FAKULTÄT FÜR INFORMATIK

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1 TECHNISCHE UNIVERSITÄT MÜNCHEN FAKULTÄT FÜR INFORMATIK Lehrstuhl für Sprachen und Beschreibungsstrukturen WS 2007/2008 Praktikum Grundlagen der Programmierung Lösungsvorschläge zu Blatt 10 F. Forster, T. Gawlitza, A. Flexeder Übungen zu Praktikum Grundlagen der Programmierung Aufgabe 46 (Ü) Ausnahmen a) public class FalschesFormatException extends Exception { private int wortnummer ; public FalschesFormatException (int wn) { wortnummer = wn; public String tostring () { return " FalschesFormatException : Wort " + wortnummer ; b) public class Aufgabe { public static int berechnewert ( String datei) throws FalschesFormatException, DateiNichtVorhandenException { int erg = 0; DateiLeser l = new DateiLeser ( datei ); String token = null; boolean operand = true; int wort = 1; while (( token = l. lesenaechsteswort ())!= null) { if (operand) { int zahl; zahl = Integer. parseint ( token ); catch ( NumberFormatException ex) { throw new FalschesFormatException ( wort ); erg += zahl; { if (! token.equals("+")) throw new FalschesFormatException ( wort ); wort ++; operand =! operand; if ( operand) throw new FalschesFormatException ( wort ); return erg; public static void main( String [] args) throws Exception { System. out. println( berechnewert (" test. rechnung "));

2 Lösung 10/ Seite 2 Aufgabe 47 Terminkalender (Lösungsvorschlag) import java. util.*; public class Converter { private static final int[] monattage = new int[]{31,28,31,30,31,30,31,31,30,31,30,31; private static final int[] monattages = new int[]{31,29,31,30,31,30,31,31,30,31,30,31; public static int convertzeit ( String zeit) throws DatumsformatException { zeit = zeit. trim (); StringTokenizer to = new StringTokenizer ( zeit, ".:", true); int t, m, j, s = 0, min = 0; t = Integer. parseint ( to. nexttoken ()); if (!to. nexttoken (). equals(".")) m = Integer. parseint ( to. nexttoken ()); if (!to. nexttoken (). equals(".")) j = Integer. parseint ( to. nexttoken ()); if (to. hasmoretokens ()) { if (!to. nexttoken (). equals(" ")) s = Integer. parseint ( to. nexttoken ()); if (!to. nexttoken (). equals(":")) min = Integer. parseint ( to. nexttoken ()); catch ( Exception ex) { boolean schaltjahr = (( j%4 == 0 && j%100!= 0) j%400 == 0); int[] a; if ( schaltjahr ) a = monattages ; a = monattage ; // Ueberpruefe Jahr if (j < 1970) // Ueberpruefe Monat if (m < 0 m > 12) // Ueberpruefe Tag if (t < 0 t > a[m - 1]) // Ueberpruefe Stunde if (s < 0 s > 23) // Ueberpruefe Minute if ( min < 0 min > 59) // Berechne Tag im laufenden Jahr. int tagimjahr = t; for (int i = 0; i < m - 1; i++) tagimjahr += a[i]; // Berechne Anzahl der Schaltjahre von 1970 bis einschl. j-1 int anzahls = ((j - 1) / 4) - ((j - 1) / 100) + ((j - 1) / 400) - 477; // Berechne Anzahl der Tage der Jahr 1970 bis einschl. j-1 int tag = (( j ) * 365) + anzahls; int minute = tag * 24 * 60 + s * 60 + min; return minute;

3 Lösung 10/ Seite 3 import java. util.*; public class Termin{ private int dauer, start; private String beschreibung, ort; public Termin(int start, int dauer, String beschreibung, String ort) throws NegativeDauerException { if ( dauer < 0) throw new NegativeDauerException ( dauer ); this. start = start; this. dauer = dauer; this. beschreibung = beschreibung ; this. ort = ort; public Termin( String start, int dauer, String beschreibung, String ort) throws DatumsformatException, NegativeDauerException { this( Converter. convertzeit ( start), dauer, beschreibung, ort ); public Termin( String start, String ende, String beschreibung, String ort) throws DatumsformatException, NegativeDauerException { this( Converter. convertzeit ( start), Converter. convertzeit ( ende) - Converter. convertzeit ( start), beschreibung, ort ); public int getdauer () { return dauer; public int getstart () { return start; public int getende () { return start + dauer; public String getort (){ return ort; public String tostring (){ return " Termin: start = " + start + ", dauer = " + dauer + ", ort = " + ort + ", beschreibung = " + beschreibung ; public boolean ueberschneidung ( Termin t) { return getstart () < t. getende () && getende () > t. getstart (); import java. util.*; public class Kalender { private List <Termin > termine = new LinkedList <Termin >(); public void trageterminein ( Termin termin) throws TerminUeberschneidungException { for ( Termin t : termine) if ( termin. ueberschneidung (t)) throw new TerminUeberschneidungException ( termin,t); termine. add( termin );

4 Lösung 10/ Seite 4 public Termin nachfolger ( Termin t) throws KeinNachfolgerException { Termin retval = null; int d = Integer. MAX_VALUE ; for ( Termin _t : termine) { int _d = _t. getstart () - t. getende (); if (_d >= 0 && _d <= d) { d = _d; retval = _t; if ( retval == null) throw new KeinNachfolgerException (t); return retval; public List <Termin > terminetag ( String datum) throws DatumsformatException { List <Termin > retval = new LinkedList <Termin >(); int min = Converter. convertzeit ( datum ); System. out. println( min + ""); for ( Termin t : termine) if ( (t. getstart () / 1440 == min / 1440) (t. getende () / 1440 == min / 1440 ) ) retval. add(t); return retval; public Termin termintag ( String datum,int i) throws DatumsformatException { return terminetag ( datum ). get(i); public String tostring () { StringBuffer retval = new StringBuffer (" Kalender = \n"); for ( Termin t : termine) retval. append(t + "\n"); return retval + ""; public class TerminUeberschneidungException extends TerminException { private Termin neuertermin, vorhandenertermin ; public TerminUeberschneidungException ( Termin neu, Termin vorhanden ) { neuertermin = neu; vorhandenertermin = vorhanden ; public Termin getneuertermin () { return neuertermin ; public Termin getvorhandenertermin () { return vorhandenertermin ; public class TerminException extends Exception { public TerminException () { public class NegativeDauerException extends TerminException { private int dauer; public NegativeDauerException (int d) { dauer = d; public String getmessage () { return dauer + ""; public class DatumsformatException extends Exception { private String datum;

5 Lösung 10/ Seite 5 public DatumsformatException ( String d){ datum = d; import java. util.*; public class Test extends MiniJava { public static void main( String [] args) { Kalender kalender = new Kalender (); while (true) { write("0 = ende; 1 = eintragen ; 2 = termine eines tages; 3 = i- ter termin"); int auswahl = read (); if ( auswahl == 0) return; if ( auswahl == 1) { while (true) { String s = readstring (); String e = readstring (); String b = readstring (); String o = readstring (); Termin t = new Termin(s,e,b,o); kalender. trageterminein (t); break; catch ( DatumsformatException ex) { write(" Falsches Datumsformat!"); catch ( NegativeDauerException ex) { write(" Negative Dauer!"); catch ( TerminUeberschneidungException ex) { write(" Ueberschneidung!"); if ( auswahl == 2) { while (true) { String tag = readstring (); List <Termin > l = kalender. terminetag ( tag ); for ( Termin t : l) write(t + ""); break; catch ( DatumsformatException ex) { write(" Falsches Datumsformat!"); if ( auswahl == 3) { while (true) { String tag = readstring (); int i = read (); Termin t = kalender. termintag (tag, i - 1); write(t + ""); break; catch ( DatumsformatException ex) { write(" Falsches Datumsformat!"); catch ( IndexOutOfBoundsException ex) { write(" kein " + i + "-ter Termin"); Aufgabe 48 ContentCrawler (Lösungsvorschlag) import java. io. FileNotFoundException ; import java. io. FilterReader ; import java. io. IOException ; import java. io. InputStreamReader ; import java. io. Reader; import java. net. URL; import java. util. ArrayList ; import java. util. Collections ;

6 Lösung 10/ Seite 6 import java. util. Comparator ; import java. util. HashSet; import java. util. Hashtable ; import java. util. List; import java. util. Map; import java. util. Set; public class ContentCrawler { public static void main( String [] args) { List <String > urls = new ArrayList <String >(); int maxvisits = 100; if ( args. length == 0) { urls.add("http :// { urls. add( args [0]); if ( args. length > 1) { maxvisits = Integer. parseint ( args [1]); catch ( NumberFormatException e) { System. out. println(" The second parameter has to be an int value, defining how many pages are visited."); return; Map <String, Integer > topics = new Hashtable <String, Integer >(); int visits = 0; for (int i = 0; i < urls. size () && visits < maxvisits ; i++) { String url = urls. get(i); System. out. println(" Processing page " + url ); DictionaryFilterReader s = new DictionaryFilterReader ( new HtmlFilterReader ( new UrlExtractorFilter ( new InputStreamReader ( new URL(url ). openstream (),"UTF -8"),urls )), topics ); while ((s.read ())!= -1); s.close (); visits ++; catch ( FileNotFoundException e) { System. out. println(" Page " + url + " can t be accessed"); catch ( IOException e) { System. out. println(" Error: " + e. tostring ()); System. out. println(" Processed " + visits + " pages."); Set <Map. Entry <String, Integer >> set = topics. entryset (); List <Map. Entry <String, Integer >> entries = new ArrayList <Map. Entry <String, Integer >>( set ); Collections. sort( entries, new Comparator <Map. Entry <String, Integer >>() { public int compare( Map. Entry <String, Integer > e1, Map. Entry <String, Integer > e2) { ); return ( e1. getvalue (). compareto ( e2. getvalue ()) * ( -1)); // sort in descending order int maxoutput = 10; int output = 0; for ( Map. Entry <String, Integer > entry : entries) { output ++; System. out. println( entry. getkey () + "\t\t" + entry. getvalue ()); if ( output >= maxoutput ) break;

7 Lösung 10/ Seite 7 class DictionaryFilterReader extends FilterReader { private Map <String, Integer > topics; private Set <String > words = new HashSet <String >(); private String currentword = null; protected DictionaryFilterReader ( Reader reader, Map <String, Integer > topics) { super( reader ); this. topics = topics; public Map <String, Integer > gettopics () { return topics; public int read () throws IOException { int i = super. read (); char c = (char) i; if ( currentword == null) { if ( isalphabeticalcharacter (c)) currentword = String. valueof(c); { if (! isalphabeticalcharacter (c)) { if ( currentword. length () > 5 && currentword. substring (0,1). equals( currentword. substring (0,1). touppercase ())) { if (! words. contains ( currentword )) { words. add( currentword ); if (! topics. containskey ( currentword )) topics. put( currentword,1); topics. put( currentword, topics. get( currentword )+1); currentword = null; currentword += String. valueof(c); return i; public boolean isalphabeticalcharacter (char c) { // decide by ascii code if (c >=65 && c <= 90) return true; // A-Z if (c >= 97 && c<= 122) return true; // a-z if (c == ä c== Ä c == return true; return false; ü c == Ü c == ö c == Ö c == ß ) class UrlExtractorFilter extends FilterReader { private List <String > urls = new ArrayList <String >(); private String url = null; private String lastchars = ""; protected UrlExtractorFilter ( Reader reader, List <String > urls) { super( reader ); this. urls = urls;

8 Lösung 10/ Seite 8 public int read () throws IOException { int i = super. read (); // save URL values if (url!= null) { if (i == \" ) { url = url. tolowercase (); if (! urls. contains ( url) && url. startswith (" http ://") && url. endswith (" html")) urls.add(url ); url = null; { url += String. valueof ((char) i); // check if we have an url value lastchars += String. valueof ((char) i); if ( lastchars. tolowercase (). endswith ("href =\"")) { url = ""; if ( lastchars. length () > 6) lastchars = lastchars. substring ( lastchars. length () -6); return i; class HtmlFilterReader extends FilterReader { private int levelcount = 0; protected HtmlFilterReader ( Reader reader) { super( reader ); public int read () throws IOException { int i = super. read (); if (i == -1) return i; if (i == < ) { levelcount ++; return read (); if (i == > ) { levelcount --; return read (); if ( levelcount == 0) return i; return read ();