Canterbury QuestionBank

Which statement produces a compilation error?

class A extends M implements I {// code was removed}

class B extends N implements I {// code was removed}

class A extends M implements I, L, J {// code was removed}

class A extends M implements I {// code was removed}

Which of the following choices cannot be another constructor for academic class?

class personnel{

      String name, ID;

      char qualificationCode;

      public personnel(String n, String i, char q){

           name = n;

          >

           qualificationCode = q;

      }

      public personnel (){

           name = null;

          >

           qualificationCode = ' ';

      }

}

class academic extends personnel{

             int teachingHours;

            public academic(String n, String i, char q, int t){

                  super(n,i,q);

                  teachingHours = t;

            }

            public academic(int t){

                 super(null, null, ' ');

                  teachingHours = t;

           }

}

public academic(){

           this (null, null, ' ', 0);

}

public academic(){

          name = null;

         >

         qualificationCode = ' ';

         teachingHours = 0;

}

public academic(){

       super(null, null, ' ');

       teachingHours = 0;

}

Where in this code a compiler error is reported and why?

1  class pen{

2         char colorCode;

3  }

4  public class penCounter {

5         public static void main(String[] arg){

6                    int numberOfPen;

7                    pen myPen = new pen();

8                   System.out.println(myPen.colorCode + numberOfPen);

9         }

10}

line 8, colorCode has not been initialized.

line 6, numberOfPen has not been initialized.

line 2, colorCode has not been initialized.

What will be the outputted?

class A{

     int firstMethod(int input){

     return input*2;

     }

}

class B extends A{

     int firstMethod(int input){

     super.firstMethod(input);

     return input*2;

    }

}

class C extends B{

    int firstMethod(int input){

    return super.firstMethod(input)* 2;

    }

}

public class test {

    public static void main(String[] arg){

        C myObject = new C();

        System.out.println(myObject.firstMethod(2));

   }

}

4

16

32

What will be outputted?

class A{

      int firstMethod(int input){

           return input+2;

     }

}

class B extends A{

}

class C extends B{

     int firstMethod(int input){

          return input-2;

     }

}

public class test {

     public static void main(String[] arg){

          B myObject = new B();

          System.out.println(myObject.firstMethod(2));

     }

}

0

2

Compiler Error

Which sentence is NOT correct?

If a class has only private constructors, it cannot be extended.

If a class is final, it cannot be extended.

If a class is public, it is extendable anywhere.

Which part of the following code will produce a compiler error if we know class cat extends a class called animal and both of the classes have a method called makeNoise and class cat has a method called showFood.

1     animal mydog = new animal();

2     mydog.makeNoise();

3     animal mycat = new cat();

4     mycat.makeNoise();

5     mycat.showFood();

line 3, new cat should be changed to new animal.

line 3, animal should be changed to cat.

line 4, makeNoise has not been recognized by mycat

Which on these four following definitions is not allowed?

abstract class first{

        void firstMethod(){}

}

abstract class second{

         abstract void secondMethod();

}

class third {

        abstract void thirdMethod();

}

class fourth{

        void fourthMethod(){}

}

first

second

fourth

Which option is NOT an alternative solution for the bug that exists in this code?

class shape{

        float area;

        public shape( float a){

              area = a;

        }

}

class square extends shape{

         float side;

         public square (float s){

                   side = s;

        }

}

square constructor should call a super constructor explicitly.

Class shape must have a null constructor.

shape constructor should be removed.

Considering the following code, which of the choices are wrong when access to ID is desired?

class N{

        private int ID;

        public void setID(int id){

                  >

        }

        public int getID(){

                  return ID;

        }

}

if we had the following in class N

N n = new N();

System.out.print(n.ID);

If we had the following in class N

System.out.print(ID);

If we had the following in another class but the same package as N

N n = new N();

System.out.print(n.getID());

What will be printed?

class A{

        protected void A_Method(){

        System.out.println ("This is the first A_Method");

        }

}

class B extends A{

         protected void A_Method(){

         System.out.print ("This is the second A_Method");

         }

}

class C extends B{

         protected void A_Method(){

         System.out.print ("This is the third A_Method");

         }

}

public class test {

        public static void main(String[] args){

        A [] objects = new A[3];

        objects[0]= new A();

        objects[1]= new B();

        objects[2]= new C();

        objects[1].A_Method();

       }

}

This is the first A_Method

This is the third A_Method

Nothing, this is an error.

Java remembers which object (subtype) has been inserted into the array because of polymorphism.

What is wrong with this code?

final class A{

}

class B extends A{

}

Class B is not public.

Class A is not public.

There are no instance variables and methods defined for these classes.

How many object references will be created after initializing the following array?

String [][] names = new String [3][2];

3

2

6

What would be outputted?

String s_1 = "Hello";

String s_2 = "World";

System.out.format("%-7S %7s", s_1,s_2);

Hello         World

     Hello World

     HELLO World

How many times the capacity of the vector in following code changes?

Vector<Integer> intVect = new Vector<Integer>(10,2);

for (int i = 0; i <40; i++)

     intVect.add(i);

2

5

30

In a program 5 objects are created initially and inserted into a vector. These objects increase to 64 during the execution of the program. Each time 8 objects is added to the vector except the last time in which 3 objects is added. Which of the following definition results in better performance in terms of execution time and allocated space at the end?

Vector<Object> objectVect = new Vector<Object>(5,8);

Vector<Object> objectVect = new Vector<Object>(8,5);

Vector<Object> objectVect = new Vector<Object>(5);

Which of the following variables are object references?

public class firstClass {

         double[] doubleArray = {2.3, 3.4};

         public static void main(String[] args) {

               int width = 250;

              Color col = new Color(88,34,200);

         }

}

width, doubleArray

col, width

col, width, doubleArray

What change should be made to correct the code?

String returnValue = "";

try {

         BufferedReader d = new BufferedReader(new InputStreamReader(System.in));

         String userInput = new String(d.readLine());

         returnValue = userInput;

}

Need to insert finally.

Need to insert catch.

Need to remove try.

What would you put in the blank areas to let the following code read some integer data from console?

Scanner sc = new Scanner(_______________);

int intValue ;

while ((intValue = _______________)!= -1)

          System.out.println(intValue);

nothing, leave it blank , sc.nextInt()

nothing, leave it blank , sc.hasNextInt()

System.in , sc.hasNextInt()

What will be printed by the following code if in.txt includes two sentences which have been inserted in two separate lines?

try {

          inputStream = new FileReader("in.txt");

          int c;

          while ((c = inputStream.read()) != -1)

                 System.out.println((char)c);

} finally {

         if (inputStream != null)

                 inputStream.close();

}

A sequence of integers that represents the unicode of characters that form the text.

The first line in in.txt.

The whole text in in.txt.

What will be outputted?

String input = "Home               is                             where the heart is";

Scanner sc_input = new Scanner(input).useDelimiter("\\s*is\\s*");

while (sc_input.hasNext())

            System.out.println(sc_input.next());

Home

is

where

the

heart

is

Home

is

Where the heart

is

Home

where

the

heart

What will be the output?

class Pen{

       float hight;

       public Pen(){

           hight = 0;

       }

       public Pen ( float h){

           hight = h;

       }

}

class Pencil extends Pen{

      String type;

      public Pencil(){

           type = null;

     }

     public Pencil (String t){

           type = t;

     }

}

public class test {

      public static void main(String[] arg){

              Pen mypen = new Pen(10);

             System.out.print(mypen.hight+ " ");

             Pencil mypencil = new Pencil("HB");

             System.out.println(mypencil.hight + " "+ mypencil.type);

      }

}

10.0 10.0 HB

A compiler error

A runtime error

What will be the output?

class Pen{

         float hight;

        public Pen ( float h){

              hight = h;

       }

}

class Pencil extends Pen{

       String type;

       public Pencil(){

            type = null;

       }

      public Pencil (String t){

           type = t;

     }

}

public class test {

      public static void main(String[] arg){

           Pen mypen = new Pen(10);

           System.out.print(mypen.hight+ " ");

           Pencil mypencil = new Pencil("HB");

           System.out.println(mypencil.hight + " "+ mypencil.type);

      }

}

10.0 0.0 HB

10.0 10.0 HB

A runtime error

Which option is NOT a correct solution to handle an exception if we know that NumberException is a user defined exception?

public static int testNumber(int x) throws NumberException{

       if (x >= 12)

                 throw new NumberException("This is my created exception message");

      return x;

}

public static int testNumber(int x) throws NumberException{

    try{

        if (x >= 12)

             throw new NumberException("This is my created exception message");

   }

   finally{}

   return x;

}

public static int testNumber(int x) {

     try{

          if (x >= 12) throw new NumberException();

    }

    catch (NumberException e){

        e.printStackTrace();

   }

   finally{}

   return x;

}

2. Consider the following class definition:

public class SillyTestClass {
   public SillyTestClass(int x, int y) {
      System.out.println(y);
   }
   public SillyTestClass(String string1, String string2) {
      System.out.println(string2);
   }
   public static void main (String [ ] args) {
      SillyTestClass app = new SillyTestClass(20, “Try this!”);
   }
}

Which of the following is the most accurate statement about this code?

The class definition won't compile, because it has two constructors.

The class definition won't compile, because two constructors have the same number of parameters.

It will compile, and the output when the main method is executed will be: 20

It will compile, and the output when the main method is executed will be: Try this!

Answer A is wrong because Java programs can have more than one constructor. Answer B is wrong because a variation between the type of the parameters is also sufficient. Answers D and E are wrong because the program won't compile or execute. Answer C identifies the problem.

The code fragment given above was intended to read values until a negative value was read and then to print the product of the positive values read. Unfortunately, it does not work.

1.  Scanner kbd = new Scanner(System.in);
2.  int x, product;
3.  product = 0;
4.  x = kbd.nextInt();
5.  while (x >= 0) {
6.     if (x > 0) {
7.        product *= x;
8.     }
9.     x = kbd.nextInt();
10. }
11. System.out.println(product);

Which of the following best describes the error that prevents the code from computing the correct answer?

 Variable x is not initialized correctly.

The loop is executed one too many times.

The loop is executed one two few times.

None of the above.

Because the variable product is initialized to 0 instead of 1, the answer will always be 0. 

Using the information in the above UML diagram, if sporty is an instance of Car, what gets called if you execute sporty.move()?

The move method defined in Vehicle

The move method defined in PeopleHauler

All of the above

None of the above

Since the diagram indicates that there is a move method defined in Car, and sporty is an instance of Car, then that one is the one executed.

Using the information in the UML diagram above, suppose the move method of OilTanker has the line super.move(). Which move method does that refer to?

The move method defined in Vehicle  

The move method defined in PeopleHauler 

The move method defined in Car

All of the above

super.move() in OilTanker refers to the move method that would be found starting from its superclass, which is Truck, which is not given as an option.

Using the information in the UML diagram above, suppose some method of Truck has the line super.move(). Which of these is true?

The move method defined in Truck is executed when that line is executed.

The move method defined in Vehicle is executed when that line is executed.

It depends on whether move() is defined in Vehicle’s superclass

None of the above

super.move() refers to the move method defined in Vehicle, and since Vehicle's move method is abstract this will not compile, even if an ancestor of Vehicle defines a move() method that Vehicle would presumably inherit.

Using the information in the UML diagram above, suppose we execute the following Java statements:

     Vehicle vehicle = new OilTanker(2500);
     vehicle.move();

which definition of move will be executed?

The one defined in Truck

The one defined in Vehicle

The one defined in PeopleHauler

The code will not work

Since the actual type of vehicle is OilTanker, and since move is an appropriate method for instances of Vehicle, which is vehicle's declared type,  the move method invocation will work, and will be the one defined in OilTanker

Consider the following code:

   public int examMethod(int n) {
      if (n == 1) return 1;
      else if (n > 1) return (n + this.examMethod(n-1));
   }

What is the purpose of examMethod?

to compute fibonacci(n)

to compute factorial(n)

none of the above

The method returns 1 if n is 1, 2+1 if n is 2, 3+2+1 if n is 3, etc. In other words, it computes the sum of the integers from 1 to n (answer C).

Consider the following method:

public int examMethod(int n) {
   if (n == 1) return 1;
   else return (n + this.examMethod(n-1));
}

Which of the following inputs will cause a non-terminating recursion?

1

20

30,000

None of the above

The base case for this recursion is n == 1. If n is 1, the recursion is done. If n is 20, then the value of n will be reduced by 1 with each recursive call (examMethod(19), examMethod(18), etc.), the value of n will finally reach 1, and the recursion will end. Similarly if n is 30,000.

But if n is 0 to begin with, then the next recursive call will be to examMethod(-1), then examMethod(-2), etc. The value of n will never reach the base case, and the method will (in theory) never terminate. 

Using the information in the UML diagram above, suppose we execute the following Java statements:

     PeopleHauler pM = new Car();
     pM.move();

which definition of move will be executed?

The one defined in PeopleHauler

The one defined in Vehicle

The one defined in Truck

None of the above

The actual type of pM is Car.  Since the declared type of pM is PeopleMover, an interface, move is an appropriate method call for pM since it is in the interface.  The definition used will be the one in the actual type,  Car.

Consider the following Java interface definition:

public interface Mover {
   public int getX();
   public int getY();
   public void setLocation(int x, int y);
}

Which of the following is a correct implementation of the Mover interface?

public class CartoonCharacter implements Mover{
   private int x, y;
   public int getX;
   public int getY;
   public void setLocation;

}

public class CartoonCharacter implements Mover{
   private int x, y;
   public int getX();
   public int getY();
   public void setLocation(int x, int y);

}

public class CartoonCharacter implements Mover{
   private int x, y;
   public int getX() {
      // code for method body
   }
   public int getY() {
      // code for method body
   }

}

public class CartoonCharacter implements Mover{
   private int x, y;
   public int getX() {   
      // code for method body
   }
   public int getY() {
      // code for method body
   }
   public int setLocation(int x, int y){
      // code for method body
   }
}

Choice A is wrong because it doesn't include parameter lists or implementations of any of the methods required by the interface.

Choice B is wrong because it doesn't include implementations of the methods on the list. 

Choice C is wrong because it implements some but not all of the interface methods. 

Choice E is wrong because the method signatures do not match those in the interface.

Choice D is the correct answer, because it's the only one where the required methods are all implemented, and their signatures match 

NOTE: There is no appropriate topic for this question in the list. Suggestion: TopicSimon-interfaces-Java

Consider the following Java interface:

public interface Mover {
   public int getX();
   public int getY();
   public void setLocation(int x, int y);
}

Choose the best description of the following implementation of the Mover interface:

public class CartoonCharacter implements Mover{
   public int getX;
   public int getY;
   public void setLocation;
}

The implementation is correct, because it includes all the required methods and their return types are correct.

The implementation is incorrect, because it doesn't include the method parameter types.

The implementation is incorrect, because it doesn't include implementations of the methods.

To implement a Java interface, a class must define all the methods required by the interface (or declare itself abstract).

NOTE: There is no appropriate topic for this question. Suggestion: TopicSimon-Interface-Java. 

1. What is the value of the following Java arithmetic expression?

                            4 * 3 + 6 / 4

4

4.5

9

13.5

This question addresses two points: first, operator precedence (multiplication and division are both done before addition) and second, integer division. Answer A is wrong about operator precedence: the answer you get if you apply the operators in order from left to right. Answer B makes the same mistake and is also wrong about integer division. Answer D is the answer you get if you assume that addition has a higher precedence than the other two operations. Answer E gets the operator precedence right, but is wrong about integer division. Answer C is the only one that has both right.

What is the maximum result of computing X % 7, where all we know about X is that it is a positive integer?

0

1

7

There is not enough information in the question description to answer.

% is the modular division operation, which perform division and returns the remainder.  For example, 7 % 7 is 0, since 7 goes into 7 once with a remainder of 0.  8 % 7 is 1, since 7 goes into 8 with a remainder of 1.  Similarly, 13 % 7 is 6, while 14 % 7 is again 0, since 7 goes into 14 twice with no remainder.  If you mod a positive integer by N, the maximum result is N-1.

Which sentence is not correct regarding exception handling in java?

A method can throw more than one exception.

You can have several catch statement for one try.

Statements inside catch are never run unless an exception happens.

What will be outputted?

int c = 1;

int result = 10;

result += ++c;

System.out.print(result+ " "+ c);

11  2

12  1

11  1

Which of these following codes result the same?

1

if (mark =='A'){

    if (GPA > 3.5)

    x = 1;

}

else

    x = 2;

2

if (mark =='A')

    if (GPA > 3.5)

        x = 1;

    else

        x = 2;

3

if (mark =='A'){

    if (GPA > 3.5)

        x = 1;

   else

        x = 2;

}

1,2

1,3

1,2,3

What will be outputted?

int num = 3;

int counter = 1;

boolean condition = true;

while(condition){

    num+= counter++;

    if(num>10){

        condition=false;

        num+= ++counter;

    }

}

counter = 5 num = 16

counter = 5 num = 17

counter = 6 num = 18

What will be outputted?

int income = 30;

boolean condition1 = true, condition2 = true;

if(income < 100)

    if(income > 10)

        if(condition1){

            System.out.print("A");

            if(income < 20)

            System.out.print("B");

        }

        else

            System.out.print("C");

    if(!condition2){

        if(income > 50)

            System.out.print("D");

    }

    else

       System.out.print("E");

AC

ABC

ACE

Fill the gap in such a way that the odd number less than 10 and greater than zero is printed.

for (_________________________)

    System.out.println(i+1);

int i = 0; i <= 10; i= i+2

int i = 1; i < 10; i= i+2

int i = 1; i <= 10; i= i+2

What would be outputted?

char initial = 'a';

switch (initial){

case 'a':

         System.out.print("A");

case 'b':

         System.out.print("B");

default:

         System.out.print("C");

}

AB

BC

A

What will be outputted?

char initial = 'a';

switch (initial){

    case 'a':

            System.out.print("A");

    default:

            System.out.print("C");

             break;

     case 'b':

              System.out.print("B");

              break;

}

compiler error

A

ACB

What would be the value of sum at the end of executing this code?

int sum;

for (int i = 0; i < 2; i++)

    for (int j = 0; j < 5; j++ ){

        sum = i + j;

        if (sum > 5) break;

        else continue;

        System.out.print(sum);

}

Compiler error due to not initializing local variable.

6

5

To compute the following series, the following code will do the job. What will be the initial value of stat, fact and sum respectively?

-X + X3/3! - X5/5! + ...

for ( int i = 2; i <= n; i++){

    for (int j = 2*i -1; j > 2*i -3 ; j--){

        stat *=x;

        fact*= j;

    }

    p_f *= -1;

    sum += p_f* stat/fact;

1, x, 0

x, 1, 0

 -x, 1, x

Consider the following static method in Java:

public static int[] mystery(int[] arr, int x) {
  int a=0;
  for (int i=0; i<arr.length; i++) {
    if (arr[i] > x) {
      a++;
    }
  }
  int[] ar2=new int[a];
  int z=0;
  for (int i=0; i<arr.length; i++) {
    if (arr[i] > x) {
      ar2[z]=arr[i];
      z++;
    }
  }
  return ar2;
}

What will this function (static method) return when invoke with the array {1, 9, 3, 4, 9, 4, 5, 2, 7} and the integer 5?

{} (an empty array)

{9, 5, 7}

{9, 9, 5, 7}

It will throw ArrayIndesOutOfBoundsException

This method returns a new array that contains only the elements larger than the parameter x.

Consider the following interface definition:

public interface Mover {
   public int getX();
   public int getY();
   public void setLocation(int x, int y);
}

Choose the answer that best describes the following implementation of the Mover interface:

public class CartoonCharacter implements Mover {

   public int getX();

   public int getY();

   public void setLocation(int x, int y);

}

The implementation is correct, because it includes all the methods.

The implementation is correct, because the method names, return types, and parameter lists match the interface.

Both A and B. 

A class that implements a Java interface must define all the methods required by the interface (or declare itself abstract).

NOTE: There is no appropriate topic for this question. Suggestion: TopicSimon-Interface-Java.

Consider the following code:

if x >= 0:
    print (1)
elif x < 20:
    print(2)
else:
    print(3)
print(4)

For what values of x will 2 be among the values printed?

All values of x

None of the above

Although the condition of the elif is x<20, all values between 0 and 20 are subsumed (i.e. covered by) the first condition, x>=0.  So only values of x strictly less than 0 will result in 2 being printed.

What is printed when the following program runs?

public class Main {
  public static boolean getTrue() {
    System.out.print("T");
    return true;
  }

  public static boolean getFalse() {
    System.out.print("F");
    return false;
  }

  public static void main(String[] args) {
    getFalse() || getFalse();
  }
}

T

F

FT

Nothing is printed.

|| evaluates the left operand first. It's not true, so it checks the second.

What is printed when the following program runs?

public class Main {
  public static boolean getTrue() {
    System.out.print("T");
    return true;
  }

  public static boolean getFalse() {
    System.out.print("F");
    return false;
  }

  public static void main(String[] args) {
    getTrue() && getTrue();
  }
}

F

T

FT

Nothing is printed.

The first operand is true. && requires both be true, so we check the second, which is also true.

What is printed when the following program runs?

public class Main {
  public static boolean getTrue() {
    System.out.print("T");
    return true;
  }

  public static boolean getFalse() {
    System.out.print("F");
    return false;
  }

  public static void main(String[] args) {
    getTrue() && getFalse();
  }
}

T

TT

F

Nothing is printed.

The first operand is true. && requires both operands be true, so we evaluate the second, which is false.

What is printed when the following program runs?

public class Main {
  public static boolean getTrue() {
    System.out.print("T");
    return true;
  }

  public static boolean getFalse() {
    System.out.print("F");
    return false;
  }

  public static void main(String[] args) {
    getFalse() && getTrue();
  }
}

FT

T

FF

Nothing is printed.

The first operand is false. && requires both be true, so we don't bother to evaluate the second.

Consider the code

int i = 3;

int *p = &i;

Which of the following will print out “The value is 3.”?

printf("The value is %p", p);

printf("The value is %d", &i);

printf("The value is %d", &p);

The value of p will be the memory address of i -- to dereference p, we need to use *p.

Which of the following lines of code will correctly read in the two floats x and y?

scanf("%d%d", &x, &y);

scanf("&d&d", %x, %y);

scanf("&f&f", %x, %y);

Scanf requires pointers to x and y -- hence the ampersands. As x and y are floats, %f is used for both.

Kejun has the executable add that adds three command-line args together and prints the
result. He runs it like so:
./add 25 10 5

In his code, what is the value of argc?

0

1

2

3

./add is considered a command-line argument

After the assignment signal = ’abracadabra’, what is returned by signal[:5]?

’abraca’

’c’

An error

None of the above

This is a slice operation.  Slices in Python work with both lists and with Strings, and go up to but not including the limit.  Since the limit is 5, we get the first 5 characters (indexed 0 through 4).  Hence abrac

After the assignment signal = ’abracadabra’, what is returned by signal[-1:]?

'abracadabra'

''

an error

none of the above

Python actually allows negative indexes, which start counting from the back of a list or String.  However, the slice operation by default still only uses increasing indexes.  So, slicing [-1:] means to slice from the last character through the rest of the String (slice operations that leave out the upper boundary implicitly mean "slice to the end").

Ming is hashing the numbers 5, 99, 15, 25 and the hash function h(k) = k % 10. Which
collision resolution strategy did she use?

Linear probing

Quadratic probing

Rth probing, R = 2

Rth probing, R = 3

The 5 is one over from where it should be; the 15 is one over.

What is returned by ’A A Milne’ < ’A Linkletter’?

False

'A A Milne'

an error

none of the above

This is a lexicographic (i.e. alphabetic) comparison.  The first 2 characters of both strings are the same (i.e. 'A '), but for the third character, 'A' comes before 'L' so we return True.

What is printed when the following program runs?

public class Main {
  public static boolean getTrue() {
    System.out.print("T");
    return true;
  }

  public static boolean getFalse() {
    System.out.print("F");
    return false;
  }

  public static void main(String[] args) {
    getFalse() || getTrue();
  }
}

TF

T

F

Nothing is printed.

|| guarantees left-to-right evaluation, stopping at the first operand that is true.

Many English words have separate singular and plural forms, e.g., "dog" and "dogs." We are trying to write a method that properly pluralizes a word (though naively, by only adding an "s" at the end) if the count we have of that word is not 1. If the count is 1, we leave the word as is. Which of the following proposed solutions does not meet this specification?

String getCounted(String singular, int count) {
  if (count != 1) {
    return singular + "s";
  } else {
    return singular;
  }
}

String getCounted(String singular, int count) {
  String quantified = singular;
  if (count != 1) {
    quantified = quantified + "s";
  }
  return quantified;
}

String getCounted(String singular, int count) {
  if (count == 1) {
    return singular;
  } else {
    String plural = singular + "s";
    return plural;
  }
}

String getCounted(String singular, int count) {
  if (count != 1) {
    singular += "s";
  }
  return singular;
}

Suffix is initialized to null. The concatenation of singular and suffix does not produce the desired behavior.

Consider the following Python code:

if x >= 0:
    print (1)
elif x < 20:
    print(2)
else:
    print(3)
print(4)

For what integer values of x will 1 be among the values printed?

All values of x

None of the above

Clearly x must be greather than or equal to 0 to for 1 to be printed.

Consider the following Python code:

if x >= 0:
    print (1)
elif x < 20:
    print(2)
else:
    print(3)
print(4)

For what integer values of x will 3 be amont the values printed?

x < 0

x >= 0

x < 20

All values of x

It's not possible to get 3 to print.  This is because all possible values of x are covered by if x>=0 and x<20.  This creates a range that includes all possible values of x, since any number is either >=0 or < 20.

Consider the following Python code:

if x >= 0:

    print 1

elif x < 20:

    print 2

else:

    print 3

print 4

For what values of x will 4 be among the values printed?

x < 0

x >= 0

x >= 20

None of the above

The statement that prints 4 is NOT part of the if expression; thus it will be preinted regardless of what happens with the loop

Converting a value from one type to another sometimes requires an explicit cast and sometimes does not. Which of the following conversions and lines of reasoning explains how to convert a double d to an int i?

i = d. No explicit cast is necessary because if the conversion isn't valid, an exception is thrown.

i = (int) d. An explicit cast is needed to round d to the nearest integer.

i = d. No explicit cast is necessary because any int can be stored in a double.

i = d. No explicit cast is necessary because d isn't changed in the conversion process.

Not all doubles can be stored as ints. You must sign off on the potential information loss with an explicit cast.

After the assignment s = ’slam’, which of the following code fragments prints scam?

s[1] = ’c’

print(s)

s.replace(’l’, ’c’)

print(s)

All of the above

None of the above

A doesn't work because Strings cannot be changed.  The [] operation can be used to read values inside a String, but not to change them.

B doesn't work because the replace() function does not change the String, it returns a new String.  This would work if it were s=s.replace('l', 'c').

C works, it's basically concatenating everything before the 'l' with a 'c' with everything after the 'l'.

In this question, you are given a Perl regular expression that you are required to evaluate.

There are no leading or trailing spaces in any of the text, nor are there any spaces in the regex.

Identify the answer which best matches the regex below:

/20[0-3]+/

205

0230

2300

20 followed by one or more digits in the range 0 to 3.

In this question, you are given a Perl regular expression that you are required to evaluate.

There are no leading or trailing spaces in any of the text, nor are there any spaces in the regex.

Identify the answer which matches the regex below:

/[A-Z][a-z]{2,4}day/

tuesday

Yesterday

Today

THURSDAY

Must start with an upper case letter, be followed by from 2 to 4 lower case letters, and be followed by day.

In this question, you are given a Perl regular expression that you are required to evaluate.

There are no leading or trailing spaces in any of the text, nor are there any spaces in the regex.

Identify the answer which matches the regex below:

/\d\d\d/

1d34

12

12A12D

Must contain 3 consecutive digits. It does not matter what comes before or after.

What are the merits of insertion sort compared to bubble sort and selection sort?

It doesn't require as much extra storage.

It copies elements only to their final locations.

It requires less code.

It can be implement recursively.

Neither selection nor bubble sort require extra storage. Selection sort doesn't make unnecessary copies. Bubble sort can be expressed in very little code. Any of them could be expressed recursively. If the array is already sorted, then insertion sort will only make N comparisons and no copies, giving it better performance than the other sorts.

What is the output of the following program?

public class Main {
  public static void swap(int a, int b) {
    int tmp = a;
    a = b;
    b = tmp;
  }

  public static void main(String[] args) {
    int a = 5, b = 7;
    swap(a, b);
    System.out.println(a + " " + b);
  }
}

7 5

5 5

7 7

12

Main.swap only receives copies of main's a and b. Its assignments do not alter main's variables. Thus, a is still 5 and b is still 7 when the print statement is executed.

In Java, what does it mean if something is marked static?

It never changes value.

It cannot be overridden.

Its value is undetermined.

It marks the program's starting point.

Something that is static is defined at the class level and is accessed through the class, rather than through an instance.

Suppose you've got a generic class:

class Rosters<T> {
  ...
}

You create a Rosters instance:

What is the erasure type of Rosters?

ArrayList<Object>

ArrayList<String>

Rosters

String

You need only examine the supertype of generic parameters on the Rosters class to determine the erasure type. There is no explicit supertype, so the supertype is Object.

Consider the following Python code:

in_str = input(’Enter a string: ’)
a = ’’
d = 0
r = 1

for c in ’abcdefghijklmnopqrstuvwxyz’:
    if c in in_str:
        a = c + a
    else:
        d = d + 1
r += 2

print(a) # Line 1
print(d) # Line 2
print(r) # Line 3

Given the input ’Frick & Frack’ what output is produced by Line 1?

FrickFrack

kcarkcir

acikr

none of the above

Essentially this is filtering out all the upper case and non-alphabetic characters.  The for loop goes through each lower-case letter, and if that letter is in the input string in_str, we concatenate the letter to the variable a.

Consider the following Python code:

in_str = input(’Enter a string: ’)
a = ’’
d = 0
r = 1

for c in ’abcdefghijklmnopqrstuvwxyz’:
   if c in in_str:
      a = c + a
   else:
      d = d + 1
r += 2

print(a) # Line 1
print(d) # Line 2
print(r) # Line 3

Given the input ’Frick & Frack’ what output is produced by Line 2?

5

10

86

none of the above

This basically counts the number of lower case letters.

What does the following Java code produce?

int result=1;
for (int i=1; i<=N; i++) {
   result *= 2;
}
System.out.println(result);

0

2*N

2^N+1

1

This produces 2^N. 

Which of the following expressions, when applied to each element of the array {0, 1, 2, 3, 4, 5, 6}, produces the array {0, 0, 1, 4, 5, 5, 9}?

x * 3 / 2 + x % 4

2 + x - x * x

x / 10 + x * 10 - x * x % 20

(10 - x) * -x

Your data has 4-bit keys. You also have magical, perfect hash function that will prevent any collisions from happening, provided there is room enough for all possible elements in the array. What's the minimum number of elements the array must be able to hold?

8

32

64

128

4-bit keys uniquely identify 2⁴ = 16 elements. The array must be able to hold these 16 items.

You've got this Word class for a project you are working on:

class Word {
  private String letters;
  ...
  public int hashCode() {
    return letters.charAt(1);
  }
}

For which of the word lists below is this implementation of hashCode a poor choice?

we, us, oh, by

aa, bb, cc, dd

mom, mill, mull, mat

dinosaur, paroxysm, levitate, apiary

The hashCode examines the second letter of each word to find the location in the hashtable. In list D, all words share the second letter 'a,' resulting in many collisions.

You know exactly how much data you need to store, but there's not much of it. You do not need to be able to search the collection quickly, but insertion should be as fast as possible. What is the simplest data structure that best suits for your needs?

Ordered array

Linked list

Hashtable

Binary search tree

If you know the memory needs, you can allocate a large enough array. Inserting elements in the array can be done in constant time, and requires less work than inserting in a linked list.

You've got this code:

TreeMap<String, String> map = new TreeMap<String, String>();
map.put("A", "*");
map.put("AA", "*");
map.put("B", "****");
for (String s : map.keySet()) {
  System.out.print(map.get(s) + " ");
}

What does it print?

A A B

A* AA* B****

A AA B

* ** ****

We iterate through each key {"A", "AA", "B"}, looking up and printing the value of these keys.

You see the expression n = null in code that successfully compiles. Which is not a legal type of n?

Integer

String

Object

ArrayList<String>

Boolean's can only be true or false.

The number of elements in a hashtable must be prime

so that linear probing will terminate

so that quadratic probing will terminate

to reduce collisions

to reduce cluster sizes

Since the double hash produces a fixed step size for probing, it may be the case that the step size is a factor of the table size. In this case, advancing by the fixed step size will land us in a cycling sequence.

You've got a class that holds two ints and that can be compared with other IntPair objects:

class IntPair {
  private int a;
  private int b;
  
  public IntPair(int a, int b) {
    this.a = a;
    this.b = b;
  }
 
  public int compareTo(IntPair other) {
    if (a < other.a) {
      return -1;
    } else if (a > other.a) {
      return 1;
    } else {
      if (b == other.b) {
        return 0;
      } else if (b > other.b) {
        return -1;
      } else {
        return 1;
      }
    }
  }
}

Let's denote new IntPair(5, 7) as [5 7]. You've got a list of IntPairs:

[3 7], [4 6], [3 4]

You sort them using IntPair.compareTo. What is their sorted order?

[3 4], [3 7], [4 6]

[4 6], [3 7], [3 4]

[4 6], [3 4], [3 7]

The compareTo orders first by IntPair.a in ascending order, and in the case of a tie, but IntPair.b in descending order.

What does the following Java code print?

int outer=0;
int inner=0;
for (int i=0; i<6; i++) {
   outer++;
   for (int j=0; j<=i; j++) {
      inner++;
   }
}
System.out.println("outer "+outer+", inner "+inner);

outer 6, inner i

outer 6, inner 24

outer 24, inner 24

outer 6, inner 24

The inner loop is based on the current iteration of the outer loop.  If we track the values:

outer 0, inner 0

outer 1, inner 0,1

outer 2, inner 0,1,2

and so on up to 6.

If we add up all of the inner values, there are 21 of them.

This is the classic "triangle" pattern, because the inner values proceed like this:

0

0 1

0 1 2

0 1 2 3

0 1 2 3 4

0 2 3 4 4 5

What does the following Java code print?

int outer=0;
for (int i=0; i<12; i++) {
   if (i % 2 == 0) {
      outer++;
   }
}
System.out.println(outer);

12

3

1

0

i % 2 == 0 is true only when i is 0.  This loop counts the number of even values between 0 and 12, exclusive (because the loop body doesn't execute when i is 12, the loop ends instead).  In this case the result is 6 (0, 2, 4, 6, 8, 10).

How many times does the following Java code print "hello world"?

for (int i=10; i>=4; i++) {
   System.out.print("hello world");
}

0

1

5

6

Trick question!  This is an infinite loop, because the update condition is i++, but we are starting at 10 and continue while i>=4!

What does the following Java code print?

for (int i=6; i>=2; i--) {
   System.out.print(i+" ");
}

6 5 4 3 2 1 0

6 5 4 3 2 1

6 5 4 3

the loop is infinite

This is a basic for loop that counts down from 6 to 2.

You are storing a complete binary tree in an array, with the root at index 0. At what index is node i's left child? 

2i

i + i + 2

i / 2 + 1

(i` - 1) / 2

Consider the following Python code:

in_str = input(’Enter a string: ’)
a = ’’
d = 0
r = 1

for c in ’abcdefghijklmnopqrstuvwxyz’:
   if c in in_str:
      a = c + a
   else:
      d = d + 1
r += 2

print(a) # Line 1
print(d) # Line 2
print(r) # Line 3

2

21

27

53

The statement r+=2 is not inside the loop, so we just assign 1 to r, then add 2 to it to get 3.

Consider the following Python code:

s = input(’Enter a string: ’)
w = ’’
for c in s:
   if c in "0123456789":
      #REPLACE
   else:
      w = w + c
print w

What replacement for the comment #REPLACE will cause the program to print the input string with all of the digits removed?  In other words, for the 'aaa3b3c1', we would print 'aaabc'.

break

return w

any of the above

none of the above

A is wrong because break will end the loop.

C is wrong because the problem asks us to print, not to return.

The continue statement works because it goes back to the top of the loop.

Consider the following Python code:

s = input(’Enter a string: ’)
w = ’’
for c in s:
   if c in "0123456789":
      #REPLACE
   else:
      w = w + c
print(w)

What replacement statement for the comment #REPLACE will cause the code to print out all of the characters up to the first digit?  In other words, if the input is 'aaa3bb3c1', we should output 'aaa'.

continue

return w

any of the above will work

none of the above

B is wrong because continue will skip the digits but continue with the rest of the String.

C is wrong because the exercise askes us to PRINT, not return the String.

Searching a heap is

O(1)

O(log N)

O(N log N)

O(N²)

In a heap, we only know that a node's key is greater than both its chidrens' keys. We may need to search both subheaps for an element. In the worst case, we'll visit every element.

What is the heap condition?

All but the leaf nodes have two children

The tree is a binary tree

Only the last level of the tree may not be full

No leaf node has children

All are true, but only C provides the definition of the heap condition.

Why can a heap be efficiently implemented using an array instead of a linked structure?

Linked implementations consume more space

The array never needs to change size

The heap condition makes it easier to calculate indices

We only traverse the heap in a breadth-first fashion

Because the heap is complete, the elements can be stored contiguously and parent and child nodes (which we're guaranteed to have) fall in locations we can compute with simple arithmetic.

You have a class Custom:

class Custom {
  private int i;
  ...
  public String toString() {
    return "" + i;
  }
}

Consider this code, which prints a Custom instance:

System.out.println(a);

What overloaded version of PrintStream.println is called?

println(String s)

println(Custom c)

println(int i)

println()

The version of println that we call must have a type that is a supertype of Custom, leaving only Custom and Object as our two choices. Since PrintStream was written years before our Custom class ever existed, it doesn't know anything about our class. However, it does know about Objects and that all Objects have a toString method.

What does the following Java code print?

int sum=0;
for (int i=1; i<=5; i++) {
   sum += i;
}
System.out.println(sum);

0

5

10

20

This is basically 1 + 2 + 3 + 4 + 5

What does the following Java code print?

int sum=0;
for (int i=0; i<10; i+=4) {
   sum += i;
}
System.out.println(sum);

4

8

16

20

0 + 4 + 8