CS 240 Week 4

1. CS 240Week 4

2. Evil Hangman • java Hangman wordLengthguesses • Run Demo • Building a pattern for the letters guessed so far • Data Structures • Set of T: Set<T> • Set of words of proper length – Set<String> • Set of words that match a pattern – Set<String> • Map from Key to Value: Map< Key_Type, Value_Type> • Map from pattern to set of words matching that pattern • Map<String, Set<String>> • List of T: List<T> • List of sets of Maximum Size: List of prospective pattern/set of word pairs • The set of words associated with the prospective pattern must match the associated pattern •  p ∈ list of sets of Maximum Size (¬ q ∈ all pattern/set of word pairs ^ |q.set of word| > |p.set of word|) • Java syntax: Map.Entry<String, Set<String>> • Each entry is a key, value pair in a Map • List of sets of Maximum Number of Blanks: List of pattern,/set of word pairs such that •  p ∈ list of sets of Maximum Number of Blanks (p ∈ list of sets of Maximum Size ^ ¬ q ∈ list of sets of Maximum Size (numberOfBlanksIn(q.pattern) > numberOfBlanksIn(p.patterhn))) • Java syntax: Map.Entry<String, Set<String>> • Each entry is a key, value pair in a Map

3. Basic Algorithm(Terribly Inefficient) • Create a list of words • Start with blank pattern of appropriate size • e.g. “------” • Repeat the following until the word has been guessed or the player has exceeded the number of guesses • For every guess create all possible patterns from the current pattern where the guessed letter has been substituted for zero or more of the blanks • For each of these new patterns create patttern/set of matching word pairs • Create the set of all pattern/set of matching word pairs that have the maximum number of matching words for the corresponding pattern • From that set create a subset of pairs such that the pattern has the most number of blanks • Select a pair, p, from the resulting set • If |p.set of matching word pairs| = 1 the player has guessed the word else set the current pattern to p.pattern and have the player guess again

4. Reading from Standard.in • new Scanner(System.in)

5. Inner Classes • Standard Inner Classes – usually just called inner classes • Local Inner Classes – classes declared within a method • Anonymous Inner Classes – classes declared within a method but it has no name. • At the same time you define the class, you create a single instance of the class. • Usually, when defining the class you override at least one method in the class

6. Inner Classes • Declare a class inside another class • Example: declare the class Iterator inside the class Stuff. Make it extend Iterator. • Now we can declare: • Stuff.Iteratoriter = stuff.iterator(); • Inner classes can be public, private, or protected • Example • Main.java • Node.java • Graph.java

7. Local Inner Classes • Classes declared in a method • No visibility designator • A weaker form of closure • Example • Main.java

8. Anonymous Inner Classes • Inner classes declared on the fly in a metod • No visibility designator • A weaker form of closure • Used extensively in GUIs • Syntax new T(…) { public void foo() { //overridden method of } } • Version of command pattern • How do you pass method as parameter • Example • Main.java • Integral.java

9. Java Collections • From the library • See the java api • Simple Generics • Parameters • The parameters may be generic • C<X, Y, Z> • Parameters cannot be of atomic type • Abstract Class or Interface vs. Concrete • List: ArrayList, LinkedList, Stack, Vector • Set: HashSet, TreeSet • Map: HashMap, HashTable • Iterators

10. Iterators • Iterator<Integer> iter = someSet.iterator(); • hasNext() • next() • Interface Iterable<T> • Example of use 1: Iterator<String> iter = studentList.iterator() while(iter.hasNext()){ String str = iter.next(); … } • Example of use 2: for-each loop for(String str : studentList) { … } • studentList must implement Iterable • It does if it is declared as ArrayList<String> studentList;

11. Lists • List<T> • Common methods • add(T t) hashCode() • add(int index, T t) isEmpty() • clear() iterator() • contains(T t) indexOf(Object o) • equals(Object o) remove(int index) • get(int index) remove(Object o) • set(int index, T t) size() • subList(int from, int to) • List Example • To run this you also need Name.java • Notice the use of interfaces for Comparable objects

12. Sets • Set<T> • Common methods • add(T t) iterator() • clear() remove(Object o) • contains(T t) size() • equals(Object o) • hasCode() • isEmpty() • Sets Example • To run this you also need Name.java

13. Map • Map<KeyType, ValueType> • Map.Entry<KeyType, ValueType> • Common Methods • clear() containsKey(Object key) • containsValue(Object value) entrySet() • equals(Object o) get(Object key) • hashCode() isEmpty() • keySet() put(KeyType k, ValueType v) • remove(Object key) size() • values() – returns Collection<V> • Map Example

14. String/Character • Additional methods for String • matches(regular expression) • Example: answer.matches(“[Yy][Ee][Ss]”); • Static methods from the class Character • Character.toUpperClase(char) • Character.toLowerCase(char) • Example Code