AP Computer Science Java Practice Exam #2

What is the output of the following program segment?

int num = 5;

while (num >= 0)

{

num -= 2;

}

System.out.println(num);

• -2

• -1

• 0

• 2

• 21

What is the output from

int n = 12;

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

System.out.print(" " + n);

where the method goFigure is defined as follows:

public double goFigure(int n)

{

n %= 7;

return (double) (12 / n);

}

• 2.0 12

• 2.4 12

• 2.0 5

• 2.4 5

• 2.4 6

Which of the following expressions will evaluate to true when x and y are boolean variables with different values?

I. (x || y) && (!x || !y)

II. (x || y) && !(x && y)

III. (x && !y) || (!x && y)

• I only

• II only

• I and II only

• II and III only

• I, II, and III

What is the output from the following code segment?

double x = 5*4/2 - 5/2*4;

System.out.println(x);

• 0

• 1

• 0.0

• 1.0

• 2.0

What is the output from the following code segment?

String band = "anamanaguchi";

System.out.println(band.substring(1, 4)). compareTo(band.substring(5, 8)));

• true

• false

• 0

• A negative integer

• A positive integer

Integers can be represented in number systems with different bases. Fr example, 34(decimal) = 22(hexadecimal) = 100010(binary), where the subscripts "dec", "hex", and "bin" indicate the decimal (base 10), hexadecimal (base 16), and binary (base 2) systems, respectively. What are the hexadecimal and binary representations of 49(decimal)?

• 49(decimal) = 21(hexadecimal) = 110011(binary)

• 49(decimal) = 31(hexadecimal) = 11001(binary)

• 49(decimal) = 31(hexadecimal) = 110001(binary)

• 49(decimal) = 37(hexadecimal) = 110111(binary)

• 49(decimal) = 61(hexadecimal) = 110001(binary)

Questions 7-8 refer to the following method

public void printVals(String[] items, int k)

{

if(k > 1)

{

printVals(items, k - 1);

System.out.print(items[k] + " ");

printVals(items, k - 2);

}

}

Suppose the following code segment has been executed.

String[] names = {"Pat", "Joe", "Ann", "Cal", "Amy"};

printVals(names, name.length - 1);

7.What is the output?

• Ann Cal Amy Ann

• Ann Cal Amy Cal Ann

• Ann Cal Joe Amy Joe Ann

• Joe Ann Cal Joe Amy Joe Ann

• Joe Ann Pat Cal Joe Amy Joe Ann Pat

public void printVals(String[] items, int k)

{

if(k > 1)

{

printVals(items, k - 1);

System.out.print(items[k] + " ");

printVals(items, k - 2);

}

}

Suppose the following code segment has been executed.

String[] names = {"Pat", "Joe", "Ann", "Cal", "Amy"};

printVals(names, name.length - 1);

How many calls to printVals have have been made, including the original call?

• 3

• 5

• 7

• 8

• 9

Consider the following code segment.

String abc = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

< missing statement >

System.out.println(abc.substring(k, k + 1));

It is supposed to print a randomly chosen letter of the alphabet. Any of the 26 letters can be chosen with equal probability. Which of the following can replace <missing statement> for the code to work that way?

• int k = Math.random(25);

• int k = Math.random(0, 25);

• int k = Math.random(25) + 1;

• int k = Math.random(26) - 1;

• int = k = (int)(26*Math.random());

In OOP, programmers often arrange classes into inheritance hierarchies instead of implementing isolated classes. Which of the following is NOT a valid reason for doing so?

• Abstract classes at the top of the hierarchy can be extended in the project or reused in other projects.

• Methods from a superclass can often be reused in its subclasses without duplication of code.

• Objects from different subclasses can be passed as parameters to a method designed to accept objects of the superclass.

• Objects from different subclasses can be stored in the same array.

• All of the above are valid reasons for using inheritance hierarchies.