'Java Based Search Engine\r'

'ACKNOWLEDGMENT I point thanks and gratitude to Mr. …………………………………………H. O. D computer science department, ……………………………………………………College for his encouraging take refuse and focus in carrying give a manner the ask. I would akin to express gratitude and indebtedness to Mr……………………………………, for his valuable advice and guidance without which this project would non sp devastation a penny seen the light of the day. I thank Mr………………………………… , project guide , GSS for his insistence on good computer weapons platformmeing technique which assistanted us to design and develop a successful model of an Chatting Tool. Nam e CONTENTS 1.STUDY & compendium PHASE 1. 1 psychiatric hospital 1. 1. 1 tar subscribe OF THE labor 1. 1. 2 PROBLEM IN lively corpse 1. 1. 3 SOLUTION OF THESE PROBLEMS 1. 1. 4 mountain chain OF THE labour 1. 1. 5 LIMITATIONS 1. 1. 6 HARDWARE & collect SPECIFICATIONS 1. 1. 7 ORGANISATION PROFILE 2. PROJECT compendium 1. STUDY OF THE SYSTEM 2. INPUT & output signal 3. motion mental facultyS deed WITH JUSTIFICATION 3. DESIGN PHASE 1. entropyFLOW 2. UML drawS 4. motionuation PHASE 5. shieldING 1. TYPES OF TESTING 1. COMPILING TEST 2. EXECUTION TEST 3. OUTPUT TEST 5. PROJECT CODING 6. OUTPUT SCREENS 7. CONCLUSION 8. BIBLOGRAPHYSTUDY PHASE INTRODUCTION: EXISTING SYSTEM With the advent of the Internet in the outgoing decade, inquiring for information in mixed formats has been rede comelyd by the internet lookup engines, intimately of them knowledge domain found on information retrieval (IR) rock techniques. IR-based huntinging, which usu all in all(prenominal) in ally allows formulation of queries with multiple rule books PROPOSED SYSTEM This Java activity is basically a recursive bill goer. You send packing search for files based on their file plant, their contents, or both in selected directory and as wellspring as sub directories of the specified directory.rail manner locomotive is a pictorial interlingual rendition of the well- cognise GREP utility, with an additional feature of traversing subdirectories. You aro consumption specify which directory to start looking in, which files to search finished, and what excogitation to look for in the files. The diverse fields confront tied(p) facial gestures, like Global busheledness Expression, ‘ locomotive’ has not sole(prenominal) the in writing(p) interface, hardly in both case a command- bloodline interface. This is partful for quick searches through, say, a breeding tree. Engine requires the Java 2 Platform, Standard mutation versio n 1. 4 or higher. SOLUTION OF THESE PROBLEMS in variable chemical formulas attri stille into all bods of school school text-manipulation tasks. fronting and search-and- stand in ar among the more than(prenominal)(prenominal) than commonality physical exercises, exclusively first- cosmic train expressions tramp also be use to test for certain conditions in a text file or info stream. You facultyiness use veritable(a) expressions, for precedent, as the basis for a short weapons platform that split ups next mail from incoming spam. In this case, the computer classme might use a unbroken expression to de terminal figureine whether the depict of a k at a timen spammer appe atomic itemize 18d in the â€Å"From:” line of the email. Email tense uping broadcasts, in fact, very often use mending expressions for just this type of operation. SCOPE OF THE PROJECTEngine is a graphical version of the well-kn take in GREP utility, with an additional feature of traversing subdirectories. The main aim of this project is to develop a java based recursive file reclaimer. Engine is a graphical version of the well-known GREP utility, with an additional feature of traversing subdirectories LIMITATIONS Regular expressions tend to be easier to relieve than they atomic number 18 to study. This is slight of a line if you be the only ane who ever motifs to maintain the broadcast (or sed routine, or shell script, or what fork up you), entirely if almost(prenominal) comm building blocky make to watch over it, the sentence structure mickle turn into more of a hitch than an aid.Ordinary macros (in occurrence, editable macros such as those generated by the major denomination processors and editors) tend not to be as fast, as flexible, as portable, as concise, or as fault-tolerant as timed expressions, still they deplete the advantage of macrocosm much more readable; final giveide people with no programming prickerground wha tsoever corporation usually make enough sense of a macro script to miscellany it if the essential arises. For approximately jobs, such readability for get outweigh all different concerns.As with all things in computing, its largely a question of fitting the creature to the job. HARDWARE & softw atomic number 18 SPECIFICATIONS Environment: Java Run cartridge holder Environment version 1. 4 or better installed. Operating System: both(prenominal) O. S. compatable with JVM Hard disk:10 GB mainframe:PIII or higher ORGANIZATION PROFILE towering SOFTWARE SOLUTIONS EMINENT TECHNOLOGIES (ET) is an IT Solution Provider for a dynamic environment w here business and applied science strategies converge.Our come along focuses on unfermented ways of business trust IT innovation and adoption spell also leverage an organizations current IT assets. We work with large orbiculate corporations and saucily generation engineering companies †to build refreshed products or ser vices and to implement prudent business and applied science strategies in at presents environment. EMINENTs throw of expertise embroils: Softwargon victimization Services Engineering Services Systems Integration guest Relationship focussing Supply Chain Management Product Development Electronic CommerceConsulting IT Outsourcing We apply technology with innovation and responsibility to achieve dickens bighearted objectives: Effectively address the business issues our customers face today Generate bleak opportunities that exit help them take a breather ahead in the future This rise rests on: A strategy where we Architect, Integrate and Manage technology services and solutions †we call it AIM for success. A blue offshore development methodological analysis and reduced look at on customer resources A focus on the use of reusable frameworks to brook cost and time benefitsWe combine the best people, processes and technology to achieve refined results consistently. We offer up customers the advantages of: Speed: We understand the instanteeance of timing, of getting in that location before the competition. A rich portfolio of reusable, modular frameworks helps jump start projects. Tried and tested methodology ensures that we follow a predictable, low-risk path to achieve results. Our rail record is testimony to interwoven projects delivered within and still before schedule. Expertise: Our teams combine cutting rim technology skills with rich domain expertise.Whats equally eventful †we sh atomic number 18 a strong customer predilection that gist we actually start by compensate to the customer. Were focused on coming up with solutions that give ear customer requirements today and anticipate future needs. A Full Service Portfolio: We offer customers the advantage of macrocosm able to Architect, Integrate and Manage technology services. This designates that they can rely on wholeness, fully responsible source or else of fork overing to integrate disparate multi-vendor solutions. Services: GSS is providing its services to Sain medicaments Pvt.Ltd, Grace drugs and pharmaceuticals Private particular Alka Drugs and Pharmaceuticals Pvt Ltd to name just a hardly a(prenominal) with out rich experience and expertise in selective information Technology we are in the best impersonate to provide software solutions to distinct business requirements. PROJECT ANALYSIS STUDY OF THE SYSTEM This application can be mainly divided into two modules:- • exploiter Interface • File Manipulation and filtering INPUT AND OUTPUT: User has to input the File Name or File Contents and he has to select the pound or Directory in which searching has to be d nonpareil.Application will search for the files coordinated with given criteria and shows the output in the text area of the application. PROCESS MODEL USED WITH JUSTIFICTION The model used here is a lock MODEL. This Model demands a direct go outation of practi ced risk at all stages of the project and if decently applied it reduces risk before they become problematic, hence it becomes easier to cut through a project when utilise this kind of model where in the end user can evaluate the program at the end of apiece stage and suggest modification if required.PROJECT DESIGN DATA FLOW DIAGRAM 0th take 1st Level 2nd Level 2nd Level tertiary Level UML DIAGRAMS USE CASE DIAGRAM [pic] year DIAGRAM [pic] ACTIVITY DIAGRAM [pic] SEQUENCE DIAGRAM [pic] IMPLEMENTATION PHASE mental facultyS: 1. COMPONENT THIS IS THE FRONT final stage CONSOLE OF THE USER TO INTERACT WITH SEARCH ANALYZER. 2. TOOLBAR COORDINATIOR THIS MODULE HAS THE EMBEDED TOOLS WHICH ARE TO IMPLEMENT SEARCH. 3. MAP FINDER THIS MODULE IS MAPS THE SEARCH CORRESPONDING TO THE USERS QUERY. 4. energetic STATUS FINDERTHIS IS THE DYNAMIC MODULE WHICH GIVES THE STATUS OF THE SEARCH . 5. GREP composer GREP GENERATOR IS THE MAJOR MODULE ON WHICH THE SEARCH IS make BASED ON REGULAR EXPRESSIONS . OUTPUT SCREENS Engine view [pic] Browse [pic] essay [pic] Help [pic] fault [pic] PROJECT CODING CODE EXPLANATION Regular expressions simplify example- jibing reckon Discover the elegance of uniform expressions in text-processing scenarios that involve pattern snatching schoolbook processing often involves matching text against a pattern.Although Javas nature and assorted string ground leveles offer subordinate pattern-matching support, that support commonly leads to complex code. To help you compile simpler pattern-matching code, Java provides well-ordered expressions with java. util. regex software program. Text processing much requires code to match text against patterns. That capability makes practicable text searches, email header validation, custom text creation from generic text (e. g. , â€Å"Dear Mr. Chakradhar” instead of â€Å"Dear Customer”), and so on. Java supports pattern matching via its acknowledgment and assorted string s omaes.Because that low-level support commonly leads to complex pattern-matching code, Java also offers stiff expressions to help you redeem simpler code. After introducing regular expression terminology, the java. util. regex piece of grounds classes, and a program that demonstrates regular expression constructs, I explore m individually of the regular expression constructs that the Pattern class supports. I also rise the methods comprising Pattern and different java. util. regex classes. A practical application of regular expressions concludes my discussion.Regular expressions long history begins in the hypothetical computer science fields of automata theory and noble spoken communication theory. That history continues to Unix and different operating systems, where regular expressions are often used in Unix and Unix-like utilities: examples include awk (a programming language that enables sophisticated text analysis and manipulation-named subsequently its creators, Aho, Weinberger, and Kernighan), emacs (a developers editor), and grep (a program that matches regular expressions in wizard or more text files and stands for global regular expression print).Regular expressions trace rearwards to the work of an American mathematician by the name of Stephen Kleene ( genius of the most influential bets in the development of theoretical computer science) who unquestionable regular expressions as a note for describing what he called â€Å"the algebra of regular sets. ” His work eventually found its way into slightly early efforts with computational search algorithms, and from there to some of the earliest text-manipulation official documents on the Unix platform (including ed and grep). In the context of computer searches, the â€Å"*” is formally known as a â€Å"Kleene star. â€Å"A regular expression, also known as a regex or regexp, is a string whose pattern (template) describes a set of draw. The pattern determines what strings belong to the set, and consists of literal characters and meta characters, characters that have special convey instead of a literal heart. The process of searching text to identify matchesâ€strings that match a regexs patternâ€is pattern matching. Javas java. util. regex package supports pattern matching via its Pattern, marriage broker, and PatternSyntaxException classes: 1. Pattern objects, also known as patterns, are compiled regexes 2.Matcher objects, or matchers, are engines that interpret patterns to locate matches in character sequences, objects whose classes implement the java. lang. CharSequence interface and serve as text sources 3. PatternSyntaxException objects describe illegal regex patterns Code for main pull aheaddow package jog. engine; conditional relation java. awt. *; momenteeee java. awt. event. *; outcome java. io. *; logical implication java. net. universal resource locator; import java. util. prefs. *; import java. util. regex. *; import javax. swi ng. *; import javax. swing. filechooser. FileFilter; import jog. engine. *; populace class MainWindow gallops JFrame implements ActionListener, File seekListener { rotected Preferences preferences; saved JTextField lookInField; protect JTextField filePatternField; protect JTextField searchForField; defend JTextField turn offField; defend JCheckBox includeSubCheckBox; defend JList resultList; defend RunSearch break offner; protect J barelyton browseButton; protected JButton helpButton; protected JButton startButton; protected JButton stopButton; protected JButton closeButton; protected JLabel office; protected JPanel cardPanel; protected CardLayout cardLayout; hush-hush boolean stopFlag; familiar MainWindow() { super(Bundle. get line(â€Å"AppTitle”)); addWindowListener( bracing WindowAdapter() humankind neutralise windowClosing(WindowEvent event) { handleClose(); } }); preferences = Preferences. userRoot(). node(â€Å"com/bluemarsh/jrgrep”); Container pane = getContentPane(); GridBagLayout gb = parvenuefangled GridBagLayout(); pane. setLayout(gb); GridBagConstraints gc = new GridBagConstraints(); gc. insets = new Insets(3, 3, 3, 3); JLabel enounce = new JLabel(Bundle. get ar trim(â€Å"lookInLabel”)); gc. lynchpin = GridBagConstraints. eastside; gb. setConstraints(label, gc); pane. add(label); trace s = preferences. get(â€Å"lookIn”, â€Å"”); lookInField = new JTextField(s, 20); gc. cast anchorperson = GridBagConstraints. western United States; gc. film = GridBagConstraints.HORIZONTAL; gc. weightx = 1. 0; gb. setConstraints(lookInField, gc); pane. add(lookInField); browseButton = new JButton(Bundle. get tie(â€Å"browseLabel”)); browseButton. addActionListener(this); gc. anchor = GridBagConstraints. union; gc. gridwidth = GridBagConstraints. sleep; gc. forgather = GridBagConstraints. n nonpareil; gc. weightx = 0. 0; gb. setConstraints(browseButton, gc); pane. add(browseButton); label = new JLabel(Bundle. get mountain chain(â€Å"filePatternLabel”)); gc. anchor = GridBagConstraints. eastward; gc. gridwidth = 1; gb. setConstraints(label, gc); pane. add(label); s = preferences. get(â€Å"filter”, â€Å"”); ilePatternField = new JTextField(s, 20); gc. anchor = GridBagConstraints. WEST; gc. fill = GridBagConstraints. HORIZONTAL; gc. gridwidth = GridBagConstraints. congeneric; gc. weightx = 1. 0; gb. setConstraints(filePatternField, gc); pane. add(filePatternField); Comp int gum tree = Box. createGlue(); gc. anchor = GridBagConstraints. CENTER; gc. fill = GridBagConstraints. NONE; gc. gridwidth = GridBagConstraints. equilibrium; gc. weightx = 0. 0; gb. setConstraints(glue, gc); pane. add(glue); label = new JLabel(Bundle. get throw off(â€Å"searchForLabel”)); gc. anchor = GridBagConstraints. EAST; gc. fill = GridBagConstraints.NONE; gc. gridwidth = 1; gb. setConstraints(label, gc); pane. add(label); s = preferences. get(â€Å"searchForà ¢â‚¬Â, â€Å"”); searchForField = new JTextField(s, 20); gc. anchor = GridBagConstraints. WEST; gc. fill = GridBagConstraints. HORIZONTAL; gc. gridwidth = GridBagConstraints. RELATIVE; gc. weightx = 1. 0; gb. setConstraints(searchForField, gc); pane. add(searchForField); helpButton = new JButton(Bundle. get power train(â€Å"helpLabel”)); helpButton. addActionListener(this); gc. anchor = GridBagConstraints. CENTER; gc. fill = GridBagConstraints. NONE; gc. gridwidth = GridBagConstraints. equilibrium; gc. weightx = 0. 0; gb. etConstraints(helpButton, gc); pane. add(helpButton); label = new JLabel(Bundle. get drawing string(â€Å" proveLabel”)); gc. anchor = GridBagConstraints. EAST; gc. gridwidth = 1; gb. setConstraints(label, gc); pane. add(label); s = preferences. get(â€Å"exclude”, â€Å"”); excludeField = new JTextField(s, 20); gc. anchor = GridBagConstraints. WEST; gc. fill = GridBagConstraints. HORIZONTAL; gc. gridwidth = GridBagConstraints. RELATIVE; gc. weightx = 1. 0; gb. setConstraints(excludeField, gc); pane. add(excludeField); glue = Box. createGlue(); gc. anchor = GridBagConstraints. CENTER; gc. fill = GridBagConstraints. NONE; gc. ridwidth = GridBagConstraints. REMAINDER; gc. weightx = 0. 0; gb. setConstraints(glue, gc); pane. add(glue); includeSubCheckBox = new JCheckBox( Bundle. getString(â€Å"includeSubDirLabel”), material(a)); includeSubCheckBox. setSelected(preferences. getBoolean( â€Å"recurse”, square(a))); gc. anchor = GridBagConstraints. WEST; gb. setConstraints(includeSubCheckBox, gc); pane. add(includeSubCheckBox); startButton = new JButton( Bundle. getString(â€Å"startSearchLabel”)); startButton. addActionListener(this); gc. gridwidth = 1; gb. setConstraints(startButton, gc); pane. add(startButton); status=new JLabel(â€Å"”); Color c=new Color(240,100,100); tatus. setForeground(c); gc. gridwidth = 1; gb. setConstraints(status, gc); pane. add(status); stopButton = n ew JButton(Bundle. getString(â€Å"stopLabel”)); stopButton. setEnabled( foolish); stopButton. addActionListener(this); gc. anchor = GridBagConstraints. CENTER; gc. gridwidth = GridBagConstraints. RELATIVE; gb. setConstraints(stopButton, gc); pane. add(stopButton); closeButton = new JButton(Bundle. getString(â€Å"closeLabel”)); closeButton. addActionListener(this); gc. gridwidth = GridBagConstraints. REMAINDER; gb. setConstraints(closeButton, gc); pane. add(closeButton); resultList = new JList(new ResultsListModel());JScrollPane scroller = new JScrollPane(resultList); cardPanel = new JPanel(new CardLayout()); cardLayout = (CardLayout) cardPanel. getLayout(); cardPanel. add(scroller, â€Å" angle of inclination”); gc. gridwidth = GridBagConstraints. REMAINDER; gc. grid aggrandisement = GridBagConstraints. REMAINDER; gc. fill = GridBagConstraints. BOTH; gc. weightx = 1. 0; gc. telltale(a) = 1. 0; gb. setConstraints(cardPanel, gc); pane. add(cardPanel); int width = preferences. getInt(â€Å"windowWidth”, 0); int height = preferences. getInt(â€Å"windowHeight”, 0); if (width == 0 && height == 0) { pack(); } else { setSize(width, height); } int top = preferences. getInt(â€Å"windowTop”, 100); nt left = preferences. getInt(â€Å"windowLeft”, 100); setLocation(left, top); stopFlag=false; } domain repress actionPerformed(ActionEvent event) { JButton furtherton = (JButton) event. getSource(); //System. out. println(â€Å"action â€Å"+button); if (button == closeButton) { handleClose(); } else if (button == browseButton) { handleBrowse(); } else if (button == startButton) { status. setText(â€Å"Search Started”); //System. out. println(â€Å"Search started”); startSearch(); } else if (button == helpButton) { displayHelp(); } else if (button == stopButton) { //System. out. println(â€Å"Search stopped”); stopButton. setEnabled(false); draw outner. stop(); stopFlag= full-strength; / int seem=((ListModel)resultList. getModel()). getSize(); //status. setText(â€Å"Search halt â€Å"+count+” Files Found”); } } protected head off displayHelp() { if (cardPanel. getComponentCount() < 2) { URL helpUrl = Bundle. getResource(â€Å"helpFile”); get rule book { JEditorPane editor = new JEditorPane(helpUrl); editor. setEditable(false); JScrollPane scroller = new JScrollPane(editor); cardPanel. add(scroller, â€Å"help”); } thumb (IOException ioe) { searchFailed(ioe); reproduction; } } cardLayout. show(cardPanel, â€Å"help”); } everyday vapidify fileFound(FileFoundEvent event) { ResultsListModel model = (ResultsListModel) resultList. etModel(); model. addElement(event. getFile()); } protected forfend handleBrowse() { String dirStr = lookInField. getText(); JFileChooser fc; if (dirStr. equals(â€Å"”)) { String lastdir = preferences. get(â€Å"lastdir”, visionary); if (lastdir == fruitless || lastdir. distance () == 0) { lastdir = System. getProperty(â€Å"user. dir”); } fc = new JFileChooser(lastdir); } else { fc = new JFileChooser(dirStr); } fc. setFileSelectionMode(JFileChooser. DIRECTORIES_ONLY); if (fc. showOpenDialog(this) ! = JFileChooser. CANCEL_OPTION) { File dir = fc. getSelectedFile(); String path = dir. getPath(); lookInField. setText(path); references. put(â€Å"lastdir”, path); } } protected annul handleClose() { preferences. putInt(â€Å"windowTop”, getY()); preferences. putInt(â€Å"windowLeft”, getX()); preferences. putInt(â€Å"windowWidth”, getWidth()); preferences. putInt(â€Å"windowHeight”, getHeight()); preferences. put(â€Å"lookIn”, lookInField. getText()); preferences. put(â€Å"filter”, filePatternField. getText()); preferences. put(â€Å"searchFor”, searchForField. getText()); preferences. put(â€Å"exclude”, excludeField. getText()); preferences. putBoolean(â€Å"recurse”, includeSub CheckBox. isSelected()); System. exit(0); } man neutralize searchComplete() { stopButton. etEnabled(false); //status. setText(â€Å"Search completed”); int count=((ListModel)resultList. getModel()). getSize(); if(count==0){ status. setText(â€Å"Search Completed No Files Found”); } if(stopFlag){ status. setText(â€Å"Search Stopped â€Å"+count +” Files Found”); stopFlag=false; }else{ status. setText(â€Å"Search Completed â€Å"+count +” Files Found”); } } macrocosm void searchFailed(Throwable t) { Object[] messages = {Bundle. getString(â€Å" overlookionOccurred”),t. getMessage()}; JOptionPane. showMessageDialog(this, messages, Bundle. getString(â€Å"errorTitle”), JOptionPane. ERROR_MESSAGE); } protected void startSearch() { cardLayout. how(cardPanel, â€Å" angle of inclination”); ResultsListModel model = (ResultsListModel) resultList. getModel(); model. clear(); String dirStr = lookInField. getText(); if (dirStr == vigour || dirStr. length() == 0) { dirStr = â€Å". â€Å"; } File dir = new File(dirStr); if (! dir. exists()) { JOptionPane. showMessageDialog(this, Bundle. getString(â€Å"pathDoesNotExist”), Bundle. getString(â€Å"errorTitle”), JOptionPane. ERROR_MESSAGE); damages; } String target = searchForField. getText(); String filter = filePatternField. getText(); String exclude = excludeField. getText(); try { Pattern. compile(target); Pattern. compile(filter); Pattern. ompile(exclude); } exigency (PatternSyntaxException pse) { Object[] messages = {Bundle. getString(â€Å"invalidRegexPattern”), pse. getMessage()}; JOptionPane. showMessageDialog(this, messages, Bundle. getString(â€Å"errorTitle”),JOptionPane. ERROR_MESSAGE); dedicate; } if (runner == null) { runner = new RunSearch(this); } runner. search(dir, target, filter, includeSubCheckBox. isSelected(), exclude); Thread th = new Thread(runner); th. start(); stopButton. setEnabled(true); } } Code for bundle package jog. engine; import java. net. URL; import java. util. MissingResourceException; import java. til. ResourceBundle; usual class Bundle { private nonmoving ResourceBundle resourceBundle; passive { resourceBundle = ResourceBundle. getBundle(Bundle. class. getName()); } public still ResourceBundle getBundle() { return resourceBundle; } public static URL getResource(String chance on) { String name = getString(key); return name == null ? null : Bundle. class. getResource(name); } public static String getString(String key) { try { return resourceBundle. getString(key); } catch (MissingResourceException mre) { return null; } } } Code for runsearch package jog. engine; import java. io. File; import jog. engine. *; mport java. lang. *; class RunSearch implements Runnable { protected File dir; protected String lookFor; protected String filter; protected boolean subDirs; protected String exclude; protected FileSearchListener listener; protected quester searcher; public RunSearch(FileSearchListener listener) { this. listener = listener; } public void run() { if (searcher == null) { searcher = new Searcher(); if (listener ! = null) { searcher. addSearchListener(listener); } } searcher. search(dir, lookFor, filter, subDirs, exclude); } public void search(File dir, String lookFor, String filter, boolean subDirs, String exclude) this. dir = dir; this. lookFor = lookFor; this. filter = filter; this. subDirs = subDirs; this. exclude = exclude; } public void stop() { //System. out. println(â€Å"Searcher is one:”+ isAlive()); System. out. println(â€Å"Searcher”); if (searcher ! = null) { searcher. stopSearching(); searcher=null; System. out. println(â€Å"Searcher one”); } //System. out. println(â€Å"Searcher is :”+ isAlive()); //System. out. println(â€Å"Searcher one”); } } Code for searcher package jog. engine; import java. io. *; import java. nio. *; import java. nio. channels. *; import java. nio. charset. *; impo rt java. util. *; import java. til. regex. *; import javax. swing. event. EventListenerList; import jog. engine. *; class Searcher { protected static Pattern linePattern; protected static Charset charset; protected static CharsetDecoder decoder; protected EventListenerList searchListeners; protected erratic boolean stopSearch; protected Pattern targetPattern; protected Matcher targetMatcher; protected Pattern filterPattern; protected Matcher filterMatcher; protected Pattern excludePattern; protected Matcher excludeMatcher; static { try { linePattern = Pattern. compile(â€Å". * ? â€Å"); } catch (PatternSyntaxException pse) { System. out. rintln(â€Å"Ye flipping gods! â€Å"); } charset = Charset. forName(â€Å"ISO-8859-1”); decoder = charset. newDecoder(); } public Searcher() { searchListeners = new EventListenerList(); } public void addSearchListener(FileSearchListener listener) { searchListeners. add(FileSearchListener. class, listener); } protected void fireDone() { if (searchListeners == null) { return; } Object[] listeners = searchListeners. getListenerList(); for (int i = listeners. length †2; i >= 0; i -= 2) { if (listeners[i] == FileSearchListener. class) { FileSearchListener fsl = (FileSearchListener) listeners[i + 1]; fsl. earchComplete(); } } } protected void fireError(Throwable t) { if (searchListeners == null) { return; } Object[] listeners = searchListeners. getListenerList(); for (int i = listeners. length †2; i >= 0; i -= 2) { if (listeners[i] == FileSearchListener. class) { FileSearchListener fsl = (FileSearchListener) listeners[i + 1]; fsl. searchFailed(t); } } } protected void fireFound(String match) { if (searchListeners == null) { return; } FileFoundEvent event = new FileFoundEvent(this, match); Object[] listeners = searchListeners. getListenerList(); for (int i = listeners. ength †2; i >= 0; i -= 2) { if (listeners[i] == FileSearchListener. class) { FileSearchListener fsl = (FileSearchListener) liste ners[i + 1]; fsl. fileFound(event); } } event = null; } public void removeSearchListener(FileSearchListener listener) { searchListeners. remove(FileSearchListener. class, listener); } public void search(File startIn, String target, String filter, boolean recurse, String exclude) { stopSearch = false; try { targetPattern = Pattern. compile(target); filterPattern = Pattern. compile(filter); if (exclude ! = null && exclude. length() > 0) { excludePattern = Pattern. ompile(exclude); } searchLow(startIn, recurse); } catch (IOException ioe) { fireError(ioe); } catch (PatternSyntaxException pse) { fireError(pse); } targetPattern = null; targetMatcher = null; filterPattern = null; filterMatcher = null; excludePattern = null; excludeMatcher = null; fireDone(); } protected void searchLow(File startIn, boolean recurse) throws IOException { String[] files = startIn. list(); if (files == null) { return; } for (int ii = 0; ii < files. length; ii++) { if (stopSearch) { discriminat e; } File file = new File(startIn, files[ii]); if (file. isFile() && file. canRead()) { String file name = file. etCanonicalPath(); if (filterMatcher == null) { filterMatcher = filterPattern. matcher( computer file name); } else { filterMatcher. reset(filename); } if (! filterMatcher. discern()) { continue; } FileInputStream fis = new FileInputStream(file); FileChannel fc = fis. getChannel(); MappedByteBuffer bb = fc. map(FileChannel. MapMode. READ_ONLY, 0, fc. size()); CharBuffer cb = decoder. decode(bb); boolean matchFound = false; if ((targetPattern. flags() & Pattern. DOTALL) ! = 0) { if (targetMatcher == null) { targetMatcher = targetPattern. matcher(cb); } else { argetMatcher. reset(cb); } if (targetMatcher. find()) { matchFound = true; } } else { Matcher lm = linePattern. matcher(cb); while (lm. find()) { CharSequence cs = lm. group(); if (targetMatcher == null) { targetMatcher = targetPattern. matcher(cs); } else { targetMatcher. reset(cs); } if (targetMatch er. find()) { matchFound = true; } if (lm. end() == cb. limit()) { break; } } } if (matchFound) { fireFound(filename); } } else if (recurse && file. isDirectory()) { String dirname = file. getName(); if (excludePattern ! = null) { if (excludeMatcher == null) { excludeMatcher = excludePattern. atcher(dirname); } else { excludeMatcher. reset(dirname); } if (! excludeMatcher. find()) { searchLow(file, recurse); } } else { searchLow(file, recurse); } } } } public void stopSearching() { stopSearch = true; } } Code for filesearch listener package jog. engine; import java. util. EventListener; import jog. engine. FileFoundEvent; interface FileSearchListener extends EventListener { public void fileFound(FileFoundEvent event); public void searchComplete(); public void searchFailed(Throwable t); } Code for tty package jog. engine; import java. io. *; import java. util. regex. *; mport jog. engine. *; public class tty implements FileSearchListener { protected static int argIndex; pro tected static String excludeStr = â€Å"”; protected static String nameStr = â€Å"”; protected static void displayHelp() { String str = Bundle. getString(â€Å"ttyHelp1”); int i = 1; while (str ! = null) { System. out. println(str); i++; str = Bundle. getString(â€Å"ttyHelp” + i); } } public void fileFound(FileFoundEvent event) { System. out. println(event. getFile()); } protected static boolean processArgs(String[] args) { while (argIndex < args. length) { String arg = args[argIndex]; if (arg. equals(â€Å"-exclude”)) { rgIndex++; excludeStr = args[argIndex]; } else if (arg. equals(â€Å"-h”) || arg. equals(â€Å"-help”) || arg. equals(â€Å"â€help”)) { displayHelp(); return false; } else if (arg. equals(â€Å"-name”)) { argIndex++; nameStr = args[argIndex]; } else { break; } argIndex++; } return true; } public void searchComplete() {} public void searchFailed(Throwable t) { System. err. println(Bundle. getStrin g(â€Å"exceptionOccurred”)); System. err. println(t. getMessage()); } public static void main(String[] args) { try { if (! processArgs(args)) { return; } } catch (ArrayIndexOutOfBoundsException aioobe) { System. err. println(Bundle. etString(â€Å"ttyMissingArguments”)); return; } if (argIndex == args. length) { System. err. println(Bundle. getString(â€Å"ttyMissingRequired”)); return; } String target = args[argIndex]; argIndex++; String dirStr = null; if (argIndex == args. length) { dirStr = â€Å". â€Å"; } else { dirStr = args[argIndex]; } File dir = new File(dirStr); if (! dir. exists()) { System. err. println(Bundle. getString(â€Å"pathDoesNotExist”)); return; } try { Pattern. compile(target); Pattern. compile(nameStr); } catch (PatternSyntaxException pse) { System. err. println(Bundle. getString(â€Å"invalidRegexPattern”)); System. rr. println(pse. getMessage()); return; } Searcher searcher = new Searcher(); tty precedent = new tty(); searcher. addSearchListener(instance); searcher. search(dir, target, nameStr, true, excludeStr); searcher. removeSearchListener(instance); } } Code for filefoundevent package jog. engine; import java. util. EventObject; class FileFoundEvent extends EventObject { protected String file; public FileFoundEvent(Object source, String file) { super(source); this. file = file; } public String getFile() { return file; } } Code for result list model package jog. engine; import java. util. vector; import javax. wing. AbstractListModel; import jog. engine. *; class ResultsListModel extends AbstractListModel { protected sender list entropy; public ResultsListModel() { listData = new Vector(); } public void addElement(Object o) { listData. add(o); fireIntervalAdded(this, listData. size(), listData. size()); } public void clear() { int size = listData. size(); listData. clear(); fireIntervalRemoved(this, 0, size); } public Object getElementAt(int i) { try { return listData. elementAt(i); } catc h (ArrayIndexOutOfBoundsException e) { return null; } } public int getSize() { return listData. size(); } } Code for main package jog. ngine; import jog. engine. *; public class Main { public static void main(String[] args) { new MainWindow(). show(); // new jog. searchdesk. MainWindow. show(); } } For a musical instrument with full regex support, metacharacters like â€Å"*” and â€Å"? ” (or â€Å"wildcard operators,” as they are some measure called) are only the tip of the iceberg. Using a good regex engine and a well-crafted regular expression, one can slow search through a text file (or a hundred text files) searching for pronounces that have the suffix â€Å". hypertext markup language” (but only if the discourse begins with a capital earn and occurs at the commencement of the line), deputize the . tml suffix with a . monetary standard generalized markup language suffix, and thence change all the trim cover case characters to upper case. Wi th the right tools, this series of regular expressions would do just that: s/(^[A_Z]{1})([a-z]+). sgml/12. html/g tr/a-z/A-Z/ As you might opine from this example, concision is everything when it comes to crafting regular expressions, and while this syntax wont win every(prenominal) beauty prizes, it follows a logical and more or less standardized format which you can learn to rea+*d and write easily with just a microscopical bit of practice. In a regular expression, everything is a generalized pattern.If I type the word â€Å"serendipitous” into my editor, Ive created one instance of the word â€Å"serendipitous. ” If, however, I bespeak to my tool (or compiler, or editor, or what have you) that Im now typing a regular expression, I am in effect creating a template that matches all instances of the characters â€Å"s,” â€Å"e,” â€Å"r,” â€Å"e,” â€Å"n,” â€Å"d,” â€Å"i,” â€Å"p,” â€Å"i,” â⠂¬Å"t,” â€Å"o,” â€Å"u,” and â€Å"s” all in a row. The standard way to find â€Å"serendipitous” (the word) in a file is to use â€Å"serendipitous” (the regular expression) with a tool like egrep (or extended grep): $ egrep â€Å"serendipitous” foobar ;hitsThis line, as you might guess, asks egrep to find instances of the pattern â€Å"serendipitous” in the file â€Å"foobar” and write the results to a file called â€Å"hits”. In the forward examples, we have been using regular expressions that cleave to the first rule of regular expressions: namely, that all alphameric characters match themselves. There are other characters, however, that match in a more generalized fashion. These are usually referred to as the meta characters. Some meta characters match hit characters. This includes the following symbols: . Matches every one character …]Matches both character listed surrounded by the brackets [^â €¦]Matches any character except those listed in the midst of the brackets aver we have a measuring of filenames listed out in a file called â€Å"Important. files. ” We pauperization to â€Å"grep out” those filenames which follow the pattern â€Å"blurfle1”, â€Å"blurfle2”, â€Å"blurfle3,” and so on, but exclude files of the form â€Å"1blurfle”, â€Å"2blurfle”, â€Å"3blurfle” The following regex would do the delusion: $ egrep â€Å"blurfle. ” Important. files ;blurfles The authoritative thing to realize here is that this line will not match merely the string â€Å"blurfle. (that is, â€Å"blurfle” followed by a period). In a regular expression, the dot is a reserved symbol (well get to matching periods a little further on). This is fine if we arent particular about the character we match (whether its a â€Å"1,” a â€Å"2,” or even a letter, a space, or an underscore). Narrowing the f ield of choices for a genius character match, however, requires that we use a character class. portion classes match any character listed within that class and are separated off using square brackets.So, for example, if we commanded to match on â€Å"blurfle” but only when it is followed immediately by a number (including â€Å"blurfle1” but not â€Å"blurflez”) we would use something like this: $ egrep â€Å"blurfle[0123456789]” Important. files >blurfles The syntax here is just as it seems: â€Å"Find ‘blurfle followed by a secret code, a one, a two, a three, a four, a five, a six, a seven, an eight, or a nine-spot. ” such(prenominal) classes are usually abbreviated using the range operator (â€Å"-â€Å"): $ egrep â€Å"blurfle[0-9]” Important. files >blurfles The following regex would find â€Å"blurfle” followed by any alphanumeric character (upper or lower case). egrep â€Å"blurfle[0-9A-Za-z]” Importan t. files >blurfles (Notice that we didnt write blurfle[0-9 A-Z a-z] for that last one. The spaces might make it easier to read, but wed be matching on anything between cipher and nine, anything between a and z, anything between A and Z, or a space. ) A carat at the beginning of the character class negates that class. In other lecture, if you requireed to find all instances of blurfle except those which end in a number, youd use the following: $ egrep â€Å"blurfle[^0-9]” Important. files >blurfles Many regex implementations have â€Å"macros” for various character classes.In Perl, for example, d matches any dactyl ([0-9]) and w matches any â€Å"word character” ([a-zA-Z0-9_]). Grep uses a meagerly different notation for the similar thing: [:digit:] for digits and [:alnum:] for alphanumeric characters. The man page (or other documentation) for the particular tool should list all the regex macros available for that tool. Quantifiers The regular expressi on syntax also provides metacharacters which specify the number of measure a particular character should match. ?Matches any character zero or one times *Matches the preceding element zero or more times +Matches the preceding element one or more times num}Matches the preceding element num times {min, sludge}Matches the preceding element at to the lowest degree min times, but not more than max times These metacharacters allow you to match on a exclusive-character pattern, but then continue to match on it until the pattern changes. In the last example, we were trying to search for patterns that contain â€Å"blurfle” followed by a number between zero and nine. The regex we came up with would match on blurfle1, blurfle2, blurfle3, and so forth If, however, you had a programmer who mistakenly thought that â€Å"blurfle” was sibyllic to be spelled â€Å"blurffle,” our regex wouldnt be able to catch it.We could fix it, though, with a quantifier. $ egrep â€Å"b lur[f]+le[0-9]” Important. files >blurfles Here we have â€Å"Find ‘b, ‘l, ‘u, ‘r (in a row) followed by one or more instances of an ‘f followed by ‘l and ‘e and then any single digit character between zero and nine. ” Theres always more than one way to do it with regular expressions, and in fact, if we use single-character metacharacters and quantifiers in conjunction with one other, we can search for almost all the variant spellings of â€Å"blurfle” (â€Å"bllurfle,” â€Å"bllurrfle”, bbluuuuurrrfffllle”, and so on).One way, for example, might employ the ubiquitous (and exceedingly powerful) . * combination: $ egrep â€Å"b. *e” Important. files ;blurfles If we work this out, we come out with something like: â€Å"find a ‘b followed by any character any number of times (including zero times) followed by an ‘e. ” Its enticing to use â€Å". *” with abandon. Howev er, bear in mind that the preceding example would match on words like â€Å"blue” and â€Å"baritone” as well as â€Å"blurfle. ” Suppose the filenames in blurfle are numbered up to 12324, but we only care about the first 999: $ egrep â€Å"blurfle[0-9]{3}” Important. files >bluflesThis regex tells egrep to match any number between zero and nine exactly three times in a row. Similarly, â€Å"blurfle[0-9]{3,5}” matches any number between zero and nine at lest three times but not more than five times in a row. Anchors Often, you need to specify the position at which a particular pattern occurs. This is often referred to as â€Å"anchoring” the pattern: ^Matches at the start of the line $Matches at the end of the line <Matches at the beginning of a word >Matches at the end of a word Matches at the beginning or the end of a word BMatches any charater not at the beginning or end of a word ^” and â€Å"$” are some of the mos t useful metacharacters in the regex arsenalâ€particularly when you need to run a search-and-replace on a list of strings. Suppose, for example, that we want to take the â€Å"blurfle” files listed in Important. files, list them out separately, run a program called â€Å"fragellate” on separately one, and then append each successive output to a file called â€Å"fraggled_files. ” We could write a full-blown shell script (or Perl script) that would do this, but often, the job is faster and easier if we build a very simple shell script with a series of regular expressions.Wed begin by greping the files we want to operate on and writing the output to a file. $ egrep â€Å"blurfle[0-9]” Important. file ;script. sh This would give us a list of files in script. sh that looked something like this: blurfle1 blurfle2 blurfle3 blurfle4 . . . Now we use sed (or the â€Å"/%s” operator in vi, or the â€Å"query-replace-regexp” command in emacs) to p ut â€Å"fragellate” in front of each filename and â€Å">>fraggled_files” after each filename. This requires two separate search-and-replace trading operations (though not necessarily, as Ill explain when we get to backreferences).With sed, you have the ability to put both substitution lines into a file, and then use that file to iterate through another making each substitution in turn. In other words, we create a file called â€Å"fraggle. sed” which contains the following lines: s/^/fraggelate / s/$/ >>fraggled_files/ Then run the following â€Å"sed routine” on script. sh like so: $ sed -f fraggle. sed script. sh >script2. sh Our script would then look like this: fraggelate blurfle1 >>fraggled_files fraggelate blurfle2 >>fraggled_files fraggelate blurfle3 >>fraggled_files raggelate blurfle4 >>fraggled_files . . Chmod it, run it, and youre done. Of course, this is a somewhat trivial example (â€Å" wherefore wou ldnt you just run â€Å"fragglate blurfle* ;;fraggled_files” from the command line? â€Å"). Still, one can easily imagine instances where the criteria for the file name list is too complicated to express using [filename]* on the command line. In fact, you can in all probability see from this sed-routine example that we have the makings of an automatic shell-script generator or file filter. You may also have noticed something odd about that caret in our sed routine.Why doesnt it mean â€Å"except” as in our previous example? The answer has to do with the sometimes radical residuum between what an operator doer inside the range operator and what it means outside it. The rules change from tool to tool, but generally speaking, you should use metacharacters inside range operators with caution. Some tools dont allow them at all, and others change the meaning. To survival of the fittest but one example, most tools would interpret [A-Za-z. ] as â€Å"Any character betw een A and Z, a and z or a period. ” Most tools provide some way to anchor a match on a word boundary.In some versions of grep, for example, you are allowed to write: $ grep â€Å"fle>” Important. files ;blurfles This says: â€Å"Find the characters â€Å"f”, â€Å"l”, â€Å"e”, but only when they come at the end of a word. ”  tells the regex engine to match any word boundary (whether its at the beginning or the end) and B tells it to match any position that isnt a word boundary. This again can vary considerably from tool to tool. Some tools dont support word boundaries at all, and others support them using a slightly different syntax.The tools that do support word boundaries generally consider words to be bounded by spaces or punctuation, and consider numerals to be legitimate parts of words, but there are some variations on these rules that can effect the accuracy of your matches. The man page or other documentation should resolve the ma tter. Escape Characters By now, youre believably wondering how you go about searching for one of the special characters (asterisks, periods, slashes, and so on). The answer lies in the use of the miss characterâ€for most tools, the backslash (â€Å"”).To reverse the meaning of a special character (in other words, to embrace it as a normal character instead of as a metacharacter), we only when put a backslash before that character. So, we know that a regex like â€Å". *” finds any character any number of times. But conceive of were searching for ellipses of various lengths and we just want to find periods any number of times. Because the period is normally a special character, wed need to escape it with a backslash: $ grep â€Å". *” Important. Files ;ellipses. files Unfortunately, this domiciliate to the legendary ugliness of regular expressions more than any other element of the syntax.Add a few escape characters, and a simple sed routine designed to replace a couple of URLs quickly degenerates into confusion: sed ‘s/http://etext. lib. virginia. edu//http://www. etext. virginia. edu/g To make matters worse, the list of what needs to be escaped differs from tool to tool. Some tools, for example, consider the â€Å"+” quantifier to have its normal meaning (as a unexceptional plus sign) until it is escaped. If youre having trouble with a regex (a sed routine that wont dissect or a grep pattern that wont match even though youre certain the pattern exists), try play around with the escapes.Or better yet, read the man page. Alternation Alternation refers to the use of the â€Å"|” symbol to indicate logical OR. In a previous example, we used â€Å"blur[f]+le” to catch those instances of â€Å"blurfle” that were misspelled with two â€Å"fs”. Using alternation, we could have written: $ egrep â€Å"blurfle|blurffle” Important. files ;blurfles This means simply â€Å"Find either blurfle OR blurffle. ” The power of this becomes more evident when we use parentheses to limit the mountain range of the secondary matches.Consider the following regex, which accounts for both the American and British spellings of the word â€Å"gray”: $ egrep â€Å"gr(a|e)y” Important. files ;hazy. shades Or perhaps a mail-filtering program that uses the following regex to single out past correspondence between you and the boss: /(^To:|^From:) (Seaman|Ramsay)/ This says, â€Å"Find a ‘To: or a ‘From: line followed by a space and then either the word ‘Seaman or the word ‘Ramsay This can make your regexs extremely flexible, but be careful! Parentheses are also meta characters which figure prominently in the use of . . . Back referencesPerhaps the most powerful element of the regular expression syntax, back references allows you to load the results of a matched pattern into a modify and then reuse it later in the expression. In a previous examp le, we used two separate regular expressions to put something before and after a filename in a list of files. I mentioned at that point that it wasnt entirely necessary that we use two lines. This is because back references allow us to get it down to one line. Heres how: s/(blurfle[0-9]+)/fraggelate 1 >>fraggled_files/ The key elements in this example are the parentheses and the â€Å"1”.Earlier we observe that parentheses can be used to limit the scope of a match. They can also be used to save a particular pattern into a temporary fender. In this example, everything in the â€Å"search” one-half of the sed routine (the â€Å"blurfle” part) is saved into a buffer. In the â€Å"replace” half we recall the contents of that buffer back into the string by referring to its buffer number. In this case, buffer â€Å"1”. So, this sed routine will do just what the earlier one did: find all the instances of blurfle followed by a number between zero an d nine and replace it with â€Å"fragellate blurfle[some number] ;;fraggled files”.Backreferences allow for something that very few indifferent search engines can manage; namely, strings of info that change slightly from instance to instance. rascal total schemes provide a perfect example of this. Suppose we had a document that numbered each page with the notation . The number and the chapter name change from page to page, but the rest of the string stays the same. We can easily write a regular expression that matches on this string, but what if we wanted to match on it and then replace everything but the number and the chapter name? //Page 1, Chapter 2/ Buffer number one (â€Å"1”) holds the first matched sequence, ([0-9]+); buffer number two (â€Å"2”) holds the second, ([A-Za-z]+). Tools vary in the number of backreference they can hold. The more common tools (like sed and grep) hold nine, but Python can hold up to ninety-nine. Perl is limited only by the amount of physical memory (which, for all practical purposes, means you can have as numerous as you want). Perl also lets you assign the buffer number to an ordinary scalar variable ($1, $2, etc. ) so you can use it later on in the code block. a.OBJECT ORIENTED PROGRAMMING AND JAVA Object-oriented Programming was developed because of limitations found in earlier approaches of programming. To appreciate what OOP does, we need to understand what these limitations are and how they arose from traditional programming. PROCEDURAL LANGUAGES Pascal, C, Basic, FORTRAN, and uniform languages are procedural languages. That is, each statement in the language tells the computer to do something: Get some input, add these numbers, divide by 6, display the output. A program in a procedural language is a list of instructions.For very small programs no other organizing principle (often called a paradigm) is needed. The programmer creates the list of instructions, and the computer carries them out. Division into Functions When programs become larger, a single list of instructions becomes unwieldy. Few programmers can comprehend a program of more than a few hundred statements unless it is broken down into smaller units. For this condition the contribution was adopted as a way to make programs more comprehensible to their human creators. (The term functions is used in C++ and C.In other languages the same concept may be referred to as a subroutine, a subprogram, or a procedure. ) A program is divided into functions, and ( imaginationlly, at least) each function has a understandably defined purpose and a clearly defined interface to the other functions in the program. The paper of breaking a program into functions can be further extended by grouping a number of functions together into a larger entity called a module, but the principle is similar: grouping a number of components that carry out specific tasks.Dividing a program into functions and modules is one of the cornersto nes of structured programming, the somewhat loosely defined discipline that has influenced programming organization for more than a decade. Problems with Structured Programming As programs turn ever larger and more complex, even the structured programming approach begins to show signs of strain. You may have heard about, or been involved in, horror stories of program development. The project is too complex, the schedule slips, more programmers are added, complexity increases, costs skyrocket, the schedule slips further, and disaster ensues.Analyzing the reasons for these chastenings reveals that there are weaknesses in the procedural paradigm itself. No matter how well the structured programming approach is implemented, large programs become excessively complex. What are the reasons for this failure of procedural languages? One of the most crucial is the subroutine played by selective information. Data Under setd In a procedural language, the emphasis is on doing thingsâ€rea d the keyboard, change the vector, check for errors, and so on. The subdivision of a program into functions continues this emphasis. Functions do things just as single program statements do.What they do may be more complex or abstract, but the emphasis is still on the action. What happens to the data in this paradigm? Data is, after all, the reason for a programs existence. The important part of an enumeration program isnt a function that displays the data, or a function that checks for correct input; its the livestock data itself. Yet data is given second-class status in the organization of procedural languages. For example, in an inventory program, the data that makes up the inventory is probably read from a disk file into memory, where it is treated as a global variable.By global we mean that the variables that form the data are declared outside of any function, so they are rileible to all functions. These functions do various operations on the data. They read it, dissect it, update it, rearrange it, display it, write it back to the disk, and so on. We should note that most languages, such as Pascal and C, also support topical anaesthetic variables, which are hidden within a single function. But local variables are not useful for important data that essential be plan of attacked by many different functions. Now suppose a new programmer is hired to write a function to analyze this nventory data in a certain way. Unfamiliar with the subtleties of the program, the programmer creates a function that by chance corrupts the. This is easy to do, because every function has complete devil to the data. Its like leaving your personal papers in the lobby of your apartment building: Anyone can change or destroy them. In the same way, global data can be corrupted by functions that have no business changing it. another(prenominal) problem is that, since many functions access the same data, the way the data is stored becomes critical.The arrangement of the data cant be changed without modifying all the functions that access it. If you add new data items, for example, youll need to modify all the functions that access the data so that they can also access these new items. It will be hard to find all such functions, and even harder to modify all of them correctly. Its similar to what happens when your local supermarket moves the bread from aisle 4 to aisle 12. Everyone who patronizes the supermarket must figure out where the bread has gone, and adjust their shop habits accordingly.What is needed is a way to restrict access to the data, to hide it from all but a few critical functions. This will protect the data, simplify maintenance, and offer other benefits as well. Relationship to the Real creation Procedural programs are often difficult to design. The problem is that their chief componentsâ€functions and data structuresâ€dont model the real world very well. For example, suppose you are writing a program to create the elements of a graphics user interface: menus, windows, and so on. Quick now, what functions will you need? What data structures?The answers are not obvious, to say the least. It would be better if windows and menus corresponded more closely to actual program elements. New Data Types There are other problems with traditional languages. One is the difficulty of creating new data types. Computer languages typically have several intact data types: integers, floating-point numbers, characters, and so on. What if you want to invent your own data type? Perhaps you want to work with complex numbers, or two dimensional coordinates, or datesâ€quantities the built-in data types don’t handle easily.Being able to create your own types is called extensibility; you can extend the capabilities of the language. Traditional languages are not usually extensible. Without stirred convolutions, you can’t bundle together both X and Y coordinates into a single variable called Point, and then add and s ubtract surveys of this type. The result is that traditional programs are more complex to write and maintain. The object oriented approach The fundamental idea behind object-oriented languages is to combine into a single unit both data and the functions that operate on that data.Such a unit is called an object. An object’s functions, called member methods in Java, typically provide the only way to access its data. If you want to read the item and return the value to you, you call a member function in the object. It will read the item and return the value to you. You can’t access the data directly. The data is hidden, so it is safe from accidental modification. Data and its functions are said to be encapsulated into a single entity. Data encapsulation and data hiding are key basis in the description of object oriented languages.If you want to modify the data in an object, you know exactly what functions interact with it: the member functions in the object. No other fu nctions can access the data. This simplifies writing, debugging, and maintaining the program. A Java program typically consists of a number of objects, which communicate with each other by calling one another’s members functions. We should mention that what are called member functions in C++ are called methods in Java. Also, data items are referred to as instance variables. Calling an object’s member function is referred to as sending a message to the object.\r\n'