The document provides an overview of the history and features of Java, highlighting its simplicity, portability, and rich library support. It discusses programming concepts such as variable rules, numeric data types, constants, and object-oriented programming principles, emphasizing the importance of naming conventions and best practices. Additionally, it briefly introduces Java IDEs and string comparison methods.

1. Learn JAVA at AMC Square
Learning

2. Java History
• 1991: used in consumer devices
• 1994: used in browsers
• programmers embraced because:
• simpler than C++.
• rich library.
• portable programs.
• micro edition and enterprise edition provide support for wide range
of apps, from cell phones to large Internet servers.
• safe and secure.
• Java virtual machine (JVM) catches many mistakes, makes it easier to
use.

3. Learning Java
• Very similar to C++in most respects
• All programs are class definitions
• All objects are created dynamically (using new)
• Extensive library – you must read Java documentation!

4. Variables
Rules for identifiers:
• Can include letters, digits, _, $, can’t start with digits
• Spaces and other characters not permitted
• Cannot use reserved words (e.g., public)
• Case sensitive
Conventions you must follow for CSCI306:
• variable and method names should start with lower case, may
include uppercase within (camel case). e.g., luckyNumber
• Class names should begin with uppercase
• Constants should be in ALL_CAPS
• Variable and class names should be meaningful!!

5. Assignment and Initialization
• As in C++, variables have a type
• Unlike C++, variables MUST be assigned a value before being used
int example;
System.out.println(example); // ERROR
if (tot = 5) // Compiler ERROR – must be boolean

6. Numeric Data Types
• Integer values can be represented exactly, but numeric
operations may result in overflow
• Floating point values may not be exact, so rounding errors
may occur (shouldn’t use == with floating point values, use
tolerance)
• double is therefore not appropriate for financial calculations
• java.math has “BigInt” and “BigDec” classes which are slow
but have better size/precision. Must use add, subtract and
multiply (no operator overloading in Java)

7. Constant values
• preceded by keyword final (vs const in C++)
• naming convention is all uppercase
• e.g.,
final double QUARTER_VALUE = 0.25;
• if used in a class, often make public (since can’t change anyway) and often
use keyword static, meaning constant belongs to the class:
public static final double DIME_VALUE =0.1;
• Math class has some useful constants, e.g.,
double circumference = Math.PI * diameter;
(vs Math::PI in C++)

8. Numeric Operations
•It has a number of static functions like sqrt, pow, sin, cos, exp,
log, round, max, min, etc…..
• put space after every Java keyword, but not between a method
name and parentheses
• put space around all binary operators
• factor out common code
•Remember that you may need to round floating point values
double f = 4.35;
int n = (int) (100 * f);
System.out.println(n); // prints 434!
Replace with:
int n = (int) Math.Round(100 * f);

9. Loops in Java
• while loops – same as C++
• same common errors: infinite loops, off-by-one
• do loops – same as C++
• for loops – same as C++ (but with another useful syntax for
collections)
• same common errors: forget semicolon if need empty body, or
include semicolon on for statement
• Quality tip: for loops are best for counting loops. Use a while loop
for other types
• nested Loops – same as in C++
• Quality tip: don’t use != to test the end of a range, better to use <, <=
etc.
• sentinel loops – same as in C++

10. Class
In object-oriented programming, a class is an extensible
program-code-template for creating objects, providing initial
values for member variables and implementations of member
functions, methods. The class name is used as the name for
the class and as the type of objects generated by the type, and
these distinct concepts are easily conflated.

11. Objects
Objects are key to understanding object-
oriented technology. Look around and you'll find many
examples of real-world objects.
For example : Dog, television set, bicycle.
They all have state and behavior. these have state (name,
color..etc.) and behavior (the way they works/ behave).
Identifying the state and behavior for real-world objects is a
great way to begin thinking in terms of object-oriented
programming.

12. Java IDE
A Java IDE (Integrated Development
Environment) is a software application which
enables users to more easily write and debug
Java programs. Many IDEs provide features
like syntax highlighting and code completion,
which help the user to code more easily.
NetBeans…..etc. are called java IDEs
As we know which are more popular, like….
Eclipse

13. Comparing Strings
• To compare contents of strings, use equals:
if (string1.equals(string2)) . . .
• May prefer to ignore case:
if (string1.equalsIgnoreCase(string2)) . . .
• Can use compareTo to find out the relationship (<0 if first is
less, ==0 if same, >0 if first is greater):
if (string1.compareTo(string2)) < 0) . . .

14. Thank you