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UNDERSTANDING RECURSIVE CLASSES CMSC 150: Lecture 22.

Published byAron Casey Modified over 9 years ago

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Presentation on theme: "UNDERSTANDING RECURSIVE CLASSES CMSC 150: Lecture 22."— Presentation transcript:

1 UNDERSTANDING RECURSIVE CLASSES CMSC 150: Lecture 22

2 StringList: A Recursive Class public class StringList { // instance variables private boolean isEmpty; private String thisString; private StringList restOfStringList; // constructors public StringList() { … } public StringList(String newString, StringList aList) { … } public String toString() { … } public String getLineStartingWith(String prefix) { … } }

3 StringList: A Recursive Class public class StringList { // instance variables private boolean isEmpty; private String thisString; private StringList restOfStringList; // constructors public StringList() { … } public StringList(String newString, StringList aList) { … } public String toString() { … } public String getLineStartingWith(String prefix) { … } } Data

4 StringList: A Recursive Class public class StringList { // instance variables private boolean isEmpty; private String thisString; private StringList restOfStringList; // constructors public StringList() { … } public StringList(String newString, StringList aList) { … } public String toString() { … } public String getLineStartingWith(String prefix) { … } } Methods

5 StringList: A Recursive Class public class StringList { // instance variables private boolean isEmpty; private String thisString; private StringList restOfStringList; // constructors public StringList() { … } public StringList(String newString, StringList aList) { … } public String toString() { … } public String getLineStartingWith(String prefix) { … } }

6 StringList: In Action  StringList aList = new StringList(); aList true "" toString() getLine() public class StringList { // instance variables private boolean isEmpty; private String thisString; private StringList restOfStringList; // constructors public StringList() { … } public StringList(String newString, StringList aList) { … } public String toString() { … } public String getLineStartingWith(String prefix) { … } } addr: 32 32 0

7 StringList: In Action  StringList aList = new StringList(); aList true "" toString() getLine() Actually a reference to a String object, but for brevity… addr: 32 32 0 public class StringList { // instance variables private boolean isEmpty; private String thisString; private StringList restOfStringList; // constructors public StringList() { … } public StringList(String newString, StringList aList) { … } public String toString() { … } public String getLineStartingWith(String prefix) { … } }

8 StringList: In Action  StringList aList = new StringList();  aList = new StringList("mandolin", aList); aList true "" toString() getLine() addr: 32 32 0

9 StringList: In Action  StringList aList = new StringList();  aList = new StringList("mandolin", aList); aList true "" toString() getLine() toString() getLine() false addr: 32 32 addr: 48 0

10 StringList: In Action  StringList aList = new StringList();  aList = new StringList("mandolin", aList); aList true "" toString() getLine() toString() getLine() "mandolin" false addr: 32 32 0 addr: 48

11 StringList: In Action  StringList aList = new StringList();  aList = new StringList("mandolin", aList); aList true "" toString() getLine() toString() getLine() "mandolin" false addr: 32 32 0 addr: 48

12 StringList: In Action  StringList aList = new StringList();  aList = new StringList("mandolin", aList); aList true "" toString() getLine() toString() getLine() "mandolin" false addr: 32 32 0 addr: 48 32

13 StringList: In Action  StringList aList = new StringList();  aList = new StringList("mandolin", aList); aList true "" toString() getLine() toString() getLine() "mandolin" false addr: 32 32 0 addr: 48 32

14 StringList: In Action  StringList aList = new StringList();  aList = new StringList("mandolin", aList); aList true "" toString() getLine() toString() getLine() "mandolin" false addr: 32 32 0 addr: 48 32

15 StringList: In Action  StringList aList = new StringList();  aList = new StringList("mandolin", aList); aList true "" toString() getLine() toString() getLine() "mandolin" false addr: 32 32 0 addr: 48 32

16 StringList: In Action  StringList aList = new StringList();  aList = new StringList("mandolin", aList); aList true "" toString() getLine() toString() getLine() "mandolin" false addr: 32 48 0 addr: 48 32

17 StringList: In Action  StringList aList = new StringList();  aList = new StringList("mandolin", aList); aList true "" toString() getLine() toString() getLine() "mandolin" false addr: 32 48 0 addr: 48 32

18 StringList: In Action  StringList aList = new StringList();  aList = new StringList("mandolin", aList);  aList = new StringList("Lilly", aList); aList true "" toString() getLine() toString() getLine() "mandolin" false addr: 32 48 0 addr: 48 32

19 StringList: In Action  StringList aList = new StringList();  aList = new StringList("mandolin", aList);  aList = new StringList("Lilly", aList); aList true "" toString() getLine() toString() getLine() "mandolin" false addr: 32 48 0 addr: 48 32 toString() getLine() false addr: 77 "Lilly" 48

20 StringList: In Action  StringList aList = new StringList();  aList = new StringList("mandolin", aList);  aList = new StringList("Lilly", aList); aList true "" toString() getLine() toString() getLine() "mandolin" false addr: 32 48 0 addr: 48 32 toString() getLine() false addr: 77 "Lilly" 48

21 StringList: In Action  StringList aList = new StringList();  aList = new StringList("mandolin", aList);  aList = new StringList("Lilly", aList); aList true "" toString() getLine() toString() getLine() "mandolin" false addr: 32 77 0 addr: 48 32 toString() getLine() false addr: 77 "Lilly" 48

22 HistoryList: A Recursive Class public class HistoryList { // instance variables private boolean isEmpty; private String firstWebSite; private HistoryList restOfWebSites; // constructors public HistoryList() { … } public HistoryList(String newSite, HistoryList aList) { … } public boolean contains(String site) { … } public String toString() { … } public HistoryList getMatches(String prefix) { … } public boolean isEmpty() { … } }

23 HistoryList: In Action  HistoryList aList = new HistoryList();  aList = new HistoryList("cnn.com", aList);  aList = new HistoryList("mlb.com", aList); aList true "" contains() toString() getMatches() isEmpty() "cnn.com" false addr: 42 87 0 addr: 58 42 false addr: 87 "mlb.com" 58 contains() toString() getMatches() isEmpty() contains() toString() getMatches() isEmpty()

24 HistoryList: contains() method public boolean contains(String site) { if (empty) { return false; } else if (firstWebSite.equals(site)) { return true; } return restOfWebSites.contains(site); }

25 HistoryList: contains()  boolean inList = aList.contains("cnn.com"); aList true "" contains() toString() getMatches() isEmpty() "cnn.com" false addr: 42 87 0 addr: 58 42 false addr: 87 "mlb.com" 58 contains() toString() getMatches() isEmpty() contains() toString() getMatches() isEmpty()

26 HistoryList: contains()  boolean inList = aList.contains("cnn.com"); aList true "" contains() toString() getMatches() isEmpty() "cnn.com" false addr: 42 87 0 addr: 58 42 false addr: 87 "mlb.com" 58 contains() toString() getMatches() isEmpty() contains() toString() getMatches() isEmpty()

27 HistoryList: contains()  boolean inList = aList.contains("cnn.com"); aList true "" contains() toString() getMatches() isEmpty() "cnn.com" false addr: 42 87 0 addr: 58 42 false addr: 87 "mlb.com" 58 contains() toString() getMatches() isEmpty() contains() toString() getMatches() isEmpty()

28 HistoryList: contains()  boolean inList = aList.contains("cnn.com"); aList true "" contains() toString() getMatches() isEmpty() "cnn.com" false addr: 42 87 0 addr: 58 42 false addr: 87 "mlb.com" 58 contains() toString() getMatches() isEmpty() contains() toString() getMatches() isEmpty()

29 HistoryList: contains()  boolean inList = aList.contains("cnn.com"); aList true "" contains() toString() getMatches() isEmpty() "cnn.com" false addr: 42 87 0 addr: 58 42 false addr: 87 "mlb.com" 58 contains() toString() getMatches() isEmpty() contains() toString() getMatches() isEmpty()

30 true "" contains() toString() getMatches() isEmpty() "cnn.com" false addr: 42 87 0 addr: 58 42 false addr: 87 "mlb.com" 58 contains() toString() getMatches() isEmpty() if (empty){ return false; } else if (firstWebSite.equals(site)) { return true; } return restOfWebSites.contains(site); contains() toString() getMatches() isEmpty() aList

31 true "" contains() toString() getMatches() isEmpty() "cnn.com" false addr: 42 87 0 addr: 58 42 false addr: 87 "mlb.com" 58 contains() toString() getMatches() isEmpty() contains() toString() getMatches() isEmpty() aList if (empty){ return false; } else if (firstWebSite.equals(site)) { return true; } return restOfWebSites.contains(site);

32 true "" contains() toString() getMatches() isEmpty() "cnn.com" false addr: 42 87 0 addr: 58 42 false addr: 87 "mlb.com" 58 contains() toString() getMatches() isEmpty() contains() toString() getMatches() isEmpty() aList if (empty){ return false; } else if (firstWebSite.equals(site)) { return true; } return restOfWebSites.contains(site);

33 true "" contains() toString() getMatches() isEmpty() "cnn.com" false addr: 42 87 0 addr: 58 42 false addr: 87 "mlb.com" 58 contains() toString() getMatches() isEmpty() contains() toString() getMatches() isEmpty() aList if (empty){ return false; } else if (firstWebSite.equals(site)) { return true; } return restOfWebSites.contains(site);

34 true "" contains() toString() getMatches() isEmpty() "cnn.com" false addr: 42 87 0 addr: 58 42 false addr: 87 "mlb.com" 58 contains() toString() getMatches() isEmpty() contains() toString() getMatches() isEmpty() aList if (empty){ return false; } else if (firstWebSite.equals(site)) { return true; } return restOfWebSites.contains(site);

35 true "" contains() toString() getMatches() isEmpty() "cnn.com" false addr: 42 87 0 addr: 58 42 false addr: 87 "mlb.com" 58 contains() toString() getMatches() isEmpty() contains() toString() getMatches() isEmpty() aList if (empty){ return false; } else if (firstWebSite.equals(site)) { return true; } return restOfWebSites.contains(site);

36 true "" contains() toString() getMatches() isEmpty() "cnn.com" false addr: 42 87 0 addr: 58 42 false addr: 87 "mlb.com" 58 contains() toString() getMatches() isEmpty() contains() toString() getMatches() isEmpty() aList if (empty){ return false; } else if (firstWebSite.equals(site)) { return true; } return restOfWebSites.contains(site);

37 true "" contains() toString() getMatches() isEmpty() "cnn.com" false addr: 42 87 0 addr: 58 42 false addr: 87 "mlb.com" 58 contains() toString() getMatches() isEmpty() contains() toString() getMatches() isEmpty() aList if (empty){ return false; } else if (firstWebSite.equals(site)) { return true; } return restOfWebSites.contains(site);

38 true "" contains() toString() getMatches() isEmpty() "cnn.com" false addr: 42 87 0 addr: 58 42 false addr: 87 "mlb.com" 58 contains() toString() getMatches() isEmpty() contains() toString() getMatches() isEmpty() aList if (empty){ return false; } else if (firstWebSite.equals(site)) { return true; } return restOfWebSites.contains(site); true

39 "" contains() toString() getMatches() isEmpty() "cnn.com" false addr: 42 87 0 addr: 58 42 false addr: 87 "mlb.com" 58 contains() toString() getMatches() isEmpty() contains() toString() getMatches() isEmpty() aList if (empty){ return false; } else if (firstWebSite.equals(site)) { return true; } return restOfWebSites.contains(site); true

40 "" contains() toString() getMatches() isEmpty() "cnn.com" false addr: 42 87 0 addr: 58 42 false addr: 87 "mlb.com" 58 contains() toString() getMatches() isEmpty() contains() toString() getMatches() isEmpty() aList if (empty){ return false; } else if (firstWebSite.equals(site)) { return true; } return restOfWebSites.contains(site); true

41 HistoryList: contains()  boolean inList = aList.contains("cnn.com"); true "" contains() toString() getMatches() isEmpty() "cnn.com" false addr: 42 87 0 addr: 58 42 false addr: 87 "mlb.com" 58 contains() toString() getMatches() isEmpty() contains() toString() getMatches() isEmpty() aList true

42 HistoryList: contains()  boolean inList = aList.contains("cnn.com"); true "" contains() toString() getMatches() isEmpty() "cnn.com" false addr: 42 87 0 addr: 58 42 false addr: 87 "mlb.com" 58 contains() toString() getMatches() isEmpty() contains() toString() getMatches() isEmpty() aList true

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