Finals Study Guide (Multiple Choice Section) Flashcards
Which of the following statements is correct to display Welcome to Java on the console? (Choose all that apply.)
System.out.println(“Welcome to Java”);
System.out.print(“Welcome to Java”);
________ is the brain of a computer.
CPU
Every letter in a Java keyword is in lowercase.
false
To declare a constant MAX_LENGTH inside a method with value 99.98, you write
final double MAX_LENGTH = 99.98;
________ is the physical aspect of the computer that can be seen.
Hardware
________is interpreted.
Java
Which of the following assignment statements is incorrect? (Choose all that apply.)
i = 1 = j = 1 = k = 1;
i = 1; j = 1; k = 1;
i == j == k == 1;
A block is enclosed inside ________.
braces
The main method header is written as:
public static void main(String[ ] args)
If you enter 1 2 3, when you run this program, what will be the output?
import java.util.Scanner;
public class Test1 {
public static void main(String[ ] args) {
Scanner input = new Scanner(System.in);
System.out.print("Enter three numbers: ");
double number1 = input.nextDouble();
double number2 = input.nextDouble();
double number3 = input.nextDouble();
// Compute average
double average = (number1 + number2 + number3) / 3;
// Display result
System.out.println(average);
}
}
2.0
________ is the Java assignment operator.
=
________ are instructions to the computer. (Choose two.)
Programs
Software
Which of the following are correct ways to declare variables? (Choose two.)
int length, width;
int length; int width;
Which of the following is a valid identifier? (Choose all that apply.)
class
$343
radius
Suppose you define a Java class as follows:
public class Test {
}
In order to compile this program, the source code should be stored in a file named
Test.java
One byte has ________ bits.
8
To assign a value 1 to variable x, you write
x = 1;
Every statement in Java ends with ________.
a semicolon (;)
Which of the following are correct names for variables according to Java naming conventions? (Choose all that apply.)
radius
findArea
Suppose a Scanner object is created as follows:
Scanner input = new Scanner(System.in);
What method do you use to read an int value?
input.nextInt();
What is 1 + 1 + 1 + 1 + 1 == 5?
true
What is the printout of the following switch statement?
char ch = 'a';
switch (ch) {
case 'a':
case 'A':
System.out.print(ch); break;
case 'b':
case 'B':
System.out.print(ch); break;
case 'c':
case 'C':
System.out.print(ch); break;
case 'd':
case 'D':
System.out.print(ch);
}a
What is the printout of the following switch statement?
char ch = ‘b’;
switch (ch) {
case 'a':
System.out.print(ch);
case 'b':
System.out.print(ch);
case 'c':
System.out.print(ch);
case 'd':
System.out.print(ch);
}
bbb
Analyze the following code:
if (x < 100) && (x > 10)
System.out.println(“x is between 10 and 100”);
The statement has compile errors because (x 10) must be enclosed inside parentheses.
The equal comparison operator in Java is ________.
==
Suppose income is 4001, what is the output of the following code:
if (income > 3000) {
System.out.println("Income is greater than 3000");
}
else if (income > 4000) {
System.out.println("Income is greater than 4000");
}
Income is greater than 3000
Analyze the following code.
boolean even = false;
if (even) {
System.out.println(“It is even!”);
}
The code displays nothing.
Which of the following code displays the area of a circle if the radius is strictly positive?
if (radius > 0) System.out.println(radius * radius * 3.14159);
Which of the following is the correct expression that evaluates to true if the number x is between 1 and 100 or the number is negative?
((x < 100) && (x > 1)) || (x < 0)
In Java, the word true is ________.
a Boolean literal
The following code displays ________.
double temperature = 50;
if (temperature >= 100)
System.out.println("too hot");
else if (temperature );
just right
Suppose x = 1, y = -1, and z = 1. What is the printout of the following statement?
if (x > 0)
if (y > 0)
System.out.println("x > 0 and y > 0");
else if (z > 0)
System.out.println("x 0");
x 0;
Which of the Boolean expressions below is incorrect? (Choose three.)
(x != 0) || (x = 0)
(true) && (3 => 4)
(-10 < x < 0)
How many times will the following code print “Welcome to Java”?
int count = 0;
while (count < 10) {
System.out.println("Welcome to Java");
count++;
}
10
Do the following two statements in (I) and (II) result in the same value in sum?
(I):
for (int i = 0; i<10; i++) {
sum += i;
}
Yes
How many times will the following code print “Welcome to Java”?
int count = 0;
do {
System.out.println("Welcome to Java");
count++;
} while (count < 10);
10
What is the output for y?
int sum = 0;
for (int i = 0; i<10; ++i) {
sum += i;
}
System.out.println(sum);
45
(char)(‘a’ + Math.random() * (‘z’ - ‘a’ + 1)) returns a random character ________.
between ‘a’ and ‘z’
A variable defined inside a method is referred to as ________.
a local variable
All Java applications must have a method ________.
public static void main(String[ ] args)
Analyze the following code:
class Test {
public static void main(String[ ] args) {
System.out.println(xmethod(5));
}
public static int xmethod(int n, long t) {
System.out.println("int");
return n;
}
public static long xmethod(long n) {
System.out.println("long");
return n;
}
}
The program displays long followed by 5.
Analyze the following code:
public class Test {
public static void main(String[ ] args) {
System.out.println(xMethod(5, 500L));
}
public static int xMethod(int n, long l) {
System.out.println("int, long");
return n;
}
public static long xMethod(long n, long l) {
System.out.println("long, long");
return n;
} }
The program displays int, long followed by 5.
Arguments to methods always appear within ________.
parentheses
Does the method call in the following method cause compile errors?
public static void main(String[ ] args) {
Math.pow(2, 4);
}
No
Does the return statement in the following method cause compile errors?
public static void main(String[ ] args) {
int max = 0;
if (max != 0)
System.out.println(max);
else
return;
}
No
Each time a method is invoked, the system stores parameters and local variables in an area of memory, known as ________, which stores elements in last-in first-out fashion.
a stack
Given the following method
static void nPrint(String message, int n) {
while (n > 0) {
System.out.print(message);
n--;
}
}
What is the printout of the call nPrint(‘a’, 4)?
invalid call
Given the following method
static void nPrint(String message, int n) {
while (n > 0) {
System.out.print(message);
n--;
}
}
What is k after invoking nPrint(“A message”, k)?
int k = 2;
nPrint(“A message”, k);
2
Suppose your method does not return any value, which of the following keywords can be used as a return type?
void
The client can use a method without knowing how it is implemented. The details of the implementation are encapsulated in the method and hidden from the client who invokes the method. This is known as ________. (Choose all that apply.)
information hiding
The signature of a method consists of ________.
method name and parameter list
What is k after the following block executes?
{
int k = 2;
nPrint("A message", k);
}
System.out.println(k);
k is not defined outside the block. So, the program has a compile error
When you invoke a method with a parameter, the value of the argument is passed to the parameter. This is referred to as ________.
pass by value
Which of the following is a possible output from invoking Math.random()? (Choose all that apply.)
- 5
0. 0
Which of the following should be declared as a void method?
Write a method that prints integers from 1 to 100.
A method that is associated with an individual object is called ________.
a class instance
An object is an instance of a ________.
class
Analyze the following code.
class Test {
public static void main(String[ ] args) {
String s;
System.out.println("s is " + s);
}
}
The program has a compilation error because s is not initialized, but it is referenced in the println statement.
Analyze the following code.
public class Test {
int x;
public Test(String t) {
System.out.println("Test");
}
public static void main(String[ ] args) {
Test test = new Test();
System.out.println(test.x);
}
}
The program has a compile error because Test does not have a default constructor.
Given the declaration Circle x = new Circle(), which of the following statement is most accurate?
x contains a reference to a Circle object.
Given the declaration Circle[ ] x = new Circle[10], which of the following statement is most accurate?
x contains a reference to an array and each element in the array can hold a reference to a Circle object.
Suppose s is a string with the value “java”. What will be assigned to x if you execute the following code?
char x = s.charAt(4);
Nothing will be assigned to x, because the execution causes the runtime error StringIndexOutofBoundsException.
The keyword ________ is required to declare a class.
class
What is displayed by the following code?
public static void main(String[ ] args) throws Exception {
String[ ] tokens = “Welcome to Java”.split(“o”);
for (int i = 0; i
Welc me t Java
What is the output of the following code?
String s = “University”;
s.replace(“i”, “ABC”);
System.out.println(s);
University
What is the output of the following code?
public class Test {
public static void main(String[ ] args) {
String s1 = "Welcome to Java!";
String s2 = "Welcome to Java!";
if (s1 == s2)
System.out.println("s1 and s2 reference to the same String object");
else
System.out.println("s1 and s2 reference to different String objects");
} }
s1 and s2 reference to the same String object
What is the output of the following code?
public class Test {
public static void main(String[ ] args) {
String s1 = new String("Welcome to Java!");
String s2 = new String("Welcome to Java!");
if (s1 == s2)
System.out.println("s1 and s2 reference to the same String object");
else
System.out.println("s1 and s2 reference to different String objects");
} }
s1 and s2 reference to different String objects
What is the output of the following code?
public class Test {
public static void main(String[ ] args) {
String s1 = new String("Welcome to Java!");
String s2 = new String("Welcome to Java!");
if (s1.equals(s2))
System.out.println("s1 and s2 have the same contents");
else
System.out.println("s1 and s2 have different contents");
} }
s1 and s2 have the same contents
What is wrong in the following code?
class TempClass {
int i;
public void TempClass(int j) {
int i = j;
}
}
public class C {
public static void main(String[ ] args) {
TempClass temp = new TempClass(2);
}
}
The program has a compilation error because TempClass does not have a constructor with an int argument.
When invoking a method with an object argument, ________ is passed.
the reference of the object
Which of the following statements is most accurate? (Choose two.)
A reference variable refers to an object.
An object may contain the references of other objects.
Which of the following statements is preferred to create a string “Welcome to Java”?
String s = “Welcome to Java”;
________ is a construct that defines objects of the same type.
A class
________ is invoked to create an object.
A constructor
________ represents an entity in the real world that can be distinctly identified.
An object
You can declare two variables with the same name in ________.
different methods in a class
Object-oriented programming allows you to derive new classes from existing classes. This is called ________.
inheritance
Which of the following statements are true? (Choose two.)
A subclass is usually extended to contain more functions and more detailed information than its superclass.
“class A extends B” means A is a subclass of B.
Suppose you create a class Cylinder to be a subclass of Circle. Analyze the following code:
class Cylinder extends Circle {
double length;
Cylinder(double radius) {
Circle(radius);
} }
The program has a compile error because you attempted to invoke the Circle class’s constructor illegally.
What is the output of running class C?
class A {
public A() {
System.out.println("The default constructor of A is invoked");
}
}
class B extends A {
public B() {
System.out.println("The default constructor of B is invoked");
}
}
public class C {
public static void main(String[ ] args) {
B b = new B();
}
}
“The default constructor of A is invoked”“The default constructor of B is invoked”
Analyze the following code:
public class Test {
public static void main(String[ ] args) {
B b = new B();
b.m(5);
System.out.println("i is " + b.i);
}
}
class A {
int i;
public void m(int i) {
this.i = i;
} }
class B extends A {
public void m(String s) {
}
}
The method m is not overridden in B. B inherits the method m from A and defines an overloaded method m in B.
Given the following code, find the compile error. (Choose two.)
public class Test {
public static void main(String[ ] args) {
m(new GraduateStudent());
m(new Student());
m(new Person());
m(new Object());
}
public static void m(Student x) {
System.out.println(x.toString());
} }
class GraduateStudent extends Student {
}
class Student extends Person {
public String toString() {
return "Student";
}
}
class Person extends Object {
public String toString() {
return "Person";
}
}
m(new Person()) causes an error
m(new Object()) causes an error
Analyze the following code: (Choose two.)
public class Test {
public static void main(String[ ] args) {
Object a1 = new A();
Object a2 = new Object();
System.out.println(a1);
System.out.println(a2);
}
}
class A {
int x;
public String toString() {
return "A's x is " + x;
}
}
When executing System.out.println(a2), the toString() method in the Object class is invoked.
When executing System.out.println(a1), the toString() method in the A class is invoked.
