Week 11 Tuesday. CS 400 Programming III

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1 CS 400 Programming III Week 11 Tuesday X-Team Exercise 4: due before 10pm this Monday April 16 th Timeout your JUnit tests (if public Timeout globaltimeout = Timeout.seconds(10); // 10 seconds max per method Team Project: Tournament-Bracket (D-Team 30pts) Milestone 1: due before 10pm Friday, April 20 th (A-Team 20pts) Milestone 2: due before 10pm Monday, April 23 rd (A-Team 100pts) Milestone 3: due before 10pm Thursday, May 3rd Read: Module 10 (links to Java 8 feature documentation) TODAY in Lecture: make and Makefiles explained with examples X-Team Exercise 4 COMPLETE YOUR WordProcessor.getWordStream() method before class and bring your code to lecture to help you answer Top Hat questions. Functional Interfaces (java.util.function.function) Lambda expressions Next Lecture More Streams o java.nio.file.files o java.nio.file.paths o java.nio.streams Copyright 2018 Deb Jim Skrentny CS 400 (S18): W11T - 1

2 CS 400 Programming III Makefile what is a makefile? a build utility what a build utility? a program that creates executables Are there other build utilities? shell scripts, ant, maven, gradle Steps 1. create a file named Makefile with targets and [TAB]rules 2. Run make [optional - with a target name] p1 Makefile (simple targets) main: javac *.java test: clean: java TestMaxPQ \rm *.class p2 Makefile (basics with JUnit) main: javac -g -cp.:/usr/share/java/junit4.jar *.java junit: clean: java -cp.:/usr/share/java/junit4.jar org.junit.runner.junitcore TestSearchTree \rm *.class p3 Makefile with command-line argument and output to a file make: javac -cp. *.java java -cp. AnalysisTest../data/data_details.txt > results.txt xlint: javac -Xlint:unchecked *.java clean: \rm *.class Copyright 2018 Deb Jim Skrentny CS 400 (S18): W11T - 2

3 p2 Makefile with variables and Java classpath example From: JFLAGS = -g JC = javac CP =.:/usr/share/java/junit4.jar.suffixes:.java.class compiles.java source into.class files.java.class: $(JC) $(JFLAGS) -cp $(CP) $*.java CLASSES = \ SearchTreeADT.java \ BalancedSearchTree.java \ TestSearchTree.java \ default: classes classes: $(CLASSES:.java=.class) make clean - removes all class files and permit new build of all clean: $(RM) *.class make junit - run the TestSearchTree JUnit test class junit: java -cp $(CP) org.junit.runner.junitcore TestSearchTree CS 400 Programming III make copy - use scp to copy p2 files from assignment directory to current directory CAUTION: this will overwrite existing files with same name in same directory without warning or chance to cancel copy TO USE: remove echo from start of scp command replace cslogin with your CS login username copy: echo scp -r cslogin@best-linux.cs.wisc.edu:/p/course/cs400-deppeler/public/htmls/assignments/p2/files/*. Copyright 2018 Deb Jim Skrentny CS 400 (S18): W11T - 3

4 CS 400 Programming III DictionaryGraph: WordProcessor getwordstream() read contents of a file, given the filepath/filename return a Stream of words where each word has been: a. trimmed (of preceding and trailing whitespace) b. non-null and non-empty c. converted to UPPERCASE // TopHat: Declare wordstream as a Stream of String values Stream<String> wordstream = //TopHat: Write code to produce a Stream of lines read from filepath Files.lines(Paths.get(filepath)) // Complete this code to remove white space. map ( String::trim ) // Complete this code to ignore null and empty lines. filter ( x -> x!=null &&!x.equals("") ) // Complete this code to convert to upper case. map ( String::toUpperCase ) //Add code to return a stream return wordstream ; isadjacent() Copyright 2018 Deb Jim Skrentny CS 400 (S18): W11T - 4

5 Java 8: Functional Interfaces interface that defines exactly one abstract method may have static and default methods extends java.util.function.function not all interfaces with only one abstract method are FUNCTIONAL INTERFACES (eg. Comparable) CS 400 Programming III // not required public interface Comparator<T extends Event> extends EventListener { int compare(e obj1, E obj2) ; Use a Comparator to define how to compare instances whose types are not Comparable. Create and use a Comparator 1. define a class that implements Comparator (for your type) 2. create an instance of that class 3. use the instance in a method or expression that requires an instance Example: Use a comparator to sort Fish // define the Comparator class class FishComparator implements Comparator<Fish> public int compare(fish f1, Fish f2) { int dx = f1.x - f2.x; int dy = f1.y - f2.y; int dz = f1.z - f2.z; return dx==0? dy==0? dz : dy : dx; // Use an instance of the FishComparator to sort Fish List<Fish> fish = getrandomfish(10); FishComparator fishcomparator = new FishComparator(); Collections.sort( fish, fishcomparator ); Copyright 2018 Deb Jim Skrentny CS 400 (S18): W11T - 5

6 Anonymous Inner Classes CS 400 Programming III define a class don't give the class a name can give an instance created with it a name means we can only create an instance of our class in one place inside something (inner) // ANON INNER CLASS - class is anonymous, instance has a name static final Comparator<Fish> FISH_COMPARATOR = new Comparator<Fish>() public int compare(fish f1, Fish f2) { int dx = f1.x - f2.x; int dy = f1.y - f2.y; int dz = f1.z - f2.z; return dx==0? dy==0? dz : dy : dx; ; /** * Create and use a Comparator created as an ANONYMOUS INNER CLASS * * NOTE: FishComparator class is not needed for this example to work */ public static void example2_anonymous_inner_class() { List<Fish> fish = getrandomfish(10); System.out.println("not sorted: " + fish); Collections.sort(fish, ); // PUT ANONYMOUS INNER CLASS HERE new Comparator<Fish>() public int compare(fish f1, Fish f2) { int dx = f1.x - f2.x; int dy = f1.y - f2.y; int dz = f1.z - f2.z; return dx==0? dy==0? dz : dy : dx; System.out.println("after sort: " + fish); Copyright 2018 Deb Jim Skrentny CS 400 (S18): W11T - 6

7 CS 400 Programming III Java 8 Lambda Expressions Lambda Expressions create instances of functional interfaces use a L.E. when you need an instance of a functional interface type in only one place. the instance is not named the type of the instance is not named either the interface type is inferred by the target type for the instance. "L.E.s PASS BEHAVIOR not data" 1. Define a Functional Interface named ValueGenerator interface ValueGenerator { int getnextvalue(int prev); 2. Define a method that uses the functional interface ValueGenerator static int [] getsequence(valuegenerator vgen, int v0, int n) { int [] list = new int[n]; for (int i=0; i < n; i++) list[i] = v0 = vgen.getnextvalue(v0); return list; 3. Use a Lambda Expression to create instance & generate sequences public static void main(string [] args) { int[] s1 = getsequence( x ->{return x+1;, 0, 3 ); int[] s2 = getsequence( k ->{return k-1;, -3, 7 ); int[] s3 = getsequence( (v0)->{return (int)(math.random()*50)+v0;,0,5); System.out.println("seq1="+Arrays.toString(s1)); System.out.println("seq2="+Arrays.toString(s2)); System.out.println("seq3="+Arrays.toString(s3)); Copyright 2018 Deb Jim Skrentny CS 400 (S18): W11T - 7

8 Lambda Expression Fill-In-The-Blank (Summary) CS 400 Programming III lambda expressions must be associated with a functional interface functional interface defines a target or context for lambda expression lambda expression defines the behavior of the function for that instance convenient (shorter syntax) for when a single unnamed instance is needed (e.g. EventHandler in JavaFX) Streams Allows you to process data in a declarative way. Bonus: can leverage multi-core processors w/o writing multi-threaded code Example: get all lines of file into a list non-empty, trimmed, upper-case Strings Get Word List from a File In Java 7: get word list List<String> wordlist = new ArrayList<String>(); File file = new File(filename); Scanner filescnr = new Scanner(file); while ( filescnr.hasnextline() ) { String line = filescnr.nextline(); if ( line!= null &&! line.equals("")) { wordlist.add(line.trim().touppercase()); In Java 8: WordProcessor.getWordStream() Stream<String> = Files.lines(Paths.get(filepath)) // get lines from the file.filter( x -> x!= null && x!= "" ) // keep non empty lines.map(string::tostring) // convert to String.map(String::trim) // trim whitespace from start and end.map(string::touppercase); // convert to upper case Copyright 2018 Deb Jim Skrentny CS 400 (S18): W11T - 8