Administrivia. CSSS Movie Night: Zombieland & Iron Man Date: Thurs., Mar 11 Time: 6 10 pm Location: DMP 310 Free pop & popcorn for every attendee!

Transcription

1 Department of Computer Science Undergraduate Events Events this week Drop-In Resume and Cover Letter Editing (20 min. appointments) Date: Thurs., March 11 Time: 11:30 am 2:30 pm Location: Rm 255, ICICS/CS Townhall Meeting for Combined Majors /Honours, Cogs, BA, B.Comm in CS Date: Thurs., March 11 Time: 12:30 2 pm Location: DMP 310 Lumch will be provided! CS Distinguished Lecture Series Featuring David Parkes Title: Incentive Mechanism Engineering in the Internet Age Date: Thurs., Mar 11 Time: 3:30 4:50 pm Location: DMP 110 CSSS Movie Night: Zombieland & Iron Man Date: Thurs., Mar 11 Time: 6 10 pm Location: DMP 310 Free pop & popcorn for every attendee! Events next week Interview Skills Practice Session Mon., March 15, 12 2 pm, Rm 202, ICICS/CS Transport Canada Info Session Tues., March 16, 4 6 pm, HENN 201 Financial Literacy 101 Wed., March 17, 12 1 pm, Angus 426 Townhall Meeting for CS Major/Honours Students Thurs., March 18, 12:30 2 pm, DMP 310 CS Distinguished Lecture Series Featuring Jeff Hawkins Thurs., March 18, 3:30 4:50 pm, DMP Administrivia Assignment #3 is out Due Thursday March 18, 10:00pm Midterm exam Wednesday March 10, 6:00pm Math 100 (BCS and 202 sections) You will be given helps (UML, APIs) No labs this week until Friday Lab weeks start on Fridays from now on Final exam schedule is now posted CPSC Apr 23, 7:00pm No location yet announced 2

2 Maps, Stacks, Queues and Generic Algorithms You will be expected to: program to the generic Map and SortedMap interfaces by reading and using the API compare and contrast HashMap and TreeMap classes (benefits of using each, basic run time analysis) program to the generic Queue interface program to the API of the generic Stack class program to the API of the generic Deque class identify (in words or through code) appropriate types for collections of data needed in a given software system write code (solve problems) that uses the generic algorithms provided in the Collections class Reading: 2 nd Ed: 20.4, 21.2, rd Ed: 15.4, 16.2, th Ed: 15.4, 16.2 Additional references: Online Java Tutorial at /books/tutorial/collectio ns/ The Map Interface A map structure is also known as a table or dictionary or association list. A map is a collection of pairs (key, value). The keys are unique within the map The map associates exactly one value with each key Examples: map of student ids to student records map of words to frequency of occurrence in a document

3 The Map Interface The Map interface is not related to the other interfaces in the Java Collections Framework: Map does not extend Iterable (so you can't iterate over a map or use the for-each loop) Map does not extend Collection a Collection operates on items a Map manipulates (key, value) pairs The Map Interface (cont ) public interface Map<K,V> { // Basic Operations int size(); boolean isempty(); boolean containskey(object key); boolean containsvalue(object value); V get(object key); V remove(object key); V put(k key, V value); // Bulk Operations void clear(); void putall(map<? extends K,? extends V> m);

4 The Map Interface (cont ) // Collection Views Set<K> keyset(); Collection<V> values(); Set<Map.Entry<K,V>> entryset(); } // Interface for entryset elements; defined inside Map interface Entry<K,V> { K getkey(); V getvalue(); V setvalue(v value); } Map Methods Basic methods: put adds a (key, value) entry; returns previous value for that key or null containskey, containsvalue check if a key or value is in the map get returns the value of a given key; returns null if key is not in the map problems if map allows null values; must use containskey remove removes the entry for that key; returns the value removed or null if the map doesn't contain the given key

5 Map Methods Collection Views: restructure the map (or parts of it) as a Collection so we can use iterators: keyset returns a Set containing all keys in the map values returns a Collection with all map values (may have duplicates) entryset returns a Set of entries; each entry represents a (key, value) pair and it is defined by the interface Entry defined inside Map Map Implementations The class HashMap provides an implementation of the Map interface. The underlying implementation is similar to a HashSet (it uses a hash table) When a ( key, value ) pair is added to a HashMap, the hash code is generated using only the key (not the value) Assuming a good hashcode() method for the Key, the put, get and remove methods run in O(1) time.

6 Map Examples A function that returns a map of words to the number of times each word occurs in a text document (doc): public static Map<String, Integer> frequencies(collection<string> doc) { Map<String,Integer> map = new HashMap<String,Integer>(); for (String word : doc) { if ( map.containskey(word) ) map.put(word, map.get(word) + 1); else map.put(word, 1); } Map Examples A generic method that prints out all the key-value pairs of a Map: public static <K,V> void printmap( Map<K,V> themap ) { for(map.entry<k,v> e : themap.entryset()) { System.out.println(e.getKey() + ": " + e.getvalue()); } Exercise: Write the same function using an iterator instead of a for-each loop.

7 Sorted Map The SortedMap interface extends the Map interface. A SortedMap maintains the entries in the map sorted by their key (not their value) The class TreeMap implements the SortedMap interface TreeMap uses a similar underlying implementation to TreeSet. The get, put and remove operations run in O( log N ) time. Sorted Map The TreeMap<K,V> has the following constructors (note the similarity with TreeSet): public TreeMap() // orders the entries using the natural // ordering for the Key public TreeMap( Comparator<? super K > c ) // orders the entries using the given // comparator for the Key

8 SortedMap Interface public interface SortedMap<K, V> extends Map<K, V> { // Range-view SortedMap<K, V> submap(k fromkey, K almosttokey); SortedMap<K, V> headmap(k almosttokey); SortedMap<K, V> tailmap(k fromkey); // Endpoints K firstkey(); K lastkey(); } // Comparator access Comparator<? super K> comparator(); Graphical User Interfaces I Reading 2 nd Ed: Chapter 14 3 rd and 4 th Ed: Chapter 18 References:

9 Learning Objectives describe basic principles of good user interface design given a typical set of Java GUI components, be able to explain how it was created use layout managers to produce a well designed GUI write code to produce a well designed GUI that includes frames, panels, menus and buttons Types of User Interfaces Command-line interfaces User specifies program behaviour through command-line arguments, or command typed at a prompt Pro: it is fast, especially for massive operations (commands can be read from scripts to control the programs) Con: difficult to use; requires memorizing commands Text-based menus User is presented with menus and prompts throughout Pro: easy to use, easy to program Con: it is slow to use

10 Types of User Interfaces Graphical user interfaces Use multiple input modes (keyboard + mouse) Pro: more intuitive and very easy to use Con: more difficult to program GUI Design Guidelines A GUI should be: as simple as possible (should make things easier not harder) intuitive (explicit dialogs, etc.) consistent (follow conventions) aesthetically pleasing not distracting provide feedback to the user have undo/exit/cancel options when appropriate and possible accommodate multiple skill levels (allow keyboard and mouse input)

11 Swing Components Swing is a collection of classes that allows us to incorporate a graphical user interface into a Java program A Swing GUI contains: Components (JComponent) Parts of the user interface that we interact with Examples: buttons, labels, text fields, scroll panes, menus Panels (JPanel) Borderless windows, used to group components together Can contain components or other panels Each JPanel has an associated layout that determines how the components inside the panel are placed Windows: Frames (JFrame), Dialogs (JDialog, JOptionPane) Each JFrame has a title a menu bar a content pane (an instance of JPanel) into which other elements can be added GUI Example Here's a sample screen snapshot JFrame JMenuBar JScrollPane JToolBar JList JPanel JButton

12 Containment Hierarchy GUI components can be nested The GUI's containment hierarchy Represents the structure of the user interface for a specific application Shows which components contain which other components. Components that can contain other components are usually called containers. The containment hierarchy for the example is on next page. Containment Hierarchy Example frame menu bar tool bar content pane scroll pane panel course list delete button recommend button

13 Layout Managers A layout manager is responsible for laying out components (buttons, labels, etc.) inside a container (like a panel) Border Layout (default for a JFrame's content pane): has north, south, east, west, center regions Layout Managers Here is how we could create the picture on the previous page: public class Border extends JFrame { public Border(String title) { super(title); Container cp = getcontentpane(); cp.setlayout(new BorderLayout()); cp.add(new JButton("Center"), BorderLayout.CENTER); cp.add(new JButton("North"), BorderLayout.NORTH); cp.add(new JButton("South"), BorderLayout.SOUTH); cp.add(new JButton("East"), BorderLayout.EAST); cp.add(new JButton("West"), BorderLayout.WEST); pack(); setvisible(true); } }

14 Layout Managers Flow Layout: places components from left to right, with their centres aligned can specify row alignment (LEFT, CENTER, RIGHT) default for JPanel Layout Managers Box Layout: places components in a horizontal box from left to right, or in a vertical box from top to bottom.

15 Layout Managers Grid Layout: places components in a grid number of rows and columns in grid is specified by client all grid boxes are the same size