Unit I Advanced Java Programming Course

Dr. S.SHAIK PARVEEN
Department of Computer Science

CLASS DETAILS
 Academic Year 2021-2022
 I M.Sc.(CS)
 II Semester
 Batch 2020-2022
 Course Coordinator: Dr. S.SHAIK PARVEEN

 Course Name: Advanced Java
Programming
 Course Code : 20PCSC21
 Semester : II Part III : Core
COURSE INFORMATION

COURSE PREREQUISITES
 basic understanding of the Java language
 a basic understanding of software
development
 a basic understanding of the software
development life cycle
4
Course Co-requisites
 Good understanding of programming and
OOPs concepts.

COURSE OBJECTIVES:
 To learn how to use Core Java Technologies.
 To implement OOP Concept.
 To get knowledge in Classes, Fundamentals,
Methods, Constructors and Garbage
 To analyze the current Thread and Synchronization
 To cover Applet, AWT Controls, Swing and Java
Beans.

UNIT I
JAVA - GENERAL
 Java is:
 platform independent programming language
 similar to C++ in syntax
 similar to Smalltalk in mental paradigm
 Pros: also ubiquitous to net
 Cons: interpreted, and still under development
(moving target)

JAVA - GENERAL
 Java has some interesting features:
 automatic type checking,
 automatic garbage collection,
 simplifies pointers; no directly accessible pointer to
memory,
 simplified network access,
 multi-threading!

Compile-time Environment
Compile-time Environment
Java
Bytecodes
move locally
or through
network
Java
Source
(.java)
Java
Compiler
Java
Bytecode
(.class )
Java
Interpreter
Just in
Time
Compiler
Runtime System
Class
Loader
Bytecode
Verifier
Java
Class
Libraries
Operating System
Hardware
Java
Virtual
machine
HOW IT WORKS…!

HOW IT WORKS…!
 Java is independent only for one reason:
 Only depends on the Java Virtual Machine
(JVM),
 code is compiled to bytecode, which is
interpreted by the resident JVM,
 JIT (just in time) compilers attempt to
increase speed.

JAVA - SECURITY
 Pointer denial - reduces chances of virulent
programs corrupting host,
 Applets even more restricted -
 May not
 run local executables,
 Read or write to local file system,
 Communicate with any server other than the originating server.

OBJECT-ORIENTED
 Java supports OOD
 Polymorphism
 Inheritance
 Encapsulation
 Java programs contain nothing but definitions and
instantiations of classes
 Everything is encapsulated in a class!

JAVA ADVANTAGES
 Portable - Write Once, Run Anywhere
 Security has been well thought through
 Robust memory management
 Designed for network programming
 Multi-threaded (multiple simultaneous tasks)
 Dynamic & extensible (loads of libraries)
 Classes stored in separate files
 Loaded only when needed

PRIMITIVE TYPES AND VARIABLES
 boolean, char, byte, short, int, long, float, double etc.
 These basic (or primitive) types are the only types
that are not objects (due to performance issues).
 This means that you don’t use the new operator to
create a primitive variable.
 Declaring primitive variables:
float initVal;
int retVal, index = 2;
double gamma = 1.2, brightness
boolean valueOk = false;

INITIALISATION
 If no value is assigned prior to use, then the
compiler will give an error
 Java sets primitive variables to zero or false
in the case of a boolean variable
 All object references are initially set to null
 An array of anything is an object
 Set to null on declaration
 Elements to zero false or null on creation

DECLARATIONS
int index = 1.2; // compiler error
boolean retOk = 1; // compiler error
double fiveFourths = 5 / 4; // no error!
float ratio = 5.8f; // correct
double fiveFourths = 5.0 / 4.0; // correct
 1.2f is a float value accurate to 7 decimal places.
 1.2 is a double value accurate to 15 decimal places.

ASSIGNMENT
 All Java assignments are right associative
int a = 1, b = 2, c = 5
a = b = c
System.out.print(
“a= “ + a + “b= “ + b + “c= “ + c)
 What is the value of a, b & c
 Done right to left: a = (b = c);

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

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

BASIC MATHEMATICAL OPERATORS
 * / % + - are the mathematical operators
 * / % have a higher precedence than + or -
double myVal = a + b % d – c * d / b;
 Is the same as:
double myVal = (a + (b % d)) –
((c * d) / b);

STATEMENTS & BLOCKS
 A simple statement is a command terminated by
a semi-colon:
name = “Fred”;
 A block is a compound statement enclosed in
curly brackets:
{
name1 = “Fred”; name2 = “Bill”;
}
 Blocks may contain other blocks

FLOW OF CONTROL
 Java executes one statement after the other
in the order they are written
 Many Java statements are flow control
statements:
Alternation: if, if else, switch
Looping: for, while, do while
Escapes: break, continue, return

IF – THE CONDITIONAL STATEMENT
 The if statement evaluates an expression and if that
evaluation is true then the specified action is taken
if ( x < 10 ) x = 10;
 If the value of x is less than 10, make x equal to 10
 It could have been written:
if ( x < 10 )
x = 10;
 Or, alternatively:
if ( x < 10 ) { x = 10; }

RELATIONAL OPERATORS
== Equal (careful)
!= Not equal
>= Greater than or equal
<= Less than or equal
> Greater than
< Less than

IF… ELSE
 The if … else statement evaluates an expression
and performs one action if that evaluation is true or
a different action if it is false.
if (x != oldx) {
System.out.print(“x was changed”);
}
else {
System.out.print(“x is unchanged”);
}

NESTED IF … ELSE
if ( myVal > 100 ) {
if ( remainderOn == true) {
myVal = mVal % 100;
}
else {
myVal = myVal / 100.0;
}
}
else
{
System.out.print(“myVal is in range”);
}

ELSE IF
 Useful for choosing between alternatives:
if ( n == 1 ) {
// execute code block #1
}
else if ( j == 2 ) {
}
else {
// if all previous tests have failed, execute
code block #3
}

A WARNING…
WRONG!
if( i == j )
if ( j == k )
System.out.print
(
“i equals
k”);
else
System.out.print(
“i is not equal
to j”);
CORRECT!
if( i == j ) {
if ( j == k )
System.out.print(
“i equals k”);
}
else
System.out.print(“
i is not equal to
j”); //
Correct!

THE SWITCH STATEMENT
switch ( n ) {
case 1:
break;
case 2:
break;
default:
// if all previous tests fail then
//execute code block #4
break;
}

THE FOR LOOP
 Loop n times
for ( i = 0; i < n; n++ ) {
// this code body will execute n times
// ifrom 0 to n-1
}
 Nested for:
for ( j = 0; j < 10; j++ ) {
for ( i = 0; i < 20; i++ ){
// this code body will execute 200 times
}
}

WHILE LOOPS
while(response == 1) {
System.out.print( “ID =” + userID[n]);
n++;
response = readInt( “Enter “);
}
What is the minimum number of times the loop
is executed?
What is the maximum number of times?

DO {… } WHILE LOOPS
do {
System.out.print( “ID =” + userID[n] );
n++;
response = readInt( “Enter ” );
}while (response == 1);
What is the minimum number of times the loop
is executed?
What is the maximum number of times?

BREAK
 A break statement causes an exit from the
innermost containing while, do, for or
switch statement.
for ( int i = 0; i < maxID, i++ ) {
if ( userID[i] == targetID ) {
index = i;
break;
}
} // program jumps here after break

CONTINUE
 Can only be used with while, do or for.
 The continue statement causes the innermost loop
to start the next iteration immediately
for ( int i = 0; i < maxID; i++ ) {
if ( userID[i] != -1 ) continue;
System.out.print( “UserID ” + i + “ :” +
userID);
}

ARRAYS
 Am array is a list of similar things
 An array has a fixed:
 name
 type
 length
 These must be declared when the array is created.
 Arrays sizes cannot be changed during the
execution of the code

myArray has room for 8 elements
 the elements are accessed by their index
 in Java, array indices start at 0
3 6 3 1 6 3 4 1
myArray =
0 1 2 3 4 5 6 7

DECLARING ARRAYS
int myArray[];
declares myArray to be an array of integers
myArray = new int[8];
sets up 8 integer-sized spaces in memory, labelled
myArray[0] to myArray[7]
int myArray[] = new int[8];
combines the two statements in one line

ASSIGNING VALUES
 refer to the array elements by index to store values
in them.
myArray[0] = 3;
myArray[1] = 6;
myArray[2] = 3; ...
 can create and initialise in one step:
int myArray[] = {3, 6, 3, 1, 6, 3, 4, 1};

ITERATING THROUGH ARRAYS
 for loops are useful when dealing with arrays:
for (int i = 0; i < myArray.length; i++) {
myArray[i] = getsomevalue();
}

ARRAYS OF OBJECTS
 So far we have looked at an array of primitive
types.
 integers
 could also use doubles, floats, characters…
 Often want to have an array of objects
 Students, Books, Loans ……
 Need to follow 3 steps.

DECLARING THE ARRAY
1. Declare the array
private Student studentList[];
 this declares studentList
2 .Create the array
studentList = new Student[10];
 this sets up 10 spaces in memory that can
hold references to Student objects
3. Create Student objects and add them to the
array: studentList[0] = new
Student("Cathy", "Computing");

Unit I Advanced Java Programming Course

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