CORE JAVA

CORE JAVA

JAVA

Object Oriented Program is a programming approach in which a problem domain is characterized as a set of objects that have a specific attributes and behavior. The objects are manipulated with a collection of functions called methods or services. The objects are classified into classes and subclasses. (or) An Object Oriented Programming organizes a program around its data, i.e., objects and a set of well-defined interfaces to that data. An object-oriented program can be characterized as data controlling access to code. Java is an Object Oriented Programming (OOP) language used to design an application, which will run securely over the network and work on wide range of platforms.

J2SE: - J2SE stands for Java 2 Standard Edition, it is a specification used to develop fundamental java application they may be standard or network.

J2SE = Core Java + Advanced Java

J2SE: - Java 2 Standard Edition

J2EE: - Java 2 Enterprise Edition

J2EE: - J2EE stands for Java 2 Enterprise Edition, it is a specification used to develop business solutions for network (or) J2EE is a specification that provides an environment to run the web components and the enterprise components.

J2ME: - Java 2 Micro Edition

J2ME: - J2ME stands for Java 2 Micro Edition, it is a specification used for developing wireless and Embedded System. Embedded System is software, which directly installed into hardware.

Difference between Java 1.4.1. and Java 1.5 [www.sunjava.com, www.javasoft.com]

Core Java Desktop Java

NIC Network Interface Card

Novel Network: - Net based softwaressEx: - Windows NT, UNIX.

Protocol: - This is also a program; it is a specification of set of rules to be followed by a computer in network.

When to send/receive data

How to send/receive data

Hand Shaking: - This means two Computers establishing a connection communicating with each other and finally disconnecting is called Hand shaking.

A Packet represents a group of bytes. IP means Internet Protocol address this is unique address this is given to Computers.

TCP/IP: - Transmission Control Protocol/Internet Protocol.

Client: - A Client is a machine that sends a request for some services to other Computer.

Server: - Server is a machine that receives requests from the Clients and provides services to the Client requests.

The main advantage of a network is resources sharing.

Web application: - A web application is a collection of Servlets, HTML pages, Classes and other resources that can bundle and run on the multiple Containers from multiple Vendors. Resources Sharing: -

Sharing memory

Sharing data

Sharing software

Sharing hardware

Sharing Processor

1969 Department of Defence (DOD), USA, Ken Thompson is introduced network. This network is called ARPANET.

( (

(

(AT&T Advanced Telephone Communication & Technology USA based Telephone Company.

Hyundai, British Telecom are also Telephone companies, these three companies are giant of the Telephone.

ISP: - It stands for Internet Service Provider. ISP is a person or an organization, who provides connection into internet. ISP should take direct connection to internet. (www.internic.com).

Bandwidth is a group of frequency.

American Congress Library is a biggest Library in the World; the second biggest Library is Lenin Glad Library in Masco, (Russia).

Q) What is an Interface? *****

Ans: - An Interface defines a protocol of behavior that can be implemented by any class anywhere in the class hierarchy. An interface defines a set of methods but doesnt implement them. A class that implements the interface agrees to implement all the methods defined in the interface, thereby agreeing to certain behavior.

An interface is a named collection of method definitions (without implementations). An interface can also declare constants.

Internet: - Internet is a network of Computers existing on the earth. Internet is a global network of all networks existing on the earth.

Connecting Internet types: -

Dialup Connection: -

Dialup connection main advantage is affordable to any one.

Disadvantage of Dialup connection is slow.

There is no security for data.

2. Leased line Connection: - It is a direct connection to internet.Advantages: -

High Security for data

Lightening Speed (i.e. high speed)

Disadvantages: -

Highly expensive.

The web browser software is installed on Internet Client.

Ex: - Internet Explorer, Mozilla, Fire fox, Netscape Navigator etc

The software that should be installed on Internet Server is Web Server.

Web Server: - A web server is a server that provides the implementation of HTTP protocol.

Ex: - Internet information Server (IIS), Apache Web Server, etc

Application Server: - An Application Server is a product that provides the facilities like taking care of transactions, taking care of security and simplifies the development of business logic (or) Application servers provides you with common middleware services, such as resource pooling, networking and more. Application server allows you to focus on your application and not worry about the middleware you need for a robust server side deployment.

Ex: - Microsoft Transactions Server (MT Server) from Microsoft, EJB containers like WebLogic, WebSphere, JBoss etc

Hypertext Transfer Protocol (HTTP) is widely used protocol on internet.

File Transfer Protocol (FTP), when we download a file from Internet.

Simple Mail Transfer Protocol (SMTP) is used to send mails on the internet.

Post Office Protocol (POP) is used to receive mails.

Programmer has: -1. To develop a web browser

2. To increase the capabilities of web browser

3. To develop a web server

4. To increase the capabilities of the web server

5. To develop protocol

Translator is a program that converts a computer program into machine language (Electric Pulses).

There are 3 types of translators -

1. Interpreter Interpreter translates line by line of computer program

2. Compiler Compiler translates all lines of program at a single time

3. AssemblerAssembler translates assembly language into machine language

C, C++, are not portable programs, they are system dependent because they can be executed only on that system where they are developed.

The first microprocessor is - 4 0 0 4

The next microprocessors are follows as below

8 0 0 8

8 0 8 5

8 0 8 6

8 0 2 8 6

8 0 3 8 6

8 0 4 8 6

8 0 5 8 6x, PI, PII, Celeron, PIII, AMD, PIV, PIV Pro

Why Java is suitable for Internet

The size of each instruction is 1 byte or 8 bits. There are around 210 byte code instructions are available

Byte code instruction is understand by JVM (Java Virtual Machine).Components of JVM

JVM

Sun Microsystems is developed the JVM program.

JVM convert byte code instruction into machine code. JVM understand every byte code instructions.

JVM will understand the byte code instruction & it will convert the byte code instructions into PIV processor understandable machine language instructions.

JVM will convert the byte code instructions into any type of processor understandable machine language instructions.

Java programs system independent.

JVM is system dependent.

Depending on operating system we have to download the operating system related JVM program.

.class file is system independent.

JVM is making as Java system independent.

Portability means giving same results on any type of system or machine.

Security Problems on Internet: -

1. Eves dropping: - Reading others data illegally on Internet, is called Eves dropping.

2. Tampering: - Not only reading others data but also modifying it on Internet, is called Tampering.

3. Impersonation: - A person acting as another person on Internet is called impersonation.

4. Virus: - Virus is a harmful program that can damage data, software & hardware of a system.

Virus was first developed by Pakistanis. Virus will spread to *.exe, *.sys, *.doc. but *.txt files cannot carry virus.

Solution for eves dropping & tampering encryption/decryption. Encryption means converting data into understandable data. Decryption means converting data back to readable form.

For impersonation, solution is digital signature file, containing personal information for identify the person in encrypted form. Digital signatures are developed in java.

Solution for virus is .class file. Security manager is program that identifies illegal code and information security polices. A .class is a text file virus cant be affected.

Why Java is suitable for Internet: -

Security problems on Internet are eliminated through java.

Java is a system independent; Java is executable on any platform.

In 1990, Sun Microsystems inc., USA is developed software for remotes. (James Gosling).

In 1993, Oak language is developed, by that time some company is registered Oak name, for this reason they named as Java.

In 1995, Sun world conference has given entire details of Java.

Features of Java: -

1. Simple: - Java is a simple programming language, learning and practicing java is easy because of its resemblance (Similarity) with C, C++.

2. Object Oriented: - Unlike C++, Java is a purely object oriented programming language.

Java = C++ - Complexity

An object is existing of everything in the world is an Object. An object has properties & performs actions.

Object initialization process: -

Default values ( initialization expressions ( initialization blocks ( constructors

Default values: -

float, double

-0.0F,0.0

boolean

-false

Reference variable

-null (not referring any object)

Char

-\u000 (or) a space

String

-Null

My class

-Null

3. Distributed: - Java is designed for use on networks. It has extensive libraries, which work in agreement with TCP/IP. Java uses protocols like HTTP & FTP.

4. Robust: - Java programs will not crash because of its exception handling and its memory management feature.

Pointers are eliminated from Java due to: -

1. These are lead to complex programs

2. Using pointers harmful programs are written.

3. Pointers may crash a program.

Method is a function; Function represents set of instructions to perform the results. A method must be starts with lowercase. A method will returns a void or any valid return type. A method can be inherited and it can be overloaded or overridden. A method has called explicitly.

Function can be written inside & outside of the class, but a method is a function, it is written only inside of a class. A function can be called & executed itself.

Q) What is the difference between method and function? *****

Ans: - A method is a function written only inside of a class but functions can be written any where in class i.e. inside or outside of the class. In java we will write only methods. Writing a function outside the class is not possible in java.

Methods or functions can store only some temporary variables or local variables, but not permanent variables.

A class is a model or idea or plan to create objects or Class is a group of objects. Class doesnt exist really because it is only an idea but objects exist really.

A class will also contain variables & methods. An object will also contain variables & methods. In every java program we must create a single class. C++ is not purely Object oriented programming Internet is a distributed technology. Java is suitable for distributed technology. Robust means strong, in java we can write strong programs. Exception means runtime error

JVM will allot memory to what ever we required memory.

Unused memory released or free it by JVM

Garbage Collector will delocate or removes memory for unreferenced or unused objects and variables.

Garbage Collector can be called explicitly but there no gurantee that the garbage collector executes or not at that point.

Q) What algorithm is used by garbage collector to remove variables or objects from memory? *****

Ans: - Mark & Sweep algorithm.

Q) What is the difference between .exe and .class file? *****

Ans: - .exe file contains machine language instructions for the microprocessor. It is system dependent. .class file contains byte instructions for JVM. It is system independent.

In JVM class loader sub system will allot the memory required for program.

Garbage memory delocates the memory.

5. Secure: - Java is designed for use on internet. Java enables the construction of virus-free, tamper free systems.

6. Architecture Neutral: - Javas byte code is not machine dependent. It can be run any machine with any processor and any operating system.

7. Portable: - Java does not have implement-dependent aspects. So the results will be same on all machines. Portable means yielding same results on different machines.

8. Interpreted: - Java programs are compiled to generate bye code. This byte code can be downloaded and interpreted by the interpreter. JVM contain interpreter.

9. High performance: - Along with interpreter there will JIT (Just in time compiler), which enhances the speed of execution.

Variable: - An item of data named by identifier. Each variable has a type, such as int or object and a scope. Reference Variable: - A data element whose value is in an address.

Local Variable: - A data item known within a block, but inaccessible to the code outside the block.

For example, any variable defined within a method is a local variable and cant be used outside the method.

A local variable life cycle ends when the execution of method completed. A local variable should declared within a method body and it must be initialized when we are declaring in a method, because it doesnt takes default values.Path Variable: - It is exterenal command file. A path variable is used to specify where the executable files are.

Ex: - javac.exe, java.exe, javap.exe etc. Argument: - A data item specified in a method called an argument. An argument can be a literal value, a variable or an expression (or) an argument is a value that is passed to the method when it is invoked.

Parameter: - While defining a method, variables passed in the method called as parameter (or) Parameters are variables defined by method that receives values when a method is called.

Parameters are useful to pass the variables from objects to the constructor.

Method parameters are local variables to receive the data from out side for method.

Parameters are useful to receive the values from outside to main method.

What is the difference between parameter and argument? *****

Ans: - While defining method, variables passed in the method called as parameter. While using those methods, values passed to those variables called arguments.

Process: A virtual address space containing one or more threads (or) a program under execution is also called as process.

Peer: - In networking, any functional unit in the same layer as another entity.

Expression: - An expression is a series of variables, operators, and methods calls, (constructed according to the syntax of the language) that evaluates to single value.

How would you detect and minimise memory leaks in Java: -

In Java memory leaks are caused by poor program design where object references are long lived and the garbage collector is unable to reclaim those objects.

Detecting memory leaks:

Use tools like JProbe, OptimizeIt etc to detect memory leaks.

Use operating system process monitors like task manager on NT systems, ps, vmstat, iostat, netstat etc on UNIX systems.

Write your own utility class with the help of totalMemory() and freeMemory() methods in the Java Runtime class. Place these calls in your code strategically for pre and post memory recording where you suspect to be causing memory leaks. An even better approach than a utility class is using dynamic proxies or Aspect Oriented Programming (AOP) for pre and post memory recording where you have the control of activating memory measurement only when needed.

Minimising memory leaks:

In Java, typically memory leak occurs when an object of a longer lifecycle has a reference to objects of a short life cycle. This prevents the objects with short life cycle being garbage collected. The developer must remember to remove the references to the short-lived objects from the long-lived objects. Objects with the same life cycle do not cause any issues because the garbage collector is smart enough to deal with the circular references.JVM Architecture: - JVM 1.4.1 version developed by Hotspot.

Class loader subsystem does the following things: -

1. It will load .class file into memory (RAM)

2. It will verify byte code of that .class file.

3. It will allot the required memory for the program.

This memory is divided into five parts; they are called runtime data areas.

1. Method area: - It stores class code, static variables, static blocks and method code.

2. Heap area: - Objects are created on Heap. JVM creates objects on Heap.

3. Java Stacks: - Java stacks are used to execute the java methods. Java stacks will have frames. On each frame a separate method is executed.

4. PC Registers: - These registers contain the address of that instruction to be executed by the processor.

5. Native method stacks: - It is a method written in a language other than java. Native method stacks places when native methods are executed.

Note: - Native method interface links header files to a native method while it is being executing.

Execution engine contains interpreter & JIT compiler, which translates byte code into machine language.

How JIT compiles converts byte codes.

Ex: - print a; 2sec

print b; 2sec

Repeat the loop 10times;

print a; 2 + 2

Hotspot is the block code of given to JIT compiler for execution.

10. Multithread: - Thread means an execution or processing group of statements. Executing different parts of a program simultaneously at a time by using more than one thread is called Multithreading. This is an essential feature of to design server side programs.

11. Dynamic: - It means at runtime, we can develop programs in java, which dynamically change on Internet. (Ex: Applets).

In java entire memory will be dynamic memory.

Java Programming: -

Comments represent description of the features of a program.

The main advantages of comments are readability of the program is increased.

There are 3 types of comments in Java. They are

1. Single line comments: - It represents only one line as comment. Single line comments start with //.

Ex: - //Welcome INet Solv

//welcome to Java

2. Multi line Comments: - They represents a group of lines as comment. They starts with /* and end with */

Ex: - /*Welcome to India*/

3. Java documentation Comments: - They starts with /** and end with */.

Ex: - /**Welcome to BTCE*/

These comments are useful to create .html documents from .java programs.API Document: - API stands for Application programming Interface. It is a .html document that contains description of all the features of a software or a product or a technology. API document does not contain code. Javadoc complier is used for this.

Comments are non executable statements. These 3 types of comments are not executable by java compiler or JVM compiler.

In Java we can define/write any number of classes in a single class. Out of n number of classes we are writing in a single class only one can be defined as public class, because the name of the class should be public class.

If we need all the classes as public we have to decalred/write sepeartely each class as public.

Example Program: -

/*This is our first Java program.

To display a message

Author: INet Solv team

Version: V 1.0

Project: Proxyz 1.11

*/

//Starting a program in Java

import java.lang.system;

import java.lang.string; or in the place of two steps directly we can write as below

import java.lang.*;

class First

{

main()

{

---------------

---------------

---------------

}

}

Q) What is the difference between #include and import statements? *****

Ans: - #include makes C/C++ compiler to copy the header file into a C/C++ program. Thus it wastes the memory and processor time.

import will makes the JVM to go to a particular class, it executes the code there and then it comeback to the program and substitute the results in the program.

JRE: - It stands for Java runtime environment.

JRE = JVM + Java library

If java programs have to run we required the JVM and java library. JVM will starts execution of java program from main method only.

String represents group of characters.

Array represents group of elements. Array denotes with [ ]

The values passed to the main method are called command line arguments.

Void means no value (i.e. it returns no value).

import java.lang.*;

class First

{

main()

{

-------------

-------------

-------------

}

}

To call method there are two steps: -

1. To create on object to the class to which method belongs

Classname obj = new Classname();

Ex: - First f = new First();

((f = object)

2. Call the method using object name.methodname

Obj.methodName();

Ex: - f.main();

Objects are created dynamically (runtime) by JVM

Static method: - It is a method that can be called and executed without creating an object.

Public: - It means available outside the object. JVM will not run the public without writing String args[]. JVM could not executes the main method.

For single character in java we have to write in single quotations like as a and for integer dont write in any quotations.

System.out: - Out is a variable of a system class. It is a static variable or filed.

Save the name with in double quotations to avoid the extension of .txt.

System.out.println(): -

System: - System is a predefined final class which is defined in java.lang package that provides the access to the system resources like Keyboard, monitor etc and to get and set the properties associated with java runtime system. All the methods in the System class are static methods.

System Class: - A System class will have static members, they are as follows below PrintStream out, err

InputStream in;

arrayCopy(Object[ ], st, end, Object[ ], st)

exit(int)

loadLibrary(String)

get/setSecurityManager(SecurityManager)

String getProperty(String)

String getProperties(String str) (getProperties() method is usefull to get the JVM name, version, properties of JVM and etc.).

Properties getProperties() (Property is a class in java.util package and getProperties() method is usefull to set/get the property of a class, etc.).

gc()

out: - out is a static variable defined in a System class of the type PrintStream class, which provides all of the formatting capabilities we have been using from the system file handler or out is the PrintStream object.

println(): - println() is a built-in overloaded method in the out object or the PrintStream object supports the print() or println() methods for all data types.

We can provide a security for a class as below:

public static void main(String args[ ]){

System.setSecurityManager(new SecurityManager());

---------------

---------------

---------------

}

To Compile: -

C:\rnr>javac First.java(

C:\rnr>java First(

Welcome to java

Class, interface contains methods.

Function is written inside & outside of the class, but methods are written only inside of the class.

Command line arguments are passed some values to the main method.

Main method does not return any value. Void means no value.

JVM always starts execution of the statements inside of the main method.

Public is written to make available main method to the JVM.

Ex 2: -

//To find sum of two numbers

import java.lang.*;

((* is a String class)

class Sum

{

({ ----This is for starting of class)

public static void main(String args[ ])(String args[ ] is a parameter)

{

//Variables

int a, b;

//Store data into variables

a = 10;

b = 15;

//Now find sum

int c = a + b;

//display the result

System.out.println(Sum = ,+c);

}

}

((} ----This is for ending of class)

(or)

//To find sum of two numbers

import java.lang.*;

class Sum

{

public static void main(String args[ ])

{

//Variables

int a, b;

//Store data into variables

a = 10;

b = 15;

//display the result

System.out.println(Sum = + (a+b));

}

}

Save the above file (with class name compulsory) as Sum.java

C:\rnr>javac Sum.java(

(This is for program compilation)

C:\rnr>java Sum.java(

(This is to run the program)

Note: -

1. print method displays the results and keeps the cursor in the same line.

2. println method displays the results and then throws the cursor to the next line.

S. No.Back slash codes

or escape sequenceMeaning

1.\nNew line

2.\rEnter key

3.\tHorizontal tab

4.\bBackspace key

5.\\\

6.\

7.\

In java every statement must end with semi colon (;).

Java is case sensitive programming language.

Naming Conventions in Java: - 1. Each word of class names and interface names start with a capital letter.

Ex: - String, StringBuffer, DataInputStream, ActionListener etc2. Packages names in java are written in all small letters.

Ex: - java.awt, java.io, java.swing etc

3. Method names start with a small letter, then each word start with a capital letter.

Ex: - println(), getChars, readLine(); getNumberInstance() etc

4. Variables names also follow the above rule.

Ex: age, empName, employee_Net_Sal etc

5. Constant variables should be written using all capital letters.

Ex: - PI, MAX_VALUE, FONT.BOLD

Note: - java.lang is a package that is by default imported into every java program. The other packages must be imported in java program.

Important packages of Java: -

1. java.lang: - This package got primary classes and interfaces essential for java language. It consists of wrapper classes, strings, multithreading etc.

Wrapper classes are useful to create objects

String is a class in java

Multithreading means create several threads (processes executing) at a time.

2. java.util (util = utility): - This package contains useful classes and interfaces like stack, LinkedList, Hashtable, Arrays etc.

3. java.io: - This package handles files and input/output related tasks.

4. java.awt (awt = abstract window toolkit): - This package helps to develop GUI (Graphical user interface). It consists of 2 important sub packages, namely: java.awt.event and java.awt.image.

5. javax.swing: - x stands for extended package. The classes in this package have been derived from other package. This package helps to develop GUI like java.awt.

6. java.net: - net stands for network. Client/Server programming can be done using this package. It uses TCP/IP internally.

7. java.applet: - Applets are small intelligent programs, which travel form one place to another place on internet.

8. java.sql: - sql stands for structure query language. This package helps to connect to databases like oracle and utilize them in java.

9. java.beans: - Beans are software reusable components. They can be developed using this package.

10. java.rmi: - rmi means remote method invocation. The objects, which exist on one computer in the network, can be invoked from another computer and can be used.

11. javax.servlet: - Servlets are server side programs which communicate several clients at a time. Servlets are server side programs, which handle clients. This package is useful to develop servlets.

Class is model for creating objects. In case we have to write methods & variables. Data types represent the type data stored into variable (i.e. into memory locations).Data types and literals: - A data type represents the type of data stores in memory (variable).

Integer data type: - It represents integer numbers i.e. the numbers without decimal points.

Subtype: -

S. No.Data typeMemory sizeMin & Max value

1.byte1 byte-128 to 127

2.short2 bytes-32768 to +32767

3.int4 bytes-2147483648 to +2147483647

4.long8 bytes-9223372036854775808 to +9223372036854775807 (or) -9.2 x 10-18 to 9.2 x 1018

Ex: - byte r.no = 10(0 - literal)

Literal means the constant value being directly storing into variable.

long x = 150L;

L means take that number forcibly as long integer to allot the memory as user defined.

float data types: - They can handle numbers with decimal points. Such numbers called floating data type.

Sub type: -

S. No.Data typeMemory sizeMin & Max value

1.(Single precision ) float4 bytes-3.4e38 to + 3.4e38

2.Double precision 8 bytes-1.7e308 to + 1.7e308

Q.) What is the difference between float and double? *****

Ans: -float can represents up to 7 digits after decimal point accurately.

Double can represents up to 15 digits after decimal point accurately.

Ex: - float PI = 3.142F; F represents forcing the JVM to take the value as float because JVM defaultly takes any decimal values as double.

Character data type: - It represents a single characters.

S. No.Data typeMemory SizeMin & Max value

1.Char2 bytes0 to 65535

Ex: - char ch = x;

ASCII American standard code for information interchange.

S. No.Data typeMemory SizeMin & Max value

1.char2 bytes0 to 65535

2.byte1 byte-128 to 127

3.short2 bytes-32768 to +32767

4.int4 bytes-2147483648 to +2147483647

5.long8 bytes-9223372036854775808 to +9223372036854775807 (or) -9.2 x 10-18 to 9.2 x 1018

6.float4 bytes-3.4e38 to + 3.4e38

7.double8 bytes-1.7e308 to + 1.7e308

8.boolean1 bit0 or 1

Keyboard consists 114keys. Keyboard consists up to 200 characters only.

Q) What is Unicode? *****

Ans: -Unicode is specification that includes the alphabetic of all international languages into java character set. Unicode uses 2 bytes to represent single character.

4. String data types: - String represents a group of characters. Strings are objects of string class in java.

Ex: - String name Inet solv;

String str = new String (A String);

Boolean data type: - They store either true or false. It can handle only two values.

Ex: - boolean response = true;

Complete list of Java keywords: -

abstractbooleanBreakbytecasecatch

charclassConstcontinuedefaultdo

doubleelseExtendsfinalfinallyfloat

for gotoIfimplementsImportinstanceof

intinterfaceLongnativenewpackage

privateprotectedPublicreturnshortstatic

strictfpsuperSwitchsynchronizedthisthrow

throwstransientTryvoidvolatilewhile

assert

Transient: - A value of an instance variable in a class will not persistent when the object is stored, such an instance variable can be specified as transient variable, indicating that its value need not be saved when objects of its classes are put in persistence storage or it prevents fields from ever being serialized. Transient fields are always skipped when objects are serialized.

Transient variables arent appropriate for equals() and hashCode() methods.

Note: - That the transient modifier cannot be specified for static variables as these do not belong to objects.

Volatile: - In multithreading environment, threads might cache the values of member variable for efficiency reason. Since threads can share a variable, it is then vital that reading & writing of the value in the copies and the master variable do not result in any inconsistency. As these variables values could be changed unexpectedly. The volatile modifier can be used to inform the compiler that it should not attempt to perform optimization on the variable.

instanceOf: - The instanceof operator is used for object reference variables only, and you can use it to check whether an object is of a particular type. By type, we mean class or interface-in other words, if the object referred to by the variable on the left side of the operator passes the IS-A test for the class or interface type on the rightside. Even if the object being tested is not an actual instantiation of the class type on the right side of the operator, instanceof will still return true if the object being compared is assignment compatible with the type on the right.

class A

{

public static void main (String [] args)

{

String s = new String("foo");

if (s instanceof String) {

System.out.print("s is a String");

}

}Operator: - An operator is a symbol that represents an operation. `

a + b

(( a, b are operands, + is the operator)

Operand: - An operand is a variable on which operator acts upon.

An operator may act upon a single operand. It is called unary operator. If an operator acts upon two operands is called binary operand. If an operator acts on three operands is called ternary operand.

Operators in Java: -

1. Arithmetic Operators: -

+ - * / %

2. Unary Operators: -

- ++ --3. Assignment Operators: -

= += -= *= /= %=

4. Relational Operators: -

===!=

5. Logical Operators: -

&&||!

6. Boolean Operators: -

& |!

7. Bitwise Operator: -

a) Bitwise Compliment: -~

b) Bitwise and: -

&

c) Bitwise or: -

|

d) Bitwise xor: -

^

e) Bitwise left shift

>

8. Ternary Operator (Conditional Operator): -?:

9. Dot Operator (.): -

a) To refer a class in a package: -java.util.Date

b) To refer a method in class: - math.pow()emp.getsal()

c) To refer a variable in a class: -Employee.name, emp.name

10. Instanceof Operator: - To test whether an object belongs to a class.

Ex: - emp instanceof Employee.

Arithmetic Operators: - These operators perform basic arithmetic calculations like addition, subtraction, etc

Ex: - a = 13, b = 5

S. No.OperatorMeaningExampleResult

1.+Additiona + b18

2.-Subtractiona b8

3.*Multiplicationa * b65

4./Divisiona/b2.6

5.%Modulus operator (Remainder of division)a% b3

Unary Operators or Unary minus (-) Operator: - This operator negates the value of a variable. (Negation means converting value into + value vice versa).

Ex: - int x = -5;

System.out.printlin(x);

-5

System.out.printlin(-x);

5

System.out.printlin(-(-x));

-5

System.out.printlin(-(-(-x)));

-5

Increment Operator (++): - This operator increases the value of a variable by one.

Ex: - int x = 1;

++x (2

x++ ( 3

x = x + 1 ( 4

Writing ++ before a variable name is called pre incrementation. Writing ++ after a variable name is called post incrementation.

In pre incrementation, incrementation is done first any other task is done next.

In post incrementation any other task is done first, incrementation is done at the end.

Ex. 1: - int x = 1;

int x = 1;

S.o.println(x);

S.o.println(x)

S.o.println(++x);

S.0.println(x++);

S.o.println(x);

S.o.println(x);

Output

Output1 1

2 1

2

2

Ex. 2: -a = 1;

a = 1;

b = 2;

b = 2;

a = ++b;

a = b++;

a = 3

a = 2

b = 3

b = 3

Ex 3: - What is the value of the following expression, if a = 7?

++a*a++;

[ b]

a) 49

b) 64

c) 56

d) 72

e) None of these

Decrement Operator (--): - This operator decreases the value of a variable by one.

int x = 1;

--x ( 0

x-- ( -1

x = x 1 ( - 2

Writing before a variable is called pre decrementation, writing after a variable is called post decrementation.

Assignment Operator (=): -

1. It is used to store a value into a variable.

Ex: - int x = 15;2. It can store the value of variable into another variable.

Ex: - int y = x;

3. It can store the value of an expression into a variable.

Ex: - int z = x + y 10;

Note: - At the left hand side of assignment we should use only one variable.

Compact Notation: -

a = a + 10 ( a +=10

b = b 100(b -=10

j = k * j(j *=k

i = i/10;(i/=10

p = p%10( p%=10

Relational Operators: - These operators are useful to compare two quantities. They are used to constant conditions.

> < >=b)..;

if(a==100);

if(x!=y)...;

Logical Operators: - These operators are useful to combine more than one condition. Combining more than one condition called Compound condition.

&& - and|| = or

! - not

Ex: - if(a>b && b>c)...;

if(a==100||b=50)...;

if(!(x==1));

Boolean Operator: - These operators act upon Boolean variables and they return Boolean value.

&-Boolean and

|-Boolean or

boolean a = true;

boolean b = false;

a & b- false

a & a- true

b | b- false

!a- false

!b- true

Bitwise Operators: - These operators act upon individual bits of a number.

Convert 45 into binary: - Divide the number successively by 2 and table remainders from bottom to top.

45

0 0 1 0 1 1 0 1

22 1

11 0

5 1

2 1

1 0

0 1

Converting 00101101 into decimal: - Multiply the bits by the powers of 2 & take the sum of those products.

00101101

xxxxxxxx

27 +26 +25 +24 +23 +22 +21 +20

0 +0 +32 +0 +8 +0 +0 +1 = 45

Bitwise Compliment (~): - This operator gives complement from of a number.

Ex: - int x = 10;

~x = -11;

Bitwise and (&): - This operator performs anding operations on individual bits

aba & bThis table is called truth table. It means, it shows

00 0

input and output bits

01 1

10 0

11 1

Ex: - x = 10 y = 11, x & y =?

x = 00001010

y=00001011

x & y=00001010 = 10

Bitwise or (|): - This operator performs or-ing operations on individual bits

aba | b

00 0

01 1

10 1

11 1

Ex: - x = 10 y = 11, x | y =?

x = 00001010

y=00001011

x | y=00001011 = 11

Bitwise Xor (^): - ^ is called as Circum flex or Cap or caret. This operator performs exclusively oring operations on individual bits

aba | b

00 0

01 1

10 1

11 0

Ex: - x = 10 y = 11, x ^ y =?

x = 00001010

y=00001011

x ^ y=00000001 = 1

Bitwise left shift (2

x >> 2

x = 1000001010

x >> 200000010 = 2

Bitwise zero fill right shift (>>>): -

Q) What is the difference >> and >>>? *****

Ans: ->> shifts the bits towards right and also preserves the sign bit (0 for positive and 1 for negative sign).

>>> also shifts the bits towards right but does not preserve the sign bit. It always fills the sign bit with 0. For this reason it is called zero fill right shift.

Ex: - //Bitwise operators

class Bits{

public static void main (String args[ ]){

byte x,y;

x = 10;

y = 11;

System.out.println(~x = +(~x));

System.out.println(x & y = +(x&y));

System.out.println(x | y = +(x|y));

System.out.println(x ^ y = +(x^y));

System.out.println(x >y));

}

}

Ternary Operator: - This operator acts on three variables i.e. it will takes three variables.

This operator works like a conditional if-else statement. So this operator is called as conditional operator.

Syntax: -

var = exp1?exp2:exp;

max = (a>b)?a : b;

(or)if(a>b)

max = a;

else

max = b;

dot (.) operator: -

1. packagename.classname (to refer classname)

java.io.BufferedReader

2. classname.var or objectname.var (to refer variable)

System.outemp.name

3. classname.method() or objectname.method() (to refer method)]

Math.sqrt()

br.read

instanceOf operator: - It is denoted as instanceof. It is used to test whether the object belongs to that class or not.

Syntax: - objectname instanceof classname

Ex: - br instanceof BufferedReader

This operator returns true of false i.e Boolean values.

Executing the statements one by one by JVM is called sequential execution. In sequential execution programmers does not have better control on the flow of execution.

In Random execution the programmer can executive any statement directly or repeatedly. This gives better control for the programmer on the flow of execution.

Random execution is possible by using control statements.

Control Statements: - Control statements modify the flow of execution and give better control for the programmer on the flow of execution. Without control statements programmers can not able to write better programs.

1. ifelse statement

4. for loop

7. continue statement

2. do.while loop

5. switch statement

8. return statement

3. while loop

6. break statement

A loop can be executed repeatedly. A statement can be executed once only.

Ifelse statement: - This statement performs a task (one or more statement) depending upon whether a condition is true or not.

Syntax1: - if(condition)

statement1;

[else statement2;]

Ex: - //Test if a given number is +ve or ve

class Demo

{

public static void main (String args[ ])

{

int x;

x = -15;

if(x==0)

System.out.println(It is zero);

else if(x>0)

System.out.println(x+ is positive);

else

System.out.println(x+ is negative);

}

}

C:\rnr\javac Demo.java(C:\rnr\java Demo(Output: - -15 is negative.

Syntax 2: -

if(condition1)

if(condition2)

if(condition3)

statement1;

else statement2;

else statement3;

else statement4;

Dowhile loop: - This loop repeatedly executes a group of statements as long as a given condition is true.

Storing starting value into the variable is called initialization.

Syntax: -do

{

statements;

}while(condition);

Ex: - //To display numbers from 1 to 10

Class Demo

{

public static void main(Static args[ ])

{

int n = 1;

do{

System.out.println(n+ );

n++;

}while(n