Download Data Structures and Algorithms - M Pervez Akhtar

By Mr. Muhammad Pervez Akhtar
[email protected]
http://pervez.farooka.com
 The
general environment
 The first program

Comments, Main, Terminal Output
 Primitive

Primitive types, Constants, Declaration and
Initialization, Terminal Input and Output
 Basics

types
Operators
Assignment Operators, Binary Arithmetic
Operators, Unary Operators, Type Conversion
Operators
 Conditional

Statements
Relational and equality operators, Logical
operators, The if statement, The while statement,
The for statement, The do statement, break and
continue, The switch statement, The conditional
operator
 Methods


Overloading of method names
Storage classes
Java Source code resides in files whose names end
with the .java suffix
 The local compiler, javac, compiles the program and
generates .class files, which contain bytecode
 Java bytecodes represent the portable intermediate
language that is interpreted by running the Java
interpreter, java.
 The interpreter is also known as the Virtual Machine
 Java programs, input can come from one of many
places:


Standard input, Command Line Arguments, A File, GUI
Component
 Save
program as FirstProgram.java
 Compile program as javac FirstProgram.java
 Run program as javac FirstProgram
 Four things to note in program

Comments, class, main method, standard output
 Comments
are non-compiled and nonexecutable code
 Three types of comments



// : single line comment, inherited from C
/*…*/: multi line comments inherited from c
/**…*/: information for javadoc utility to generate
documentation form comments
 Why



Comments are needed?
Make code easier for humans to read
Helps programmers to modify the program
Commented program is a good sign of programmer
 Java
program consists of interacting classes
which contain methods and data elements
 Methods can be invoked using object of its
class
 Static method can be invoked without object
of its class
 Public static void main(String args[]) is
special method with void return type,
command line argument, public access
modifier and is static
 It is the method that executes first of all
 System.out.println:
is the primary output
mechanism in java
 Also called standard output (output on
console)
 System.out.print: is another way of output
 println vs print


println shifts control to start of next line after
output
but print does not shifts control to next line
 Can
output integer, floating point, string, or
some other type

Integer constants can be represented in either
decimal, octal, or hexadecimal notation
Octal notation is indicated by a leading 0; hexadecimal is
indicated by a leading 0x or 0X
 Equivalent ways of representing the integer 37:



::Decimal, Octal and Hexa
Character constant is enclosed with a pair of single
quotation marks, as in 'a‘


37,045,0x25
Internally, this character sequence is interpreted as a
small number
String constant consists of a sequence of characters
enclosed within double quotation marks, as in
"Hello"
 Escape
sequence is a constant but with
special meanings
 It starts with a ‘\’ backslash followed by a
character to print
 Followings are commonly used:
 ‘\n’
New line character
 ‘\\’
Backslash character
 ‘\’’
Single quotation mark
 ‘\”’
Double quotation mark
A
primitive type, is declared by providing its
type, its name, and optionally its initial value
 Type should be primitive type (int, float etc)
 The name must be an identifier, that consists of:




Any combination of letters, digits, and the underscore character but it not start with a digit
Reserved words are not allowed
Not reuse identifier names that are already visibly
used
Are case sensitive, age or Age are different
Basic formatted terminal I/O is accomplished by
nextLine and println
 The standard input stream is System.in
 The standard output stream is System.out
 Formatted I/O uses the String type

 + combines two Strings
 If one of the argument is not a String, a temporary
String is created for it if it is a primitive type
 For input, we associate a Scanner object with
System.in.
 Scanner has different methods for different
primitive types
 Operators
are symbols to perform an operation
 Operators are used to form expressions
 Expression is combination of variables,
constants and operators
 Following are the types of operators




Assignment Operators =, +=, -=, *=, /=
Binary Arithmetic Operators +, -, *, /, %
Unary Operators ++, --, - ::prefix or postfix use
Type Conversion Operators

Generate a temporary entity of a new type
 Statements
that affect the flow of control
 Relational and Equality operators

<, <=, >, >=, ==, !=
 Logical




Operators
AND, OR, NOT or conjunction, disjunction and
negation respectively
&&, ||, ! Is another representation
! Has highest precedence and && has higher
precedence than ||
&& and || called short-circuit operators
 The
IF, IF THAN ELSE statement
 Two
common mistakes
 Loops
the While, For, and Do statements
 Break

and Continue statements
Break statement terminate execution in the
middle of a repeated statements (loop)
 Continue
Statement
Give up on the current iteration of a
loop and go on to the next iteration
 Switch

Suitable when multiple branches against one
Condition
 The


Statement
conditional operator
a shorthand for simple if-else statements
testExpr ? yesExpr : noExpr
Known as a function or procedure :: main()
 A method header consists of a name, a (possibly
empty) list of parameters, and a return type
 The actual code to implement the method,
sometimes called the method body
 A method declaration consists of a header plus
the body
 Overloading of method


Several methods may have the same name and be
declared in the same class scope as long as their
signatures(that is, their parameter list types) differ.
 Local


Variables:
Entities that are declared inside the body of a
method are local variables
Can be accessed by name only within the method
body
 Global


A variable declared outside the body of a method
is global to the class
if the word static is used, is similar to global
variables in other languages
 Static

Variables
Final Variable
If both static and final are used, they are global
symbolic constants