Java Programming concept

What is Java?
• Java is a purely an Object Oriented programming language
• Java began life as the programming language called ‘OAK’
• OAK was developed in 1991 by the programmers of Sun
Microsystem, Now owned by Oracle Inc.
• Oak developer team wanted a new way of computing, so
they decided to make programming language to run in
different kinds of computers, consumer devices and OAK
got the new name called ‘Java’
• The goal of java is “Write Once; run anywhere”. It is
platform independent language
• Java is inspired by C, C++ syntax.

Applications of Java
• Embedded Systems such as consumer devices
• Personal Computers
• Distributed Systems
• World Wide Web(Eg. Applet, JSP etc)
• Smart Phones, Mobiles

Java Editions
• Java 2 Standard Edition(J2SE)- Used for
standard desktop application development
• Java 2 Enterprise Edition(J2EE)- Used for
developing Web or Distributed applications
• Java 2 Micro Edition(J2ME) – Used for
application development for most of the
featured mobiles phones i.e Nokia Series 40,
eg. Nokia 2700.

JAVA ENVIRONMENT
• Java is both compiled and interpreted
C Code
Machine Code(CPU Specific)
Compiled
JAVA Code
Bytecode(CPU independent)
Executed By CPU,
Executed By Java Virtual
Machine,
Compiled
Interpreted

Java Virtual Machine
• JVM is a software program which can execute
the byte codes. It runs on existing OS.It is a
type of virtual machine.

Byte code
• It is fully optimized set of instructions designed to
be executed by JVM(Java Virtual Machine)
• Translating Java Program into byte code helps run
program in wide variety of environment s
because only task is to make JVM for that
particular platform
• Byte code is interpreted by JVM.
• It is secure because execution of Java program is
always under control of JVM
• In computer, bytecode is stored in a Class file. Eg.
Test.class

Features of Java
• Simple and powerful:
– It is simple to understand by professional programmers
– Every one with the knowledge of programming and Object oriented
programming concept feels it is simple
• Secure
– Java programs are confined within Java execution environment or
JVM, Java programs and Applets(Web GUI objects) can be downloaded
without fear of virus
• Portable
– Java uses byte code concept which is not executed by CPU but Java
virtual machine so we can use single code for multiple platforms
• Object Oriented
– Java uses realistic approach of OOP. Every thing other than simple data
types such as int, float etc are used as objects.

Features of Java
• Robust:
– Java programs are reliable from memory management view
– Java forces programmers to find mistakes in early stage of
development
– Java has automatic Garbage Collection. So users need not to be worry
about memory management problems which is big disadvantage of C
where users need to allocate and de-allocate memory manually.
– Garbage Collection is the feature of JVM where memory is allocated
for object when uses and if objects are not used, they are cleared
from memory
• Multithreaded
– Thread is a particular part of a program. Java enables performing
multiple tasks within a program simultaneously.
– E.g. Antivirus can do two repetitive tasks together. We can update
antivirus while virus scan is running
• Architecture-Neutral
– Once java program is written, it can be executed in any environment.

Features of Java
• Interpreted and High Performance:
– Java programs run comparatively faster than other
interpreted language like BASIC
– It is designed to run in low power CPU. So Java is the first
choice for Mobile Programming.
• Distributed
– Java programs can run over TCP/IP protocols. We can
design programs which can call the methods of Remote
program. For this, java provides RMI(Remote Method
Invocation)
• Dynamic
– Java allows accessing objects dynamically in run time.
Small fragment of byte code can be updated dynamically in
the run-time.

Object Oriented Programming Concept
•Every Object has attributes(state) and
behavior, for Tata-Nano Object
Particular TATA-Nano is a
real world object
States or attributes Behaviour
Wheels Gear up
Model Run
Horse Power Gear down
Seats Brake
• For every Computer Object,
attributes(state) are called data or
behavior is called Method
Data(Variables) Methods(Functions)
totWheels gearUp()
modelNo run()
horsePower gearDown()
totalSeats brakeDown()
In a Racing Game(Ferrari)

Computer OBJECT
Definition
An Object is a software
bundle of related
state(fields or data) and
behavior(Methods or
functions). Software
objects are often used to
model real world objects
that we find in everyday
life. E.g. Button, Car, Cat
etc
Task: Make a list of objects you see in your everyday life and make a list of their
states and behavior.

What is CLASS
CAR ANIMAL
Tata-Nano Ferrari Cow Tiger
Tata-nano and Ferrari fall under CAR class, Cow and Tiger fall
under Animal class
In object-oriented terms, we say that our bike(eg. Pulsar) is an instance of the class of
objects known as motorbike. A class is the blueprint(outline) from which individual objects
are created.

What is Abstraction
Abstraction is one of the fundamental principle of OOP
which helps to reduce the complexity. It helps to separate
methods and data that change frequently. In makes
system flexible.
You got a new mobile. You start using it without knowing the complexity of it’s internal
structure. While using Mobile, we do not need to know about its internal parts. The
frequently changeable features like Battery, cover, sim card are accessible. Other parts are
hidden. This reduces complexity.

Encapsulation
Encapsulation is the mechanism that binds code and data
together and keeps both safe from outside misuse. It is the
protective wall to prevent code inside class being
randomly accessed.
* Note : abstraction and encapsulation seem to be similar but abstraction uses interface
and encapsulation uses access modifiers(private, public,protected) to hide data. These
will be discussed later

What is Inheritance
Vehicle
Bike
CBZ Discover
Car
Santro
Maruti-
SX4
Object
Controls
Button Textbox
Forms
MDI
parent
Dialog
•Different kinds of objects often have a certain amount in common with each other
•Bike, Car class inherit from Vehicle class. CBZ, Discover inherit from Bike Class
•The possible object for here becomes particular CBZ bike with particular engine number.
•Here Vehicle is Super Class for derived class Bike, and Bike is called Base or derived class
•In OOP, Inheritance is the way to reuse the code of existing class. Here one object acquires
properties of another object.
Objects: Button save , exit;

Polymorphism
•Polymorphism(“ Many Forms”) is the process of making methods in OOP to perform
multiple tasks. eg;: we can make a function called ADD() to calculate the sum of two
numbers or two Strings with a single name. Making such methods is also called
Overloading

Starting Java
To work with java, We need following:
•Latest Java Development Kit(www.oracle.com) . It also
JRE(java runtime environment)
•Any text editors like Notepad, Notepad++
•IDE(Integrated Development Environment) like
Netbean or Eclipse for easier development

Installing and configuring
•Install JDK
•Define following environment
variables
•Goto run
•Type sysdm.cpl
•Goto Advanced tab
•Click environment variable
button

Installing and configuring
•Path: ;C:Program Files (x86)Javajdk1.6.0bin
•CLASSPATH: D:Java
•JAVA_HOME: C:Program Files (x86)Javajdk1.6.0bin
Path: defining path helps to access java commands directly from Command
Prompt(cmd)
CLASSPATH: the location where compiled classes are loaded, java searches classes
here
JAVA_HOME:It is the path of directory where Java.exe can be found

First Java Program
//class name is First so save file as First.java
class First{
public static void main(String args[]) {
System.out.println(“First Program”);
}
}
•Save file as First.java
• compile:
•D:/java>javac First.java
•Run
•D:/java>java First
First Program

First Java Program
class First {
It defines the name of the class
// this is single line comment
/* thi is multi line
Comment
*/
public static void main(String args[]){
•public : It is public access modifier which can be called from outside.
•Static : this keyword tells that to call main() function, instance of First is not required.
Every static data members can be directly accessed without creating object of class.
•void refers an empty data type so this function does not return any value
•main()- the function that is called automatically when application is launched
•args[]-these are number of values which can be passed into program.
•For example:
•C:/>format c: enter
•Here c: is an argument
Enter

Coding Conventions
•make all constants are written in UPPERCASE.
Eg.MAX_HOURS,FILL_COLOR etc
•Eg: static final MAX_SPEED=100;
• write all statements and other keywords in lowercase eg
import,if,for,while
•Name of the class is CamelCased. Eg MyFirstClass. If single word
is used then : class First { }.
•Objects, variables and function names are written in mixedCase.
For example:
•Button butSave=new Button();
•public int findSum() {
•Int firstNum,secondNum etc
•Always initialize values of the variables before use.

Second Java Program
//class name is First so save file as SecondJava.java
class SecondJava{
int age=10;
System.out.println(“I am ”+age+” years old.
After 10 years, I will be “+(age+10)+” years old”);
}
}
•Save file as SecondJava.java
• compile:
•D:/java>javac SecondJava.java
•Run
•D:/java>java SecondJava
I am 10 years old. After 10 years, I will be 20 years old

Data Types
Java is called Strongly Typed or strict typed language because
every identifier(variable or constant) has data type and these all
needs to be strictly defined first with type and used later. It is
similar to C, C++. But java is more strict. You can not assign
floating point value to integer but in java you can not. Java
compiler performs strong-type checking during compilation.
int a=2.2; is wrong in java but correct in c,c++

Simple Data Types
These are also called primitive data type.
Integers: integer data type holds integer value which is signed. Java does
not support positive only values like C.
byte 1byte -128 to 127
short 2 bytes -32768 to 32767
 int 4 bytes -(231 ) to (231)-1
long 8 bytes(64bit) -(263) to (263)-1
Floating-Point Types hold real numbers and used with fractional values:
float 32bits 1.4e-45 to 3.4e038
double 64bits 4.9e-324 to 1.8e308
Characters: Java char data type uses 16 bit space where c, c++ char takes 8
bit. The reason is java also supports Unicode representation. Characters are
treated numeric values as we can do calculations also, In java char is used

Simple Data Types
Boolean: Boolean holds logical values such as true or false. It
occupies 1 bit storage
class CharTest{
char a='A';
char b=66;
System.out.printf("a is %c and b is %c ",a,b);
++b;
System.out.println(" and after increment, b is "+b);
}
}
Output is : a is A and b is B and after increment, b is C

Wrapper Class(Reference Types)
There are some situations where data types are required to
be true objects.eg. If we want to derive data type. For this
purpose java provides wrapper classes where primitive data
types are written as object, here first letter is capitalized.
Eg. Integer, String, Character etc.
public class First {
int a=10;
Integer obj=new Integer(15);
System.out.println("premitive is "+a+" Wrapper is
"+obj.intValue());
}
}

Literals
Literals are the values assigned to any variable.
•Eg. Int a=5; here 5 is integer literal.
•String literals are double quoted
String name=“Suman”
•Boolean literal uses true or false keyword
boolean a=true;
•A character is single quoted
char choice=‘Y’;

Escape Sequence
Escape characters are written with . These are used to
represent control characters
Escape Description
n New line
t Tab
’ Single quote
” Double quote
f Form feed
b Backspace
ddd Octal
uxxx unicode

Example
public class Escape{
String quote="Programming is Fun";
System.out.println("Many people say ""+quote+""");
}
}
Output is : Many people say “Programming is Fun”

Variables
Variable is an identifier which holds certain value that can be
changed. A variable has type, scope and lifetime. Variable
name can start with $ or an alphabet and can be followed by
underscore. It can not contain whitespace.
•Declaring variable
<type> <var_name>=[<value>]
Eg.
Int a=5; //declared and initialized
Int x,y,z; //declared only
Int m,n=6; //mixed declaration and initialization
Int t; // declared and later initialized
t=9;

Dynamic initialization
What is dynamic initialization? Give an example. (QB)
Dynamic initialization is the process of assigning value to
a variable dynamically during runtime. We can not perform
dynamic initialization to the variables declared with final
keyword.
public class Init{
int a=10; // this is static initialization
int b=a*10; //this is dynamic initialization
System.out.println(“a is “+a+” and b is “+b);
}
}
Output is : a is 10 and b is 100

Variable scope and lifetime
Scope refers variable accessibility and lifetime refers to its’
existence. Curly brace defines the scope.
{
int a;
}
// a can not be accessed from here

Variable scope and lifetime
Nested scope.
class test{
int a;
class inner{
int a;
// wrong duplicate definition. Variable can be accessed
from inner scope.
}
}
Where program exit from scope, variable is destroyed

Type conversion and Casting
Type casting is the process of converting values from one type to
another type.
•Automatic conversion(implicit)
•Automatic conversion takes place if two types are
compatible(ie. Int,float,byte,short,long etc)
•If destination is larger than source.
If above conditions are met, Widening Conversion takes
place
•Casting incompatible types(explicit)
Casting between incompatible types, we need to use cast
expression,
(target-type) value;
Eg. Convert int to byte

Automatic type promotion
Consider a situation
byte a=30;
byte b=20;
int c=b*c;
While converting using expression b*c may become more than
255. so while using short and byte to any expression, these are
automatically promoted to int.
Another example
byte a=20;
b=a*2; //wrong can not assign int to byte
// this is correct way because int is converted to byte
b=(byte)(a*2);

Type conversion and Casting
int a;
a=258;
byte b;
b=(byte) a; // a is integer and casted to byte
Note: here b is byte which holds smaller values than int. byte
can hold 8 bits. So maximum values are 28=256.
When we assign 258 to byte, Narrowing Conversion takes
place. If target smaller than only remainder will be assigned.
So value of b becomes 258 % 256=2

Example
public class cast {
int a; // this is static initialization
byte b;
a=258;
b=(byte) a;
System.out.println(b); //2 will be printed
float f=15.55f;
int c=(int) f;
System.out.println(c); // 15 will be printed
double e=1554554.4582;
float g=(float) e;
System.out.println(g); // 1554554.5 will be printed because it can take upto 8
digits
}
}

Type promotion rules
When an expression contains many types. Other types are
promoted to bigger one.
•In an expression byte and short are automatically promoted
to int
•If one operand is long, entire expression is converted to long
•If any operand is float, entire expression is converted to
float
•If any operand is double, entire expression is converted to
double

Example of promotion
class AutoPromote{
byte a=50;
short s=1000;
int i=10550;
float f=10.5f;
double d=1.12546;
double result=(a*s)+(i/f)+(d*i);
System.out.println(result);
}
}
Output:
62878.36471875
Here,
•Expression contains largest type double, so result type must be double
•a*s becomes int so a*s=50000
•In i/f, f is float so every thing becomes float so i/f=1004.7619f
•In d*i, everything becomes double so d*i=11873.603

Operators
An operator is a symbol which refers the type of calculation to be performed in any
operation. Eg. +,-,* etc
An operand is the value or variable used with operators.
Eg.5+6 here 5 and 6 are operands
An accumulator is a variable which holds(accumulates) the result returned by an
expression.
Eg. x=y+6 , here x is an accumulator
A Binary operator takes two or more operand. Eg, + requires two or more values.
6+10
Unary operator takes single operand, eg c++; here ++ takes single operand called c.

Types of operators
•Arithmetic Operators
Performs arithmetic operations.
+,-,*,/,%(modulus)
•Arithmetic and assignment operators
• ++(increment) ++a, pre increment, a++ post increment
• --(decrement) --a, pre decrement --a pre decrement
•+= addition assignment
•-= subtraction assignment
•*= multiplication assignment
•/= division assignment
•%= modulus assignment
•Bitwise operators: These operators perform operation upon individual bits.
•& (Bitwise AND) 5 & 6=4
101 & 110=100
• | (bitwise or)
•~ bitwise NOT
•^ bitwise XOR 5^6=3
•101 ^110=011

Types of operators
>>(Bitwise right shift) 5>>2= 0 0000101>>2 = 00000001|01(01 is out)
<<(Bitwise left shift) 5<<2= 0 0000101<<2 =20 00|00010100 (00 is
out)
>>>(Unsigned right shift)-- above operators preserve sign but this does not care sign.
Int a=-124;
Int b=a>>>3;
Here 1 0000100>>>3 red means - sign
0001 000|100>>>3 (so -16) green means out

Types of operators
An operator is a symbol which refers the type of calculation to be performed in any
operation. Eg. +,-,* etc
An operand is the value or variable used with operators.
Eg.5+6 here 5 and 6 are operands
An accumulator is a variable which holds(accumulates) the result returned by an
expression.
Eg. x=y+6 , here x is an accumulator
A Binary operator takes two or more operands. Eg, + requires two or more values.
6+10
Unary operator takes single operand, eg c++; here ++ takes single operand called c.

Types of operators
How bitwise operators differ from other operators ? (QB)
Bitwise operators are special type of operators which perform operation for single bit.
This helps to manipulate each individual bit easily. There are many bitwise operators.
& (bitwise AND), ~ (Bitwise NOT), |(Bitwise OR), ^(Bitwise XOR), >> (right Shift),
<<(Left Shift) etc.
For example:
class Test{
int x=5;
int y=6;
int z=x & y;
System.out.println(“Z is “+z);
}
}
Here
5 means 101
6 means 110
Anding 100 means 4
This program outputs 4

Types of operators
How bitwise operators differ from other operators ? (QB) continued..
Other operators use operand as single number. These perform arithmetic and other
logical type of operations.
Eg int x=5;
int y=6;
int z=x+y;
Here z becomes 11

Types of operators
Post increment Vs. Pre increment ?
The increment and decrement operators such as ++ and – can be used before or after
operands.
If operator proceeds operand then it is pre increment or pre decrement. Pre increment
first increments the operand and returns result to the accumulator.
Eg. int x=5;
int y=++x;
Here y is 6 because when expression is called, x is first incremented and then value is
given to y.
And, Post increment has opposite nature, It first returns value to the accumulator and
the increments.
int x=5;
int y=x++;
Here y is still 5 because x first returns value to y and increments later.

Relational operators
Relational operators work with two operands which return either true or false but not
both.
>(Greater than)
< >= <= !=
Eg. 5>6 is false, 6<9 is true
Logical operators: These operators evaluate two or more relational operations
logically. Eg.
&& (logical AND)
|| (Logical OR)
!(Logical NOT)
Ternary operator(? :) this operator is used to evaluate an expression as if-else
statement and called ternary operator. Syntax is
<var1>=(<cond>)?<value1>:<value2>
Here, if condition becomes true, value1 will be assigned to var1 otherwise value2 will
be assigned

Short-Circuit Logical Operators
Java provides special version of AND(&&) or (||) as short circuit operator. Normally A
|| B gives true if one is true. So to determine the result Just it is enough to know the
value of A and no mater what B is. In the same way A && B gives false if A is false.
So java will not evaluate right hand operands if result is determined by left hand
operand. This is called short circuit operation.
Eg.
if(d!=0 && n/d>0) {
}
Here if d is 0 then d!=0 becomes false then java knows result will become false so it
will not evaluate n/d>0 this means possible runtime exception can be avoided.
If(d!=0 & n/d>0) {
}
Here both operands are evaluated so runtime error may occur if d is 0

int d=10;
int n=100;
if(d!=0 && n/d>5){
System.out.println(n/d);
}
else
{
System.out.println("Division not possible");
}
}
}
int d=0;
int n=100;
if(d!=0 && n/d>5){
}
else
{
}
}
}
int d=10;
int n=100;
if(d!=0 & n/d>5){
}
else
{
}
}
}
int d=0;
int n=100;
if(d!=0 & n/d>5){
}
else
{
System.out.println("Division not possible")
}
}
}

Output :
10
Output:
Diviison not possible
Output :
10
Output:
Exception: division by zero

Operator Precedence Order
Order
[], (),.
++,--,~,!
* , /, %
+, -
>>, <<,>>>
>, <, >=, <=
==, !=
&
^
|
&&
||
?:
=
What is operator precedence? What is the use
of? Operator. Give an example.QB
Operator precedence refers the order of
execution of operators in the given expression. It
tells which operator is used first in an
expression.
?: operator is used to evaluate an expression as
if-else statement and called ternary operator.
Syntax is
<var1>=(<cond>)?<value1>:<value2>
class Precedence{
int salary=10000;
int
tax=(salary>5000)?salary*10/100:salary*5/100;
System.out.println("Tax is "+tax);
}}

Control Structure
What are control flow statements?
Control flow refers the flow(path) of execution of program instructions. Normally all
programs have sequential flow where statements are executed from one after another.
But Java (like other programming language) provides the way to control that flow by
using control statements.
Java provides conditional control statements for selection(if,switch) statements, for
looping(for,while,do) and Unconditional branching statements like (break, continue,
return).
Selective Statements:
If construct:
It takes a condition and performs selection on the basis of result.
Syntax:
1) Single If : if(<condition>)
task1;
task2;
here task1 will only be selected if condition is true.

Control Structure
2) Single If-else : if(<condition>)
task1;
else
task2;
task3;
here task1 will only be selected if condition is true otherwise task2; but not
task3;
3) Block If : It allows us to execute multiple lines of code if condition satisfies or
dissatisfies.
if(<condition>){
task1;
task2;
}
if(<condition>){
task1;
task2;
}
else
{
task3;
task4;
}

Example:
//class name is Selection so save file as Selection.java
class Selection {
int age=10;
if(age>=18)
System.out.println(“You can vote”);
else
System.out.println(“You can not vote”);
}
}

Nested if
When if statement contains another if inside, this is called nested if. When else
statement is used with other multiple if, it refers nearest if.
class Nested{
int a=5,b=6,c=7,x,y;
if(a==5) {
if(b<20) x=b;
if(c>100)y=c;
else y=b;
}
}
}
*Here else is related to nearest if, marked with red color

int m=75,s=40,e=18,c=19;
int t=m+s+e+c;
String div=null;
float p=t/4;
if(p>=80)
{
div="Dist";
}
else
{
if(p>=60){
div="First";
}
else
{
if(p>=50){
div="Second";
}
else
{
div="Third";
}
}
}
System.out.println("You got "+div+" Division");
}
}

Switch
switch statement in java performs the task similar to multiple if-else. It takes an
expression and performs branching. Switch needs break for branching which
means jumping out. The expression must be byte,short,int,char only. We can also
use nested switch.
Syntax:
switch(expression)
{
case value1:
task1;
break;
case value2:
task2;
break;
.
.
.
default:
task;
}

public static void main(String args[]) throws IOException {
int day=5;
switch(day) {
case 1:
System.out.println("Sunday");
break;
case 2:
System.out.println("Monday");
break;
case 3:
System.out.println("Tuesday");
break;
case 4:
System.out.println("Wednesday");
break;
case 5:
System.out.println("Thursday");
break;
case 6:
System.out.println("Friday");
break;
default:
System.out.println("Saturday");
}
}
}

Looping(Iteration)
Looping is the process of executing one or more statements repetitively for
number of times . Looping continues as long as the condition is satisfied.
1) for loop:
for(init; condition; increment/decrement)
task;
Or
for(init; condition; increment/decrement) {
task1;
task2;
}
Where init is initial value

Example
Wap to print 1,11,111 upto 8th term (QB)
public static void main(String args[]) throws IOException {
int num=1,i;
for(i=1; i<=8; i++){
System.out.println(num+"t");
num=num*10+1;
}
}
}

While Loop
While loop checks condition first and performs repetition if condition remains
true.
Syntax:
Initialization
While(condition)
{
tasks;
increment/decreement
}
Eg. Print numbers from 1 to 100;
int n=1;
while(n<=100)
{
System.out.println(n);
n++;
}

While Loop
Wap to find the sum of digits of given Number(QB)
public class DigitSum{
int n=123;
int s=0,r;
while(n>0){
r=n%10;
s=s+r;
n=n/10;
}
System.out.println(s);
}
}

Do Loop
Do loop checks condition at last and continues repetition if condition remains true.
So if initially condition is false, loop executes at least once.
Syntax:
Initialization
do
{
tasks;
increment/decreement
} while(condition)
Eg. Print numbers from 1 to 100;
int n=1;
do
{
System.out.println(n);
n++;
} while(n<=100)

Do Loop
Wap to reverse the given digit
public class DigitSum{
int n=123;
int s=0,r;
while(n>0){
r=n%10;
s=s*10+r;
n=n/10;
}
}
}

Nested Loop
If one looping statement contains another loop inside, it is called nested loop.
When for uses another for then that is called nested for.
for(…………………………..) {
for(…………………..){
task;
}
}
If outer executes 5 times and inner loop has 4 times then outer repeats inner 5 times in
each loop. So total loop will be 5x4=20 times
Class Nested{
for(int i=1; i<=5; i++){
for(j=1; j<=4; j++){
System.out.println(“nested loop, I is “+i+” j is “+j);
}
}
}
Output :

Nested Loop
Nested loop, I is 1 j is 1

Using comma with for
Rewrite the program to reverse number
int n,s;
int r;
for(n=123,s=0; n>0; n=n/10){
r=n%10;
s=s*10+r;
}
}
}
Output: 321

Jump Statements
Java provides following jump statements:
1) break: this statement is used to exit from a loop. break statement can also be used to
exit from certain block.
Syntax:
break;
Or
break block_name;
class First {
for(int i=1; i<=100; i++){
System.out.print (i+” “);
if(i==5) break;
}
}
}
1 2 3 4 5

Jump Statements
2) continue: This statement forces to skip remaining code in the loop and continue to
early part of loop.
continue;
class First {
for(int i=1; i<=10; i++){
if(i==5) continue;
// 5 will not be printed because next code will be skipped
System.out.print (i+” “);
}
}
}
1 2 3 4 6 7 8 9 10

Jump Statements
3) return: This statement is used to return from function body. This causes remaining
code ina function to be skipped.
class First {
System.out.print ("Hello");
if(true) return;
System.out.print ("Hi");
}
}
Output:
Hello

Arrays
An array is a group of variables which are referred by common name. An array can
hold multiple values of similar type which can be accessed by using index.
• One dimensional Array: This type of array holds single row of data.
Declaring an array:
Syntax:
type var_name[]
Eg. int nums[];
Allocating Memory:
var_name=new type[size];
eg;.
nums=new int[10];
Direct method:
int nums[]=new int[10];
Alternate Direct method:
int[] nums=new int[10];

Arrays
Assigning values:
nums[0]=15;
nums[1]=20;
nums[2]=24’
Etc.
Direct assignment:
int[] odds={1,3,5,7};
Or
int odds[]={1,3,5,7};
Accessing value:
System.out.println(odds[0]); ---------- prints 1

Arrays
Example:
class First {
int[] odds={1,3,5,7,9};
int i;
for(i=0; i<odds.length;i++){
System.out.println(odds[i]);
}
}
}
Multidimensional Array: Multidimensional Array holds values in tabular format.
It is actually an array of arrays. To declare multidimensional array, we need to use
multiple sets of brackets. []
Example:
int a[][]=new int[2][3];
Or
int[][] a=new int[2][3];

Arrays
Assigning values in multi-dimensional array.
int a[][]={
{1,3,5},
{4,8,9}
};
Here
a[0][0] is 1 a[0][1] is 3 a[0][2] is 5
a[1][0] is 4 a[1][1] is 8 a[1][2] is 9

Arrays
Example:
class First {
int i,j;
int n[][]={
{1,8,7},
{2,5,9}
};
for(i=0; i<2; i++)
{
for(j=0; j<3; j++)
{
System.out.println(n[i][j]);
}
}
}
}

Variable size array
Variable size array is a type of multi-dimensional array where number of array elements
are not equal.
Wap to print following array (QB)
Int[][] a={{1,2,3},{4,5},{6,7,8,9,10,11},{12},{13,14}};
class First {
int[][] a={{1,2,3},{4,5},{6,7,8,9,10,11},{12},{13,14}};
int i;
for(i=0; i<4;i++){
for(int j=0; j<odds[i].length; j++){
System.out.print(odds[i][j]);
}
System.out.print("n");
}
}
}

Classes and methods
•Using Methods in a class requires :
•Method return type eg. Int float,char,void etc
•Function name
Syntax:
type methodName(paramater list) {
return value;
}
Here return is not required if method is defined with void keyword.
Parameter is the variable which is used to pass values inside methods.

Classes and methods
class First {
First obj=new First();
obj.greetings();
int result=obj.sum(55,50);
System.out.println("Sum is "+result);
}
void greetings(){
System.out.println("Hi, Good Morning n");
}
int sum(int a, int b){
return a+b;
}
}
Output:
Hi, Good Morning
Sum is 105

Classes and methods
In this example, obj is the instance of class First. We can access methods of First using . (dot)
operator. This example uses two functions. Greetings() uses void so no return is required and sum
uses return type as int and two parameters also.
new operator: This operator dynamically allocates memory for an object. It allocates memory
during runtime. When memory is insufficient then outOfMemory exception is raised.

Classes and methods
class MyRectangle{
int l;
int b;
void area(){
int a=l*b;
System.out.println("Area is "+a);
}
}
class First {
MyRectangle big,small; //declare reference object
big=new MyRectangle(); // allocate memory to big object
big.l=20;
big.b=15;
big.area();
small=new MyRectangle();
small.l=5;
small.b=3;
small.area();
}
}
Area is 300
Area is 15

Constructor
Constructor is similar to method but it is called automatically when object of the class is created. A constructor
has similar name to class. It is used to initialize the values upon creation of object. A constructor can take
parameters also. Consructor can also be overloaded.
class MyRectangle{
MyRectangle(){
System.out.println("Object created");
}
}
class First {
MyRectangle a;
a=new MyRectangle(); // here constructor is called
}
}
Output:
Object Created

Parameterized Constructor
class MyRectangle{
int length,breadth;
MyRectangle(int l,int b){
length=l;
breadth=b;
}
int area(){
return length*breadth;
}
int perimeter(){
return 2*(length+breadth);
}
}
class First {
MyRectangle a;
a=new MyRectangle(5,10); // here constructor is called
System.out.println("Area is "+a.area());
System.out.println("Perimeter is "+a.perimeter());
}
}
Area is 50
Perimeter is 30

Java Programming concept

Recommended

More Related Content

What's hot (20)

Viewers also liked (20)

Similar to Java Programming concept (20)

More from Prakash Poudel (20)

Recently uploaded (20)

Java Programming concept