CS 0401 Fall 2017 Quiz 2 Version A SOLUTIONS. logical size of an ArrayList is the number of items being stored in the array.

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1 CS 0401 Fall 2017 Quiz 2 Version A SOLUTIONS 1) Fill in the Blanks (14 points 2 points each). Provide the MOST appropriate answers. If choices are given in square brackets, select one of the choices. a) Consider the following: Given an array A, for all i and j, if i < j, then A[i] > A[j]. This is defining a sort in [ascending, descending] descending order. b) The physical size of an ArrayList is the length of the underlying array and the logical size of an ArrayList is the number of items being stored in the array. c) The Java classes Integer, Float, etc. are called wrapper classes and are used to allow the primitive types to be accessed as objects. d) Instance data in Java declared to be protected can be directly accessed within its own class, any subclasses of that class and the package in which that class is located. e) Composition gives a has a [is a, has a] relationship between the new and old classes while inheritance gives a is a [is a, has a] relationship between the new and old classes. f) Ad hoc polymorphism utilizes method overloading [overloading, overriding] whereas subclassing polymorphism utilizes method overriding [overloading, overriding] g) The SortAll.selectionSort() method that we discussed in lecture will sort an array of any class that implements the Comparable interface. 2) True / False (12 points 2 points each). Correct false statements for full credit. a) To "increase the size" of a full array in Java we must actually make a new, larger array and copy the data from the old array to the new one. True b) The binary search algorithm of an array with N items in the worst case requires all N items to be compared. False it requires at most ~lgn items to be compared c) The declaration: String [] A = new String[10]; will create 10 String objects. False it will create 0 String objects. d) In a Java Person class, the age of the Person should be an instance variable since it is a fundamental attribute of the Person. False it should be a method since age changes with time. e) Consider classes Foo and SubFoo, where SubFoo is a subclass of Foo. The Java statement: SubFoo S = new Foo(); is legal False isa is one way f) Consider classes Foo and SubFoo, where SubFoo is a subclass of Foo. The Java statement: Foo F = new SubFoo(); is legal True

2 3) Trace (14 points). Consider the two classes on this page and the Trace1A program on the next page. Give all output, in the correct order and format, produced by execution of the Trace1A Java program. Clearly indicate your output by drawing a box around it. public class Outer public StringBuilder outerstr; public Inner outerobj; public Outer(String s1, String s2) outerstr = new StringBuilder(s1); outerobj = new Inner(s2); public Outer(Outer old) outerstr = new StringBuilder(old.outerStr); outerobj = new Inner(old.outerObj); return outerstr + ", " + outerobj.tostring(); public void mutate(string m1, String m2) outerstr.append(m1); outerobj.mutate(m2); public class Inner public StringBuilder innerstr; public Inner(String s) innerstr = new StringBuilder(s); public Inner(Inner old) innerstr = old.innerstr; return innerstr.tostring(); public void mutate(string m) innerstr.append(m);

3 public class Trace1A public static void main(string [] args) Outer data = new Outer("one", "first"); Outer copy = new Outer(data); Outer copy2 = new Outer(copy); data.mutate("two", "second"); copy.mutate("three", "third"); Output: Orig: one, first Copy: one, first Copy2: one, first Orig: onetwo, firstsecond Copy: one, firstsecond Copy2: one, firstsecond Orig: onetwo, firstsecondthird Copy: onethree, firstsecondthird Copy2: one, firstsecondthird

4 4) Trace (10 points). Consider the three classes on this page and the Trace2A program on the next page. Give all output, in the correct order and format, produced by execution of the Trace2A program. Clearly indicate your output by drawing a box around it. public class SuperClass protected String A; public SuperClass(String x) A = new String(x); return "I am: " + A; public void setname(string newname) A = new String(newName); public class MidClass extends SuperClass protected String B; public MidClass(String x, String y) super(x); B = new String(y); return super.tostring() + B; public class SubClass extends MidClass private String C; public SubClass(String x, String y, String z) super(x, y); C = new String(z); return super.tostring() + C; public void setname(string newname) super.setname(newname); C = new String(newName);

5 public class Trace2A public static void main(string [] args) SuperClass [] Arr = new SuperClass[3]; Arr[0] = new SuperClass("Vizzini"); Arr[1] = new MidClass("Count", "Rugen"); Arr[2] = new SubClass("Dread", "Pirate", "Roberts"); for (SuperClass S: Arr) System.out.println(S.toString()); Arr[0].setName("Fezzik"); Arr[1].setName("Evil"); Arr[2].setName("Westley"); for (SuperClass S: Arr) System.out.println(S.toString()); Output: I am: Vizzini I am: CountRugen I am: DreadPirateRoberts I am: Fezzik I am: EvilRugen I am: WestleyPirateWestley