____ 21. Constructors have the same name as the ____. a. member methods c. class
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Question
____ 21. Constructors have the same name as the ____.a. member methods c. class
b. data members d. package
____ 22. Which of the following is used to allocate memory for the instance variables of an object of a class?
a. the reserved word public c. the operator new
b. the reserved word static d. the operator +
____ 23. Consider the following statements.
public class Rectangle
{
private double length;
private double width;
public Rectangle()
{
length = 0;
width = 0;
}
public Rectangle(double l, double w)
{
length = l;
width = w;
}
public void set(double l, double w)
{
length = l;
width = w;
}
public void print()
{
System.out.println("Length = " + length
+ "; Width = " + width + " " +
+ " Area = " + area()
+ "; Perimeter = " + perimeter());
}
public double area()
{
return length * width;
}
public void perimeter()
{
return 2 * length + 2 * width;
}
}
Rectangle bigRect = new Rectangle (14, 10);
What is the output of the following statement?
bigRect.print();
a. Length = length; Width = width
Area = area; Perimeter = perimeter c. Length = 14.0; Width = 10.0
Area = 140.0; Perimeter = 48.0
b. Length = length Width = width
Area = area Perimeter = perimeter d. Length = 14.0 Width = 10.0
Area = 140.0 Perimeter = 48.0
____ 24. In ____ copying, each reference variable refers to its own object.
a. shallow c. method
b. deep d. object
public class Illustrate
{
private int x;
private static int y;
public static int count;
public static int z;
public Illustrate()
{
x = 1;
}
public Illustrate(int a)
{
x = a;
}
public void print()
{
System.out.println("x = " + x + ", y = "
+ y + ", count = " + count);
}
public static void incrementY()
{
y++;
}
}
____ 25. Which of the following statements would you use to declare a new reference variable of the type Illustrate and instantiate the object with a value of 9?
a. Illustrate illObject = new Illustrate(9);
b. illObject = Illustrate(9);
c. Illustrate illObject(9);
d. Illustrate.illObject(9);
____ 26. Which of the following declares an array of int named hits?
a. int hits; c. new int hits[];
b. int[] hits; d. int hits = int[];
int[] num = new int[100];
for (int i = 0; i < 50; i++)
num[i] = i;
num[5] = 10;
num[55] = 100;
____ 27. What is the data type of the array above?
a. int c. list
b. char d. num
____ 28. Consider the following declaration:
double[] sales = new double[50];
int j;
Which of the following correctly initializes all the components of the array sales to 10.
(i)
for (j = 0; j < 49; j++)
sales[j] = 10;
(ii)
for (j = 1; j <= 50; j++)
sales[j] = 10;
a. Only (i) c. Both (i) and (ii)
b. Only (ii) d. None of these
____ 29. What is the value of alpha[2] after the following code executes?
int[] alpha = new int[5];
int j;
for (j = 0; j < 5; j++)
alpha[j] = 2 * j + 1;
a. 1 c. 5
b. 4 d. 6
____ 30. What is stored in alpha after the following code executes?
int[] alpha = new int[5];
int j;
for (j = 0; j < 5; j++)
{
alpha[j] = j + 1;
if (j > 2)
alpha[j - 1] = alpha[j] + 2;
}
a. alpha = {1, 5, 6, 7, 5} c. alpha = {4, 5, 6, 7, 9}
b. alpha = {1, 2, 3, 4, 5} d. None of these
____ 31. What is the output of the following Java code?
int[] alpha = {2, 4, 6, 8, 10};
int j;
for (j = 4; j >= 0; j--)
System.out.print(alpha[j] + " ");
System.out.println();
a. 2 4 6 8 10 c. 4 3 2 1 0
b. 10 8 6 4 2 d. Invalid code
int[] array1 = {1, 3, 5, 7}
for (int i = 0; i <array.length; i++)
if (array1[i] > 5)
System.out.println(i + " " + array1[i]);
____ 32. What is the output of the code fragment above?
a. 0 3 c. 7 3
b. 3 7 d. 5 1
int[] x = new int[10];
x[0] = 34;
x[1] = 88;
System.out.println(x[0] + " " + x[1] + " " + x[10]);
____ 33. What is the output of the code fragment above?
a. 34 88 0
b. 34 88 88
c. 0 34 88
d. This program throws an exception.
____ 34. Suppose that sales is a two dimensional array of 10 rows and 7 columns wherein each component is of the type int , and sum and j are int variables. Which of the following correctly finds the sum of the elements of the fifth row of sales?
a. sum = 0;
for(j = 0; j < 7; j++)
sum = sum + sales[5][j]; c. sum = 0;
for(j = 0; j < 10; j++)
sum = sum + sales[5][j];
b. sum = 0;
for(j = 0; j < 7; j++)
sum = sum + sales[4][j]; d. sum = 0;
for(j = 0; j < 10; j++)
sum = sum + sales[4][j];
____ 35. A subclass can directly access ____.
a. public members of a superclass c. all members of a superclass
b. private members of a superclass d. none of the members of a superclass
____ 36. Consider the following class definitions.
public class BClass
{
private int x;
private double y;
public void print() { }
}
public class DClass extends BClass
{
private int a;
private int b;
public void print() { }
}
Suppose that you have the following statement.
DClass dObject = new DClass();
How many instance variables DObject has?
a. 0 c. 4
b. 2 d. None of these
____ 37. Consider the following class definitions.
public class BClass
{
private int x;
public void set(int a) { x = a; }
public void print(){ }
}
public class DClass extends BClass
{
private int y;
public void set(int a, int b)
{
//Postcondition: x = a; y = b;
}
public void print(){ }
}
Which of the following is the correct definition of the method set of the class Dclass?
(i)
public void set(int a, int b)
{
super.set(a);
y = b;
}
(ii)
public void set(int a, int b)
{
x = a;
y = b;
}
a. Only (i) c. Both (i) and (ii)
b. Only (ii) d. None of these
____ 38. Based on the diagrams above, which of the following is the superclass?
a. Rectangle c. area()
b. Box d. volume()
____ 39. Suppose that the class Mystery is derived from the class Secret. Consider the following statements:
Secret mySecret = new Secret();
Secret secRef;
Mystery myMystery = new Mystery();
Mystery mysRef;
secRef = myMystery;
Which of the following statements is legal in Java?
(i) mysRef = (Mystery) mySecret;
(ii) mysRef = (Mystery) secRef;
a. Only (i) c. Both (i) and (ii)
b. Only (ii) d. None of these
____ 40. Which operator is used to determine if an object is of a particular class type?
a. The operator new c. The instanceof operator
b. The dot (.) operator d. The + operator
Explanation / Answer
21. Constructors have the same name as the ____.
c. class
22. Which of the following is used to allocate memory for the instance variables of an object of a class?
c. the operator new
23. Output of the code..
c or d.
Length = 14.0 Width = 10.0
Area = 140.0 Perimeter = 48.0
24. In ____ copying, each reference variable refers to its own object.
b. deep
25. Which of the following statements would you use to declare a new reference variable of the type Illustrate and instantiate the object with a value of 9?
a. Illustrate illObject = new Illustrate(9);
26. Which of the following declares an array of int named hits?
b. int[] hits;
27. What is the data type of the array above?
a. int
28. Consider the following declaration:
d. None of these
29. What is the value of alpha[2] after the following code executes?
c. 5
30. What is stored in alpha after the following code executes?
d. None of these
31. What is the output of the following Java code?
b. 10 8 6 4 2
32. What is the output of the code fragment above?
b. 3 7
33. What is the output of the code fragment above?
a. 34 88 0
34. Suppose that sales is a two dimensional array of 10 rows and 7 columns wherein each component is of the type int , and sum and j are int variables. Which of the following correctly finds the sum of the elements of the fifth row of sales?
b. sum = 0;
for(j = 0; j < 7; j++)
sum = sum + sales[4][j];
35. A subclass can directly access ____.
a. public members of a superclass
36. Consider the following class definitions.
a. 0
37. Consider the following class definitions.
a. Only (i)
38. Based on the diagrams above, which of the following is the superclass?
b. Box (here diagram is not given so its a guess..)
39. Suppose that the class Mystery is derived from the class Secret. Consider the following statements:
c. Both (i) and (ii)
40. Which operator is used to determine if an object is of a particular class type?
c. The instanceof operator
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