Department of Civil and Environmental Engineering, Spring Semester, ENCE 688R: Midterm Exam: 1 1/2 Hours, Open Book and Open Notes

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1 Department of Civil and Environmental Engineering, Spring Semester, 2016 ENCE 688R: Midterm Exam: 1 1/2 Hours, Open Book and Open Notes Name : Question Points Score Total 100 1

2 Question 1: 30 points This question covers basic Java programming. Figure 1 shows a 10cm by 5cm sheet of metal that will be folded into a small open box. 5 cm x cm 10 cm Figure 1: Open box folded from a rectangular sheet of metal. The following program computes and prints the surface area and volume as a function of the box height x. /* * ================================================================== * FoldedBox.java: Compute the surface area and volume of an * open box cut from a metal sheet 5 cm by 10 cm. * * Written By: Mark Austin March 2016 * ================================================================== */ import java.lang.math; public class FoldedBox { public static void main( String args[] ) { float farea; float fvolume; float MinVolume = 0.0f; float MaxVolume = 0.0f; float MinArea = 0.0f; float MaxArea = 0.0f; // Print header and setup table... System.out.println("Surface Area and Volume of Folded Open Box"); System.out.println(" "); System.out.println(""); System.out.println(" X Area Volume"); System.out.println(" "); 2

3 // Loop over side lengths... for ( float fx = 0.0f; fx <= 2.5; fx = fx f ) { // Compute area and volume farea = surfacearea(fx); fvolume = boxvolume(fx); // Check for new min and maximum. if(fx == 0.0) { MinArea = MaxArea = farea; MinVolume = MaxVolume = fvolume; else { MinArea = Math.min ( MinArea, farea ); MaxArea = Math.max ( MaxArea, farea ); MinVolume = Math.min ( MinVolume, fvolume ); MaxVolume = Math.max ( MaxVolume, fvolume ); // Format and print results. System.out.printf(" %4.2f %9.2f %11.2f\n", fx, farea, fvolume); // Print max and min values. System.out.println(" "); System.out.println(""); System.out.println("Minimum Surface Area = " + MinArea ); System.out.println("Maximum Surface Area = " + MaxArea ); System.out.println("Minimum Volume = " + MinVolume ); System.out.println("Maximum Volume = " + MaxVolume ); /* * =============================================== * Method surfacearea() : compute box surface area * * Input : fx * Output : float farea * =============================================== */ static float surfacearea( float fx ) { return (float) (5.0* *fx*fx); /* * =============================================== * Method boxvolume() : compute box volume * * Input : fx * Output : float fvolume 3

4 * =============================================== */ static float boxvolume(float fx) { return (float) ((5.0-2*fx)*(10.0-2*fx)*fx); The formatted output is as follows: prompt >> prompt >> java FoldedBox Surface Area and Volume of Folded Open Box X Area Volume Minimum Surface Area = 25.0 Maximum Surface Area = 50.0 Minimum Volume = 0.0 Maximum Volume = 24.0 prompt >> exit Please look at the source code carefully, and then answer the following questions: [1a] (3 pts). What are the two types of comment statement used in the FoldedBox program? 4

5 [1b] (3 pts). What does the line of code import java.lang.math; do? And why is it included in this program? [1c] (3 pts). Suppose that the statement of code float MinVolume = 0.0f; is changed to float MinVolume = 0.0; and then the program is compiled. What will the Java compiler complain about? [1d] (3 pts). List the methods whose source code is contained within FoldedBox. 5

6 [1e] (4 pts). The program execution will begin in the method main.. What are the purposes of each keyword in the line: public static void main ( String [] args ) {... [1f] (6 pts). Construct a table showing the values of fvolume, MinVolume, and MaxVolume as the for loop increments from fx = 0.0f to 2.5 in increments of

7 [1g] (3 pts). Briefly explain the purpose of the terms %4.2f, %9.2f and %11.2f in System.out.printf(" %4.2f %9.2f %11.2f\n", fx, farea, fvolume); [1h] (3 pts). What is the purpose of the keyword static in static float surfacearea( float fx ) {... [1i] (2 pts). What are the files that will exist before and after compilation? 7

8 Question 2: 40 points This question covers Java Programming with abstract classes and array lists. Absract class Shape Location Rectangle Circle Triangle Figure 2: Relationship among the classes Shape, Location, Rectangle, Circle and Triangle. Figure 2 shows the relationship among the classes Shape, Location, Rectangle, Circle and Triangle. The following code is a snapshot of the actual implementation that only covers Shape.java, Location.java, Rectangle.java and the test program defined in EngineeringProperties.java. Shape.java. The details of Shape.java are as follows: public abstract class Shape { Location c = new Location(); public abstract double getx(); public abstract double gety(); public abstract String tostring(); public abstract double perimeter(); public abstract double area(); Location.java. The (x,y) coordinates of a point are handled in Location.java. public class Location { double dx, dy; Rectangle.java. The details of Rectangle.java are as follows: public class Rectangle extends Shape { double dside1, dside2; public Rectangle ( double dside1, double dside2, double dx, double dy ) { this.dside1 = dside1; this.dside2 = dside2; 8

9 c.dx = dx; c.dy = dy; public String tostring() { return "Rectangle : Side1 = " + dside1 + " Side2 = " + dside2 ; public double perimeter() { return 2.0*(dSide1 + dside2); public double area() { return dside1*dside2; public double getx() { return c.dx; public double gety() { return c.dy; EngineeringProperties.java. import java.util.arraylist; import java.util.iterator; import java.util.list; public class EngineeringProperties { public static void main ( String args[] ) { // Create and initialize a grid of ten shapes List shapes = new ArrayList(); Shape s0 = new Rectangle( 0.25, 0.25, 0.0, 2.0 ); Shape s1 = new Rectangle( 0.25, 0.25, 1.0, 1.0 ); // Add shapes to the array list... shapes.add( s0 ); shapes.add( s1 ); // Compute and print total shape area... double darea = 0.0; for (int ii = 1; ii <= shapes.size(); ii = ii + 1) { Shape s = (Shape) shapes.get(ii-1); darea = darea + s.area(); System.out.println(""); System.out.printf("Total Area = %10.2f\n", darea ); System.out.println(" "); 9

10 Please look at the source code carefully and answer the questions that follow: [2a] (5 pts). Write a main() method for Rectangle.java. The method should allocate and initialize an object of type Rectangle and then print its contents. Now suppose that the new version of Rectangle.java (containing your main() method) is compiled without error. [2b] (3 pts). What command would you give to run the Rectangle program? (Please do not write: I d press the run button). [2c] (3 pts). What will the program output look like? 10

11 [2d] (5 pts). Draw and label a diagram showing the layout of memory produced by the statement: Rectangle ra = new Rectangle( 1.0, 1.0, 3.0, 4.0 ); Note: Make sure that you capture the relationship between Rectangle, Shape and Location. [2e] (4 pts). What is the purpose of the method tostring() in the statement? System.out.println( ra.tostring() ); 11

12 Now let s move onto Shape.java. [2f] (5 pts). List two ways in which an abstract class (e.g., Shape.java) differs from a regular class (e.g., Circle.java). [2g] (5 pts). Draw and label a diagram showing the layout of memory that occurs after the block of statements: List shapes = new ArrayList(); Shape s0 = new Rectangle( 0.25, 0.25, 0.0, 2.0 ); Shape s1 = new Rectangle( 0.25, 0.25, 1.0, 1.0 ); shapes.add( s0 ); shapes.add( s1 ); has finished. 12

13 [2h] (5 pts). The block of code: double darea = 0.0; for (int ii = 1; ii <= shapes.size(); ii = ii + 1) { Shape s = (Shape) shapes.get(ii-1); darea = darea + s.area(); walks along the arraylist and computes total area of the shapes. Construct a simple table to show the value of darea as a function of variable ii. [2i] (5 pts). Briefly indicated how you would modify the body of main() to take advantage of Java Generics. 13

14 Question 3: 30 points In this question we explore the modeling of many-to-many relationships between US states and their membership in geographical regions. Geographical Regions US States West Coast East Coast WA CA CO MD NY TX FL Southern States Figure 3: Schematic for US states and their membership in geographical regions. As a starting point, the right-hand side of Figure 3 shows a sampling of US states CA is an abbreviation for California, MD stands for Maryland, FL stands for Florida, and so forth. The left-hand side of Figure 3 shows how groups of states can be bundled into geographical regions. For example, CA and WA belong to the West Coast region; Maryland and Florida are part of the East Coast region; Texas and Florida belong to the Southern States region. A many-to-many relationship exists between geographical regions and US states because regions contain multiple states and, conversely, states such as Florida belong to multiple regions. Now let s assume that software for modeling the many-to-many relationship is contained into files, State.java and GeographicalRegion.java. A third file, SimUSA.java, creates state and geographical region objects, and then systematically assembles dependencies in the many-to-many relationship. File: State.java source code /* * ======================================================= * State.java; Create a "US state" object... * ======================================================= */ package geography; import java.util.collection; 14

15 import java.util.arraylist; import java.util.iterator; public class State { private String sname; private int ipopulation; // Collection of regions to which the state belongs. private Collection<GeographicalRegion> regions; // Constuctor method... public State( String sname ) { this.sname = sname; regions = new ArrayList<GeographicalRegion>(); // Set and get methods for the State name... public void setname( String sname ) { this.sname = sname; public String getname() { return sname; // Set and get methods for the State Population... public void setpopulation( int ipopulation ) { this.ipopulation = ipopulation; public int getpopulation() { return ipopulation; // Add a State to a Region... public void addgeographicalregion( GeographicalRegion region ) { // Add new region to states membership... if ( getgeographicalregions().contains(region) == false ) { getgeographicalregions().add(region); // Update list of states belonging to region... if ( region.getstates().contains(this) == false ) { region.getstates().add(this); 15

16 // Return collection of regions... public Collection<GeographicalRegion> getgeographicalregions() { return regions; // Create String representation of student object... public String tostring() { String s = "State: " + sname + "\n"; s = s + "Population: " + ipopulation + "\n"; s = s + "Regions: "; if ( regions.size() == 0 ) s = s + " none \n"; else { Iterator iterator1 = regions.iterator(); while ( iterator1.hasnext()!= false ) { GeographicalRegion r = (GeographicalRegion) iterator1.next(); s = s + r.getname() + " "; s = s + "\n"; return s; File: GeographicalRegion.java source code /* * ====================================================================== * GeographicalRegion.java; Create simple model of a geographical region. * ====================================================================== */ package geography; import java.util.arraylist; import java.util.collection; import java.util.iterator; public class GeographicalRegion { private String sname; // Setup collection of states... private Collection<State> states; 16

17 // Constructor method... public GeographicalRegion(){ states = new ArrayList<State>(); // Methods to deal with the region name... public String getname() { return sname; public void setname(string regionname ) { this.sname = regionname; // Add a state to the geographical region... public void addstate( State st ) { if ( getstates().contains( st ) == false ) { getstates().add( st ); // Update regions on the state side... if ( st.getgeographicalregions().contains(this) == false ) { st.getgeographicalregions().add(this); public Collection<State> getstates() { return states; public void setstate( Collection<State> states ) { this.states = states; // Compute total population of the geographical region... public int getpopulation() { int ipopulation = 0;... Details of source code removed... See Question [3f]... return ipopulation; // Create a String representation for the geographical region... public String tostring() { String s = "Geographical Region: " + sname + "\n"; s = s + "States: "; if ( states.size() == 0 ) 17

18 s = s + " none \n"; else { Iterator iterator1 = states.iterator(); while ( iterator1.hasnext()!= false ) { State st = (State) iterator1.next(); s = s + st.getname() + " "; s = s + "\n"; s = s + "Population: " + getpopulation() + "\n"; return s; File: SimUSA.java source code /* * ======================================================================== * SimUSA.java: Simulate many-to-many relationships between US states * and the geographical regions to which they belong. * ======================================================================== */ package demo; import geography.*; public class SimUSA { public static void main( String[] args ) { // [a]: Create objects for US states... State md = new State( "MD" ); md.setpopulation( 5 ); State fl = new State( "FL" ); fl.setpopulation( 10 ); State ca = new State( "CA" ); ca.setpopulation( 40 ); State tx = new State( "TX" ); tx.setpopulation( 30 ); // [b]: Add states to the East Coast Region... GeographicalRegion east = new GeographicalRegion(); east.setname("east Coast"); east.addstate( md ); east.addstate( fl ); 18

19 // [c]: Add states to the Southern Region... GeographicalRegion south = new GeographicalRegion(); south.setname("southern States"); south.addstate( tx ); south.addstate( fl ); // [d]: Print details of state-region assocations... System.out.println( "Part 1: Summary of State/Geographical Region Associations" ); System.out.println( "=========================================================" ); System.out.println( md ); System.out.println( fl ); // [e]: Print details of region-state assocations... System.out.println( "Part 2: Summary of Geographical Region/State Associations" ); System.out.println( "=========================================================" ); System.out.println( east ); System.out.println( south ); The script of program input and output is as follows: prompt >> ant run02 Buildfile: /Users/austin/ence688r.d/exam-code.d/build.xml compile: [javac] /Users/austin/ence688r.d/exam-code.d/build.xml:9: run02: [java] Part 1: Summary of State/Geographical Region Associations [java] ========================================================= [java] State: MD [java] Population: 5 [java] Regions: East Coast [java] [java] State: FL [java] Population: 10 [java] Regions: East Coast Southern States [java] [java] Part 2: Summary of Geographical Region/State Associations [java] ========================================================= [java] Geographical Region: East Coast [java] States: MD FL [java] Population: 15 [java] 19

20 [java] Geographical Region: Southern States [java] States: TX FL [java] Population: 40 [java] BUILD SUCCESSFUL Total time: 1 second prompt >> exit Please look at the source code carefully and answer the questions that follow: [3a] (5 pts). Draw and label a diagram that shows the organizational arrangement of java packages and user-defined java source code files. 20

21 [3b] (5 pts). Draw and label a diagram that shows the relationship among the State, GeographicalRegion and SimUSA classes. [3c] (5 pts). Draw and label a diagram showing the layout of memory generated by sections [a] through [c] of SimUSA.java. 21

22 [3d] (5 pts). What is the purpose of the syntax <GeographicalRegion> in the statement: private Collection<GeographicalRegion> regions; [3e] (5 pts). Briefly explain the way in which the classes State and GeographicalRegion would change if the many-to-many relationships were implemented as HashSets instead of ArrayLists. 22

23 [3f] (5 pts). Write the code missing from the method getpopulation() in GeographicalRegion.java, i.e, public int getpopulation() { int ipopulation = 0;... fill in the missing details here... return ipopulation; 23