalTime, dockTime: PortTime
o draft, length, weight, width: double
o jobs: ArrayList <Job>
PassengerShip extends Ship
o numberOfOccupiedRooms: int
o numberOfPassengers: int
o numberOfRooms: int
CargoShip extends Ship
o cargoValue: double
o cargoVolume: double
o cargoWeight: double
Person extends Thing
o skill: String
Job extends Thing - optional till Projects 3 and 4
o duration: double
o requirements: ArrayList <String>
// should be some of the skills of the persons
PortTime
o time: int
Eventually, in Projects 3 and 4, you will be asked to show the progress of the jobs using JProgressBar's.
2
Here's a very quick overview of all projects:
1. Read a data file, create the internal data structure, create a GUI to display the structure, and let
the user search the structure.
2. Sort the structure, use hash maps to create the structure more efficiently.
3. Create a thread for each job, cannot run until a ship has a dock, create a GUI to show the
progress of each job.
4. Simulate competing for resources (persons with particular skills) for each job.
Project 2 General Objectives
Project 2 - Map class, Comparator, sorting
Use the JDK Map class to write more efficient code when constructing the internal data
structures from the data file.
Implement SORTING using the Comparator interface together with the JDK support for sorting
data structures, thus sorting on different fields of the classes from Project 1.
Extend the GUI from Project 1 to let the user sort the data at run-time.
Documentation Requirements:
You should start working on a documentation file before you do anything else with these projects, and
fill in items as you go along. Leaving the documentation until the project is finished is not a good idea for
any number of reasons.
The documentation should include the following (graded) elements:
Cover page (including name, date, project, your class information)
Design
o including a UML class diagram
o classes, variables and methods: what they mean and why they are there
o tied to the requirements of the project
User's Guide
o how would a user start and run your pro ...
This presentation discusses the most neglected quality axis : code documentation. See good and bad examples, best practices on documenting code and why you should try not to ignore it :)
Presentation date: 2014-11-28
Place: Thessaloniki Java Meetup Group (SKG)
Final project report on grocery store management system..pdfKamal Acharya
In today’s fast-changing business environment, it’s extremely important to be able to respond to client needs in the most effective and timely manner. If your customers wish to see your business online and have instant access to your products or services.
Online Grocery Store is an e-commerce website, which retails various grocery products. This project allows viewing various products available enables registered users to purchase desired products instantly using Paytm, UPI payment processor (Instant Pay) and also can place order by using Cash on Delivery (Pay Later) option. This project provides an easy access to Administrators and Managers to view orders placed using Pay Later and Instant Pay options.
In order to develop an e-commerce website, a number of Technologies must be studied and understood. These include multi-tiered architecture, server and client-side scripting techniques, implementation technologies, programming language (such as PHP, HTML, CSS, JavaScript) and MySQL relational databases. This is a project with the objective to develop a basic website where a consumer is provided with a shopping cart website and also to know about the technologies used to develop such a website.
This document will discuss each of the underlying technologies to create and implement an e- commerce website.
Democratizing Fuzzing at Scale by Abhishek Aryaabh.arya
Presented at NUS: Fuzzing and Software Security Summer School 2024
This keynote talks about the democratization of fuzzing at scale, highlighting the collaboration between open source communities, academia, and industry to advance the field of fuzzing. It delves into the history of fuzzing, the development of scalable fuzzing platforms, and the empowerment of community-driven research. The talk will further discuss recent advancements leveraging AI/ML and offer insights into the future evolution of the fuzzing landscape.
CFD Simulation of By-pass Flow in a HRSG module by R&R Consult.pptxR&R Consult
CFD analysis is incredibly effective at solving mysteries and improving the performance of complex systems!
Here's a great example: At a large natural gas-fired power plant, where they use waste heat to generate steam and energy, they were puzzled that their boiler wasn't producing as much steam as expected.
R&R and Tetra Engineering Group Inc. were asked to solve the issue with reduced steam production.
An inspection had shown that a significant amount of hot flue gas was bypassing the boiler tubes, where the heat was supposed to be transferred.
R&R Consult conducted a CFD analysis, which revealed that 6.3% of the flue gas was bypassing the boiler tubes without transferring heat. The analysis also showed that the flue gas was instead being directed along the sides of the boiler and between the modules that were supposed to capture the heat. This was the cause of the reduced performance.
Based on our results, Tetra Engineering installed covering plates to reduce the bypass flow. This improved the boiler's performance and increased electricity production.
It is always satisfying when we can help solve complex challenges like this. Do your systems also need a check-up or optimization? Give us a call!
Work done in cooperation with James Malloy and David Moelling from Tetra Engineering.
More examples of our work https://www.r-r-consult.dk/en/cases-en/
Vaccine management system project report documentation..pdfKamal Acharya
The Division of Vaccine and Immunization is facing increasing difficulty monitoring vaccines and other commodities distribution once they have been distributed from the national stores. With the introduction of new vaccines, more challenges have been anticipated with this additions posing serious threat to the already over strained vaccine supply chain system in Kenya.
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
COLLEGE BUS MANAGEMENT SYSTEM PROJECT REPORT.pdfKamal Acharya
The College Bus Management system is completely developed by Visual Basic .NET Version. The application is connect with most secured database language MS SQL Server. The application is develop by using best combination of front-end and back-end languages. The application is totally design like flat user interface. This flat user interface is more attractive user interface in 2017. The application is gives more important to the system functionality. The application is to manage the student’s details, driver’s details, bus details, bus route details, bus fees details and more. The application has only one unit for admin. The admin can manage the entire application. The admin can login into the application by using username and password of the admin. The application is develop for big and small colleges. It is more user friendly for non-computer person. Even they can easily learn how to manage the application within hours. The application is more secure by the admin. The system will give an effective output for the VB.Net and SQL Server given as input to the system. The compiled java program given as input to the system, after scanning the program will generate different reports. The application generates the report for users. The admin can view and download the report of the data. The application deliver the excel format reports. Because, excel formatted reports is very easy to understand the income and expense of the college bus. This application is mainly develop for windows operating system users. In 2017, 73% of people enterprises are using windows operating system. So the application will easily install for all the windows operating system users. The application-developed size is very low. The application consumes very low space in disk. Therefore, the user can allocate very minimum local disk space for this application.
Student information management system project report ii.pdfKamal Acharya
Our project explains about the student management. This project mainly explains the various actions related to student details. This project shows some ease in adding, editing and deleting the student details. It also provides a less time consuming process for viewing, adding, editing and deleting the marks of the students.
Industrial Training at Shahjalal Fertilizer Company Limited (SFCL)MdTanvirMahtab2
This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
Event Management System Vb Net Project Report.pdfKamal Acharya
In present era, the scopes of information technology growing with a very fast .We do not see any are untouched from this industry. The scope of information technology has become wider includes: Business and industry. Household Business, Communication, Education, Entertainment, Science, Medicine, Engineering, Distance Learning, Weather Forecasting. Carrier Searching and so on.
My project named “Event Management System” is software that store and maintained all events coordinated in college. It also helpful to print related reports. My project will help to record the events coordinated by faculties with their Name, Event subject, date & details in an efficient & effective ways.
In my system we have to make a system by which a user can record all events coordinated by a particular faculty. In our proposed system some more featured are added which differs it from the existing system such as security.
1. 12/20/2023 Fundamentals of Java Programming 1
Object Oriented Programming with Java
Fundamentals of Java Programming
Dr. Yogesh Deshmukh
2. 12/20/2023 Fundamentals of Java Programming 2
Agenda
Brief History of Java and overview of
language
Basic Features
Data Types
Expression and Operators
Expressions and Operators
Arrays
Methods
More Features
4. 12/20/2023 Fundamentals of Java Programming 4
A brief history of Java
– "Java, whose original name was Oak, was developed as a
part of the Green project at Sun. It was started in
December '90 by Patrick Naughton, Mike Sheridan and
James Gosling and was chartered to spend time trying to
figure out what would be the "next wave" of computing and
how we might catch it. They came to the conclusion that at
least one of the waves was going to be the convergence of
digitally controlled consumer devices and computers. “
Object Oriented Programming Language
– It follows object oriented methodology. That is it support
Class, Objects, Inheritance, Polymorphism, Data
Abstraction, Dynamic Binding, Exception Handling.
5. 12/20/2023 Fundamentals of Java Programming 5
How Java Works
Java's platform independence is achieved by the
use of the Java Virtual Machine
A Java program consists of one or more files with a
.java extension
– these are plain old text files
When a Java program is compiled the .java files
are fed to a compiler which produces a .class file
for each .java file
The .class file contains Java bytecode.
Bytecode is like machine language, but it is
intended for the Java Virtual Machine not a specific
chip such as a Pentium or PowerPC chip
6. 12/20/2023 Fundamentals of Java Programming 6
More on How Java Works
To run a Java program the bytecode in a .class file
is fed to an interpreter which converts the byte code
to machine code for a specific chip (IA-32,
PowerPC)
Some people refer to the interpreter as "The Java
Virtual Machine" (JVM)
The interpreter is platform specific because it takes
the platform independent bytecode and produces
machine language instructions for a particular chip
So a Java program could be run an any type of
computer that has a JVM written for it.
– PC, Mac, Unix, Linux, BeaOS, Sparc
7. 12/20/2023 Fundamentals of Java Programming 7
A Picture is Worth…
The Interpreter's are sometimes referred to as the Java Virtual
Machines
The output of the
compiler is .class
file
8. 12/20/2023 Fundamentals of Java Programming 8
So What!
The platform independence of Java may be a huge
marketing tool, but is actually of little use to people
learning Object Oriented Programming and
Abstract Data Types
What is of use is the simplicity of the Java syntax
and programming concepts
Java is a "pure" Object Oriented Language
– encapsulation, inheritance, and polymorphism
– all code must be contained in a class
– no free functions (functions that do not belong to some
class) like C++, although someone who wants to write
messy Java code certainly can
– Is OO the best programming paradigm?
9. 12/20/2023 Fundamentals of Java Programming 9
HelloWorld.java
/**
* A simple program
*/
public class HelloWorld
{
public static void main(String[] args)
{
System.out.println("HELLO SCOE");
}
}
10. 12/20/2023 Fundamentals of Java Programming 10
More on Java Programs
All code part of some class
public class Foo
{ //start of class Foo
/*all code in here!*/
} // end of class Foo
The code for class Foo will be in a file
named Foo.java
– just a text file with the .java extension
– a class is a programmer defined data type
A complete program will normally consist of
many different classes and thus many
different files
11. 12/20/2023 Fundamentals of Java Programming 11
Error Types
Syntax error / Compile errors
– caught at compile time.
– compiler did not understand or compiler does not
allow
Runtime error
– something “Bad” happens at runtime. Java
breaks these into Errors and Exceptions
Logic Error
– program compiles and runs, but does not do
what you intended or want
12. 12/20/2023 Fundamentals of Java Programming 12
Question
What are the features of Java?
What is Platform Independence?
Who is the founder of Java?
14. 12/20/2023 Fundamentals of Java Programming 14
Basic Features
Data Types
– primitives
– classes / objects
Expressions and operators
Control Structures
Arrays
Methods
Programming for correctness
– pre and post conditions
– assertions
16. 12/20/2023 Fundamentals of Java Programming 16
Identifiers in Java
letters, digits, _, and $ (don't use $. Can confuse
the runtime system)
start with letter, _, or $
by convention:
1. start with a letter
2. variables and method names, lowercase with internal
words capitalized e.g. honkingBigVariableName
3. constants all caps with _ between internal words e.g.
ANOTHER_HONKING_BIG_INDENTIFIER
4. classes start with capital letter, internal words
capitalized, all other lowercase e.g
HonkingLongClassName
Why? To differentiate identifiers that refer to
classes from those that refer to variables
17. 12/20/2023 Fundamentals of Java Programming 17
Data Types
Primitive Data Types
– byte short int long float double boolean char
– stick with int for integers, double for real numbers
Classes and Objects
– pre defined or user defined data types consisting of constructors,
methods, and fields (constants and fields (variables) which may be
primitives or objects.)
//dataType identifier;
int x;
int y = 10;
int z, zz;
double a = 12.0;
boolean done = false, prime = true;
char mi = 'D';
18. 12/20/2023 Fundamentals of Java Programming 18
Java Primitive Data Types
Data
Type
Characteristics Range
byte 8 bit signed integer -128 to 127
short 16 bit signed integer -32768 to 32767
int 32 bit signed integer -2,147,483,648 to 2,147,483,647
long 64 bit signed integer -9,223,372,036,854,775,808 to-
9,223,372,036,854,775,807
float 32 bit floating point
number
+ 1.4E-45 to
+ 3.4028235E+38
double 64 bit floating point
number
+ 4.9E-324 to
+ 1.7976931348623157E+308
boolean true or false NA, note Java booleans cannot be
converted to or from other types
char 16 bit, Unicode Unicode character, u0000 to uFFFF
Can mix with integer types
19. 12/20/2023 Fundamentals of Java Programming 19
What are Classes and Objects?
Class is synonymous with data type
Object is like a variable
– The data type of the Object is some Class
– referred to as an instance of a Class
Classes contain:
– the implementation details of the data type
– and the interface for programmers who just want
to use the data type
Objects are complex variables
– usually multiple pieces of internal data
– various behaviors carried out via methods
20. 12/20/2023 Fundamentals of Java Programming 20
Creating and Using Objects
Declaration - DataType identifier
Rectangle r1;
Creation - new operator and specified
constructor
r1 = new Rectangle();
Rectangle r2 = new Rectangle();
Behavior - via the dot operator
r2.setSize(10, 20);
String s2 = r2.toString();
Refer to documentation for available
behaviors (methods)
21. 12/20/2023 Fundamentals of Java Programming 21
Built in Classes
Java has a large built
in library of classes
with lots of useful
methods
Ones you should
become familiar with
quickly
String
Math
Integer, Character,
Double
System
Arrays
Scanner
File
Object
Random
22. 12/20/2023 Fundamentals of Java Programming 22
import
import is a reserved word
packages and classes can be imported to
another class
does not actually import the code (unlike the
C++ include preprocessor command)
statement outside the class block
import java.util.ArrayList;
import java.awt.Rectangle;
public class Foo{
// code for class Foo
}
23. 12/20/2023 Fundamentals of Java Programming 23
More on import
can include a whole package
– import java.util.*;
or list a given class
– import java.util.Random;
instructs the compiler to look in the package for
types it can't find defined locally
the java.lang.* package is automatically
imported to all other classes.
Not required to import classes that are part of the
same project in Eclipse
24. 12/20/2023 Fundamentals of Java Programming 24
The String Class
String is a standard Java class
– a whole host of behaviors via methods
also special (because it used so much)
– String literals exist (no other class has literals)
String name = "Mike D.";
– String concatenation through the + operator
String firstName = "Mike";
String lastName = "Scott";
String wholeName = firstName + lastName;
– Any primitive or object on other side of + operator
from a String automatically converted to String
25. 12/20/2023 Fundamentals of Java Programming 25
Standard Output
To print to standard output use
System.out.print( expression ); // no newline
System.out.println( expression ); // newline
System.out.println( ); // just a newline
common idiom is to build up expression to
be printed out
System.out.println( "x is: " + x + " y is: " + y );
26. 12/20/2023 Fundamentals of Java Programming 26
Constants
Literal constants - "the way you specify values that
are not computed and recomputed, but remain,
well, constant for the life of a program."
– true, false, null, 'c', "C++", 12, -12, 12.12345
Named constants
– use the keyword final to specify a constant
– scope may be local to a method or to a class
By convention any numerical constant besides -1,
0, 1, or 2 requires a named constant
final int NUM_SECTIONS = 3;
28. 12/20/2023 Fundamentals of Java Programming 28
Question
What is Class?
What is Object?
How to create Object in Java?
29. 12/20/2023 Fundamentals of Java Programming 29
Operators
Basic Assignment: =
Arithmetic Operators: +, -, *, /, %(remainder)
– integer, floating point, and mixed arithmetic and
expressions
Assignment Operators: +=, -=, *=, /=, %=
increment and decrement operators: ++, --
– prefix and postfix.
– avoid use inside expressions.
int x = 3;
x++;
30. 12/20/2023 Fundamentals of Java Programming 30
Expressions
Expressions are evaluated based on the
precedence of operators
Java will automatically convert numerical
primitive data types but results are
sometimes surprising
– take care when mixing integer and floating point
numbers in expressions
The meaning of an operator is determined by
its operands
/
is it integer division or floating point division?
31. 12/20/2023 Fundamentals of Java Programming 31
Casting
Casting is the temporary conversion of a variable from its
original data type to some other data type.
– Like being cast for a part in a play or movie
With primitive data types if a cast is necessary from a less
inclusive data type to a more inclusive data type it is done
automatically.
int x = 5;
double a = 3.5;
double b = a * x + a / x;
double c = x / 2;
if a cast is necessary from a more inclusive to a less
inclusive data type the class must be done explicitly by the
programmer
– failure to do so results in a compile error.
double a = 3.5, b = 2.7;
int y = (int) a / (int) b;
y = (int)( a / b );
y = (int) a / b; //syntax error
32. 12/20/2023 Fundamentals of Java Programming 32
Primitive Casting
double
float
long
int
short,
char
byte
Outer ring is most
inclusive data type.
Inner ring is least
inclusive.
In expressions
variables and
sub expressions
of less inclusive
data types are
automatically cast
to more inclusive.
If trying to place
expression that is
more inclusive into
variable that is less
inclusive, explicit cast
must be performed.
From MORE to LESS
34. 12/20/2023 Fundamentals of Java Programming 34
Control Structures
linear flow of control
– statements executed in consecutive order
Decision making with if - else statements
if(boolean-expression)
statement;
if(boolean-expression)
{ statement1;
statement2;
statement3;
}
A single statement could be replaced by a
statement block, braces with 0 or more statements
inside
35. 12/20/2023 Fundamentals of Java Programming 35
Boolean Expressions
boolean expressions evaluate to true or false
Relational Operators: >, >=, <, <=, ==, !=
Logical Operators: &&, ||, !
– && and || cause short circuit evaluation
– if the first part of p && q is false then q is not
evaluated
– if the first part of p || q is true then q is not
evaluated
//example
if( x <= X_LIMIT && y <= Y_LIMIT)
//do something
36. 12/20/2023 Fundamentals of Java Programming 36
More Flow of Control
if-else:
if(boolean-expression)
statement1;
else
statement2;
multiway selection:
if(boolean-expression1)
statement1;
else if(boolean-expression2)
statement2;
else
statement3;
individual statements could be replaced by a statement
block, a set of braces with 0 or more statements
Java also has the switch statement, but not part of our
subset
37. 12/20/2023 Fundamentals of Java Programming 37
for Loops
for loops
for(init-expr;boolean-expr;incr-expr)
statement;
init-expr and incr-expr can be more zero or more
expressions or statements separated by commas
statement could be replaced by a statement block
execute
init-expr
evaluate
boolean-expr
false
skip to 1st statement after
body of loop
true
execute
body of loop
execute
incr-expr
38. 12/20/2023 Fundamentals of Java Programming 38
while loops
while loops
while(boolean-expression)
statement; //or statement block
do-while loop part of language
do
statement;
while(boolean-expression);
Again, could use a statement block
break, continue, and labeled breaks
– referred to in the Java tutorial as branching statements
– keywords to override normal loop logic
– use them judiciously (which means not much)
39. 12/20/2023 Fundamentals of Java Programming 39
Questions
What are the Basic Data Types in java?
What is the use of Loops?
Why we use Control Statement?
41. 12/20/2023 Fundamentals of Java Programming 41
Arrays in Java
"Should array indices start at 0 or 1? My compromise of 0.5 was rejected
without, I thought, proper consideration. "
– S. Kelly-Bootle
Java has built in arrays. a.k.a. native arrays
arrays hold elements of the same type
– primitive data types or classes
– space for array must be dynamically allocated with new operator.
(Size is any integer expression. Due to dynamic allocation does not
have to be constant.)
public void arrayExamples()
{ int[] intList = new int[10];
for(int i = 0; i < intList.length; i++)
{ assert 0 >= i && i < intList.length;
intList[i] = i * i * i;
}
intList[3] = intList[4] * intList[3];
}
42. 12/20/2023 Fundamentals of Java Programming 42
Array Details
all arrays must be dynamically allocated
arrays have a public, final field called length
– built in size field, no separate variable needed
– don't confuse length (capacity) with elements in
use
elements start with an index of zero, last index
is length - 1
trying to access a non existent element results
in an ArrayIndexOutOfBoundsException
(AIOBE)
43. 12/20/2023 Fundamentals of Java Programming 43
Array Initialization
Array variables are object variables
They hold the memory address of an array
object
The array must be dynamically allocated
All values in the array are initialized (0, 0.0,
char 0, false, or null)
Arrays may be initialized with an initializer
list:
int[] intList = {2, 3, 5, 7, 11, 13};
double[] dList = {12.12, 0.12, 45.3};
String[] sList = {"Olivia", "Kelly", "Isabelle"};
44. 12/20/2023 Fundamentals of Java Programming 44
Arrays of objects
A native array of objects is actually a native
array of object variables
– all object variables in Java are really what?
– Pointers!
public void objectArrayExamples()
{ Rectangle[] rectList = new Rectangle[10];
// How many Rectangle objects exist?
rectList[5].setSize(5,10);
//uh oh!
for(int i = 0; i < rectList.length; i++)
{ rectList[i] = new Rectangle();
}
rectList[3].setSize(100,200);
}
45. 12/20/2023 Fundamentals of Java Programming 45
Array Utilities
In the Arrays class, static methods
binarySearch, equals, fill, and sort
methods for arrays of all primitive types
(except boolean) and arrays of Objects
– overloaded versions of these methods for
various data types
In the System class there is an arraycopy
method to copy elements from a specified
part of one array to another
– can be used for arrays of primitives or arrays of
objects
46. 12/20/2023 Fundamentals of Java Programming 46
The arraycopy method
static voidarraycopy(Object src, int srcPos,
Object dest, int destPos, int length)
Copies an array from the specified source
array, beginning at the specified position, to
the specified position of the destination array.
int[] list = new int[10];
// code to fill list
// list needs to be resized
int[] temp = new int[list.length * 2];
System.arraycopy(list, 0, temp, 0,
list.length);
list = temp;
47. 12/20/2023 Fundamentals of Java Programming 47
2D Arrays in Java
Arrays with multiple dimensions may be
declared and used
int[][] mat = new int[3][4];
the number of pairs of square brackets
indicates the dimension of the array.
by convention, in a 2D array the first number
indicates the row and the second the column
Java multiple dimensional arrays are
handles differently than in many other
programming languages.
48. 12/20/2023 Fundamentals of Java Programming 48
Two Dimensional Arrays
0 1 2 3 column
0
1
2
row
0 0 0 0
0 0 0 0
0 0 0 0
This is our abstract picture of the 2D array and treating
it this way is fine.
mat[2][1] = 12;
49. 12/20/2023 Fundamentals of Java Programming 49
The Real Picture
mat
0
1
2
0 1 2 3
0 1 2 3
0 1 2 3
mat holds the memory address of an array with 3
elements. Each element holds the memory address
of an array of 4 ints
0 0 0 0
0 0 0 0
0 0 0 0
50. 12/20/2023 Fundamentals of Java Programming 50
Arrays of Multiple Dimension
because multiple dimensional arrays are
treated as arrays of arrays of
arrays……multiple dimensional arrays can
be ragged
– each row does not have to have the same
number of columns
– each row array has its own length field
int[][] raggedMat = new int[5][];
for(int i = 0; i < raggedMat.length; i++)
raggedMat[i] = new int[i + 1];
51. 12/20/2023 Fundamentals of Java Programming 51
Ragged Arrays
Ragged arrays are sometime useful, but
normally we deal with rectangular matrices
– each row has the same number of columns as
every other row
– use this a lot as precondition to methods that
work on matrices
working on matrices normally requires
nested loops
– why is this so hard?
52. 12/20/2023 Fundamentals of Java Programming 52
Enhanced for loop
New in Java 5.0
a.k.a. the for-each loop
useful short hand for accessing all elements in an
array (or other types of structures) if no need to
alter values
alternative for iterating through a set of values
for(Type loop-variable : set-expression)
statement
logic error (not a syntax error) if try to modify an
element in array via enhanced for loop
53. 12/20/2023 Fundamentals of Java Programming 53
Enhanced for loop
public static int sumListEnhanced(int[] list)
{ int total = 0;
for(int val : list)
{ total += val;
System.out.println( val );
}
return total;
}
public static int sumListOld(int[] list)
{ int total = 0;
for(int i = 0; i < list.length; i++)
{ total += list[i];
System.out.println( list[i] );
}
return total;
}
55. 12/20/2023 Fundamentals of Java Programming 55
Methods
methods are analogous to procedures and
functions in other languages
– local variables, parameters, instance variables
– must be comfortable with variable scope: where is a
variable defined?
methods are the means by which objects are
manipulated (objects state is changed) - much
more on this later
method header consists of
– access modifier(public, package, protected, private)
– static keyword (optional, class method)
– return type (void or any data type, primitive or class)
– method name
– parameter signature
56. 12/20/2023 Fundamentals of Java Programming 56
More on Methods
local variables can be declared within methods.
– Their scope is from the point of declaration until the
end of the methods, unless declared inside a
smaller block like a loop
methods contain statements
methods can call other methods
– in the same class: foo();
– methods to perform an operation on an object that
is in scope within the method: obj.foo();
– static methods in other classes:
double x = Math.sqrt(1000);
57. 12/20/2023 Fundamentals of Java Programming 57
static methods
the main method is where a stand alone Java program
normally begins execution
common compile error, trying to call a non static method
from a static one
public class StaticExample
{ public static void main(String[] args)
{ //starting point of execution
System.out.println("In main method");
method1();
method2(); //compile error;
}
public static void method1()
{ System.out.println( "method 1"); }
public void method2()
{ System.out.println( "method 2"); }
}
58. 12/20/2023 Fundamentals of Java Programming 58
Method Overloading and Return
a class may have multiple methods with the same
name as long as the parameter signature is unique
– may not overload on return type
methods in different classes may have same name
and signature
– this is a type of polymorphism, not method overloading
if a method has a return value other than void it
must have a return statement with a variable or
expression of the proper type
multiple return statements allowed, the first one
encountered is executed and method ends
– style considerations
59. 12/20/2023 Fundamentals of Java Programming 59
Method Parameters
a method may have any number of
parameters
each parameter listed separately
no VAR (Pascal), &, or const & (C++)
final can be applied, but special meaning
all parameters are pass by value
Implications of pass by value???
60. 12/20/2023 Fundamentals of Java Programming 60
Value Parameters vs.
Reference Parameters
A value parameter makes a copy of the
argument it is sent.
– Changes to parameter do not affect the
argument.
A reference parameter is just another name
for the argument it is sent.
– changes to the parameter are really changes to
the argument and thus are permanent
61. 12/20/2023 Fundamentals of Java Programming 61
Value vs. Reference
// value
void add10(int x)
{ x += 10; }
void calls()
{ int y = 12;
add10(y);
// y = ?
}
// C++, reference
void add10(int& x)
{ x += 10; }
void calls()
{ int y = 12;
add10(y);
// y = ?
}
12
y
12
x
12
y x
62. 12/20/2023 Fundamentals of Java Programming 62
More Features
Inheritance
Polymorphism
Data Abstraction
Dynamic Binding