Dictionaries

Chapter 17

Slides by Steve ArmstrongLeTourneau University

Longview, TX2007,Prentice Hall

Carrano, Data Structures and Abstractions with Java, Second Edition, (c) 2007 Pearson Education, Inc. All rights reserved. 0-13-237045-X

Chapter Contents

• Specifications for the ADT Dictionary A Java Interface Iterators

• Using the ADT Dictionary A Directory of Telephone Numbers The Frequency of Words A Concordance of Words

• Java Class Library: the Interface Map

Carrano, Data Structures and Abstractions with Java, Second Edition, (c) 2007 Pearson Education, Inc. All rights reserved. 0-13-237045-X

Specifications for the ADT Dictionary 1

• Contains entries that each have two parts A key word or search key A value associated with the key

Fig. 17-1 An English dictionary.

Carrano, Data Structures and Abstractions with Java, Second Edition, (c) 2007 Pearson Education, Inc. All rights reserved. 0-13-237045-X

Specifications for the ADT Dictionary

Fig. 17-2 An instance of an ADT dictionary has pairs of search keys and corresponding values

Carrano, Data Structures and Abstractions with Java, Second Edition, (c) 2007 Pearson Education, Inc. All rights reserved. 0-13-237045-X

Specifications for the ADT Dictionary 2

• Data Pairs of objects (key, value) Number of pairs in the collection

• Operations• add

• remove

• retrieve

• contains

• traverse keys

• traverse values

• isFull

• get number of entries

• remove all entries

Carrano, Data Structures and Abstractions with Java, Second Edition, (c) 2007 Pearson Education, Inc. All rights reserved. 0-13-237045-X

Specifications for the ADT Dictionary 3

• Additional refinement possibilities Distinct search keys vs. Duplicate search keys Secondary search keys

• View Java source code for interface

Carrano, Data Structures and Abstractions with Java, Second Edition, (c) 2007 Pearson Education, Inc. All rights reserved. 0-13-237045-X

Iterators 6• Note that getKeyIterator and getValueIterator

return iterators Create iterators for a dictionary dataBase with

• Possible to traverse All search keys in dictionary without traversing values All values without traversing search keys All search keys and values in parallel

Carrano, Data Structures and Abstractions with Java, Second Edition, (c) 2007 Pearson Education, Inc. All rights reserved. 0-13-237045-X

Iterators

Fig. 17-3 Two iterators that traverse a dictionary's keys and values in parallel.

Carrano, Data Structures and Abstractions with Java, Second Edition, (c) 2007 Pearson Education, Inc. All rights reserved. 0-13-237045-X

Using the ADT Dictionary 7

• A directory of telephone numbers

Fig 17-4 A class diagram for a telephone directory.

Carrano, Data Structures and Abstractions with Java, Second Edition, (c) 2007 Pearson Education, Inc. All rights reserved. 0-13-237045-X

A Directory of Telephone Numbers

• Consider a client of the class TelephoneDirectory as specified in Fig. 17-4 View source code Note output

• View source code of class TelephoneDirectory

Carrano, Data Structures and Abstractions with Java, Second Edition, (c) 2007 Pearson Education, Inc. All rights reserved. 0-13-237045-X

The Frequency of Words 12

• We seek an ADT that will enable us to count each occurrence of a word as it is read from a text file

• View client program which uses FrequenceyCounter Note output

• View class FrequencyCounter used by the client

Carrano, Data Structures and Abstractions with Java, Second Edition, (c) 2007 Pearson Education, Inc. All rights reserved. 0-13-237045-X

A Concordance of Words 18• Provide an index for finding a word in a file

Index would give the page number A concordance would give the line number of a

word (in a smaller file of words)

• A word may appear multiple times in the file Appears once in index/concordance The associated data is a list of page/line numbers

• View class Concordance

Carrano, Data Structures and Abstractions with Java, Second Edition, (c) 2007 Pearson Education, Inc. All rights reserved. 0-13-237045-X

Java Class Library: The Interface Map 22

• Package java.util contains interfaceMap <K, V> Similar to our ADT dictionary

• View list of method headers Note similarity to methods developed in this

chapter Differences from our methods are highlighted