Basic program

       Welcome to programming practice 

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Feature of java

Features of Java

Features of any programming language is nothing but the service or basic facilities provided by the language to the programmers. The java language provides the following features.

Simple:-

• Looks familiar to existing programmers: related to C and C++:
• Omits many rarely used, poorly understood, confusing features of C++, like operator overloading, multiple inheritance, automatic coercions, etc.
• Contains no goto statement, but break and continue
• Has no header files and eliminated C preprocessor
• Eliminates much redundancy (e.g. no structs, unions, or functions)
• has no pointers
• Added features to simplify:
• Garbage collection, so the programmer won't have to worry about storage management, which leads to fewer bugs.
• A rich predefined class library

Object-Oriented:-

Java is an object-oriented language, which means that you focus on the data in your application and methods that manipulate that data, rather than thinking strictly in terms of procedures.

In an object-oriented system, a class is a collection of data and methods that operate on that data. Taken together, the data and methods describe the state and behavior of an object. Classes are arranged in a hierarchy, so that a subclass can inherit behavior from its superclass.

Java comes with an extensive set of classes, arranged in packages, that you can use in your programs.

Portable:-

java goes further than just being architecture-neutral:

no "implementation dependent" notes in the spec (arithmetic and evaluation order)

standard libraries hide system differences

the Java environment itself is also portable: the portability boundary is POSIX compliant

 Platform Independent:-

A platform is the hardware or software environment in which a program runs.

There are two types of platforms software-based and hardware-based. Java provides software-based platform.

The Java platform differs from most other platforms in the sense that it is a software-based platform that runs on the top of other hardware-based platforms. It has two components:

1. Runtime Environment
2. API(Application Programming Interface)

Java code can be run on multiple platforms e.g. Windows, Linux, Sun Solaris, Mac/OS etc. Java code is compiled by the compiler and converted into bytecode. This bytecode is a platform-independent code because it can be run on multiple platforms i.e. Write Once and Run Anywhere(WORA).

Secured:-

Security is an important concern, since Java is meant to be used in networked environments. Without some assurance of security, you certainly wouldn't want to download an applet from a random site on the net and let it run on your computer. Java's memory allocation model is one of its main defenses against malicious code (e.g can't cast integers to pointers, so can't forge access). Furthermore:

access restrictions are enforced (public, private)

byte codes are verified, which copes with the threat of a hostile compiler

Robust:-

Java has been designed for writing highly reliable or robust software:

language restrictions (e.g. no pointer arithmetic and real arrays) to make it impossible for                     applications to smash memory (e.g overwriting memory and corrupting data)

Java does automatic garbage collection, which prevents memory leaks

extensive compile-time checking so bugs can be found early; this is repeated at runtime for                  flexibilty and to check consistency

Architectural neutral:-

compiler generates bytecodes, which have nothing to do with a particular computer architecture

easy to interpret on any machine

Dynamic:-

Java was designed to adapt to an evolving environment:

Even after binaries have been released, they can adapt to a changing environment

Java loads in classes as they are needed, even from across the network

It defers many decisions (like object layout) to runtime, which solves many of the version                    problems that C++ has

Dynamic linking is the only kind there is

Interpreted:-

It is one of the highly interpreted programming languages.

High performance:-

Java is faster than traditional interpretation since byte code is "close" to native code still somewhat slower than a compiled language (e.g., C++) Multi-threaded:- A thread is like a separate program, executing concurrently. We can write Java programs that deal with many tasks at once by defining multiple threads. The main advantage of multi-threading is that it doesn't occupy memory for each thread. It shares a common memory area. Threads are important for multi-media, Web applications etc. Distributed:- We can create distributed applications in java. RMI and EJB are used for creating distributed applications. We may access files by calling the methods from any machine on the internet.

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Environment of Java

How to Set Path and Classpath in Java

Path Variable

Path variable is set for providing path for all Java tools like java, javac, javap, javah, jar, appletviewer which are used in java programming. All these tools are available in bin folders so we set path upto bin folders.

Classpath Variable

Classpath variable is set for providing a path for predefined Java classes which is used in our application. All classes are available in lib/rt.jar so we set classpath upto lib/rt.jar.

Why set path ?

The following programming error is generally for all Java programmers when they compile any Java program.

'javac' is not recognized as an internal or external command, operable program or batch file.

When you get this type of error, then your operating system cannot find the Java compiler (javac). To solve this error you need to set the PATH variable.

Javac is a tool which is available in bin folder so you must set the PATH upto bin folder. In a bin folder all tools are available like javap, javah, jar, javac, java, appletviewer etc. All these tools are used for different-different purpose.

set the path and classpath

Go on my computer icon and right click, after that click on properties option.

Now click on advance setting

Click on advance

Click on Advance variables

Click on new button which is below the first box.

Now one dilog box is appear, now ignore this but do not close.

Now open my computer open c:/ > Programs Files > java > java1.6.0 > bin copy this path

Now come back on previous open dilogbox and write variable name 'path' and for variable value paste all copied path upto the bin folder. Put .; at the end. It (.) selects all the tools from the bin folder.

Now open my computer open c:/ > Programs Files > java > java1.6.0 > jre > lib > rt.jar copy this path

Note: rt.jar is available in lib folder this jar files contains all classes of jdk.

Now again come back on Environment variable dilogbox and click on new. Now one box is open and write path variable as 'classpath' and for variable value paste all copied paths upto rt.jar. Put .; at the end. It (.) selects all the classes from lib folder.

  

NOTE:-Finally after set classpath Restart your system, or you can re-open command prompt

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Path vs classpath

differences are like... 

1).Path is an environment variable which is used by the operating system to find the executables. 

Classpath is an environment variable which is used by the Java compiler to find the path, of classes.ie in J2EE we give the path of jar files. 


2).PATH is nothing but setting up an environment for operating system. Operating System will look in this PATH for executables. 

Classpath is nothing but setting up the environment for Java. Java will use to find compiled classes 

3).Path refers to the system while classpath refers to the Developing Envornment. 

In path we set the path of executables while in 
classpath we set path of jars for compiling classes.

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History of Java

History of Java

Java language developed by company Sun Microsystems and the creator is Jamesh Gosling.

Story behind development of Java

Sun Microsystems Started by a group of the students who are studing in Standard University. These people found the problem in their room with electronic consumable remote. That means one electronic consumable control doesn't work on another electronics consumable. These people want to develop a common remote control which is controlling all the electronic consumables so they contact James Gosling and requested for the projects. Sun Microsystems started by a group of students out of them one person also Indian whose name Vinode Khosla.

James Gosling and his team members given the project name as Green started in the year 1990 and common remote control completed in the year 1992.

The James Gosling team develops a new language called as OAK But this name is already selected by any other company renamed as Java, but Java has no meaning representation of Island in Indonesia. The unofficial abbreviation of Java is Just Another Virtual Analyzer (JAVA).

Java Version History

Now a day 8 versions of java are released, which is listed below with realizing date.

• JDK Alpha and Beta (1995)
• JDK 1.0 (23rd Jan, 1996)
• JDK 1.1 (19th Feb, 1997)
• J2SE 1.2 (8th Dec, 1998)
• J2SE 1.3 (8th May, 2000)
• J2SE 1.4 (6th Feb, 2002)
• J2SE 5.0 (30th Sep, 2004)
• Java SE 6 (11th Dec, 2006)
• Java SE 7 (28th July, 2011)
• Java SE 8 (18th March, 2014)

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Introduction to java programming

Introduction to java programming

Java is a programming language created by James Gosling from Sun Microsystems (Sun) in 1991. The target of Java is to write a program once and then run this program on multiple operating systems. The first publicly available version of Java (Java 1.0) was released in 1995. Sun Microsystems was acquired by the Oracle Corporation in 2010. Oracle has now the steermanship for Java. In 2006 Sun started to make Java available under the GNU General Public License (GPL). Oracle continues this project called OpenJDK.

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ASCII character codes

Table of 8-bit ASCII Character Codes

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Characters in 8-bit ASCII.

Decimal	Octal	Hex	Binary	Value	Description
000	000	000	0000 0000	NUL	"null" character
001	001	001	0000 0001	SOH	start of header
002	002	002	0000 0010	STX	start of text
003	003	003	0000 0011	ETX	end of text
004	004	004	0000 0100	EOT	end of transmission
005	005	005	0000 0101	ENQ	enquiry
006	006	006	0000 0110	ACK	acknowledgment
007	007	007	0000 0111	BEL	bell
008	010	008	0000 1000	BS	backspace
009	011	009	0000 1001	HT	horizontal tab
010	012	00A	0000 1010	LF	line feed
011	013	00B	0000 1011	VT	vertical tab
012	014	00C	0000 1100	FF	form feed
013	015	00D	0000 1101	CR	carriage return
014	016	00E	0000 1110	SO	shift out
015	017	00F	0000 1111	SI	shift in
016	020	010	0001 0000	DLE	data link escape
017	021	011	0001 0001	DC1	device control 1 (XON)
018	022	012	0001 0010	DC2	device control 2
019	023	013	0001 0011	DC3	device control 3 (XOFF)
020	024	014	0001 0100	DC4	device control 4
021	025	015	0001 0101	NAK	negative acknowledgement
022	026	016	0001 0110	SYN	synchronous idle
023	027	017	0001 0111	ETB	end of transmission block
024	030	018	0001 1000	CAN	cancel
025	031	019	0001 1001	EM	end of medium
026	032	01A	0001 1010	SUB	substitute
027	033	01B	0001 1011	ESC	escape
028	034	01C	0001 1100	FS	file separator
029	035	01D	0001 1101	GS	group separator
030	036	01E	0001 1110	RS	request to send/record separator
031	037	01F	0001 1111	US	unit separator
032	040	020	0010 0000	SP	space
033	041	021	0010 0001	!	exclamation mark
034	042	022	0010 0010	"	double quote
035	043	023	0010 0011	#	number sign
036	044	024	0010 0100	$	dollar sign
037	045	025	0010 0101	%	percent
038	046	026	0010 0110	&	ampersand
039	047	027	0010 0111	'	single quote
040	050	028	0010 1000	(	left/opening parenthesis
041	051	029	0010 1001	)	right/closing parenthesis
042	052	02A	0010 1010	*	asterisk
043	053	02B	0010 1011	+	plus
044	054	02C	0010 1100	,	comma
045	055	02D	0010 1101	-	minus or dash
046	056	02E	0010 1110	.	dot
047	057	02F	0010 1111	/	forward slash
048	060	030	0011 0000	0
049	061	031	0011 0001	1
050	062	032	0011 0010	2
051	063	033	0011 0011	3
052	064	034	0011 0100	4
053	065	035	0011 0101	5
054	066	036	0011 0110	6
055	067	037	0011 0111	7
056	070	038	0011 1000	8
057	071	039	0011 1001	9
058	072	03A	0011 1010	:	colon
059	073	03B	0011 1011	;	semi-colon
060	074	03C	0011 1100	<	less than
061	075	03D	0011 1101	=	equal sign
062	076	03E	0011 1110	>	greater than
063	077	03F	0011 1111	?	question mark
064	100	040	0100 0000	@	"at" symbol
065	101	041	0100 0001	A
066	102	042	0100 0010	B
067	103	043	0100 0011	C
068	104	044	0100 0100	D
069	105	045	0100 0101	E
070	106	046	0100 0110	F
071	107	047	0100 0111	G
072	110	048	0100 1000	H
073	111	049	0100 1001	I
074	112	04A	0100 1010	J
075	113	04B	0100 1011	K
076	114	04C	0100 1100	L
077	115	04D	0100 1101	M
078	116	04E	0100 1110	N
079	117	04F	0100 1111	O
080	120	050	0101 0000	P
081	121	051	0101 0001	Q
082	122	052	0101 0010	R
083	123	053	0101 0011	S
084	124	054	0101 0100	T
085	125	055	0101 0101	U
086	126	056	0101 0110	V
087	127	057	0101 0111	W
088	130	058	0101 1000	X
089	131	059	0101 1001	Y
090	132	05A	0101 1010	Z
091	133	05B	0101 1011	[	left/opening bracket
092	134	05C	0101 1100	\	back slash
093	135	05D	0101 1101	]	right/closing bracket
094	136	05E	0101 1110	^	caret/circumflex
095	137	05F	0101 1111	_	underscore
096	140	060	0110 0000	`
097	141	061	0110 0001	a
098	142	062	0110 0010	b
099	143	063	0110 0011	c
100	144	064	0110 0100	d
101	145	065	0110 0101	e
102	146	066	0110 0110	f
103	147	067	0110 0111	g
104	150	068	0110 1000	h
105	151	069	0110 1001	i
106	152	06A	0110 1010	j
107	153	06B	0110 1011	k
108	154	06C	0110 1100	l
109	155	06D	0110 1101	m
110	156	06E	0110 1110	n
111	157	06F	0110 1111	o
112	160	070	0111 0000	p
113	161	071	0111 0001	q
114	162	072	0111 0010	r
115	163	073	0111 0011	s
116	164	074	0111 0100	t
117	165	075	0111 0101	u
118	166	076	0111 0110	v
119	167	077	0111 0111	w
120	170	078	0111 1000	x
121	171	079	0111 1001	y
122	172	07A	0111 1010	z
123	173	07B	0111 1011	{	left/opening brace
124	174	07C	0111 1100	|	vertical bar
125	175	07D	0111 1101	}	right/closing brace
126	176	07E	0111 1110	~	tilde
127	177	07F	0111 1111	DEL	delete

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