Question 1

What is the printout for the following code? class Test {
Public static void main(String[] args) {
Int[] x = new int[3];
System.out.println("x[0] is "+x[0]);
}
}

Accepted Answer

A)   The program has a syntax error because the size of the array wasn't specified when declaring the array.
B)   The program has a runtime error because the array elements are not initialized.
C)   The program runs fine and displays x[0] is 0.
D)   None of the above. C

Question 2

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);

Accepted Answer

A)   'a'
B)   'v'
C)   Nothing will be assigned to x, because the execution causes the runtime error StringIndexOutofBoundsException.
D)   None of the above. C

Question 3

To append data to an existing file, use _____________ to construct a FileOutputStream for file out.dat.

Accepted Answer

A)   new FileOutputStream("out.dat") 
B)   new FileOutputStream("out.dat", false) 
C)   new FileOutputStream("out.dat", true) 
D)   new FileOutputStream(true, "out.dat")  C

Question 4

Suppose the xMethod() is invoked in the following constructor in a class, xMethod() is _________ in the class. public MyClass() {
XMethod();
}

Accepted Answer

A)   a static method
B)   an instance method
C)   a static method or an instance method

Question 5

Analyze the following code: public class Test {
Private int t;
Public static void main(String[] args) {
Test test = new Test();
System.out.println(test.t);
}
}

Accepted Answer

A)   The variable t is not initialized and therefore causes errors.
B)   The variable t is private and therefore cannot be accessed in the main method.
C)   Since t is an instance variable, it cannot appear in the static main method.
D)   The program compiles and runs fine.

Question 6

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();
}
}
a. none
b. "The default constructor of B is invoked"
c. "The default constructor of A is invoked" followed by "The default constructor of B is invoked"
d. "The default constructor of A is invoked"

Accepted Answer

The answer of What is the output of running class...

Question 7

Which code fragment would correctly identify the number of arguments passed via the command line to a Java application, excluding the name of the class that is being invoked?

Accepted Answer

A)   int count = args.length;
B)   int count = args.length - 1;
C)   int count = 0; while (args[count] != null)  count ++;
D)   int count=0; while (!(args[count].equals("") ) )  count ++;

Question 8

What modifier should you use on a variable so that it can only be referenced inside its defining class.

Accepted Answer

A)   public
B)   private
C)   protected
D)   Use the default modifier.

Question 9

_________ describes the state of an object.

Accepted Answer

A)   data fields
B)   methods
C)   constructors
D)   none of the above

Question 10

What would be the result of attempting to compile and run the following code? public class Test {
Static int x;
Public static void main(String[] args){
System.out.println("Value is " + x);
}
}

Accepted Answer

A)   The output "Value is 0" is printed.
B)   An "illegal array declaration syntax" compiler error occurs.
C)   A "possible reference before assignment" compiler error occurs.
D)   A runtime error occurs, because x is not initialized.

Question 11

When you implement a method that is defined in a superclass, you __________ the original method.

Accepted Answer

A)   overload
B)   override
C)   copy
D)   call

Question 12

Text I/O 
Write a program that will count the number of characters (excluding control characters '' and '
'), words, and lines, in a file. Words are separated by spaces, tabs, carriage return, or line-feed characters. The file name should be passed as a command-line argument, as shown in the following sample run.

Accepted Answer

The answer of Text I/O 
Write a program that will...

Question 13

Suppose the xMethod() is invoked from a main method in a class as follows, xMethod() is _________ in the class. public static void main(String[] args) {
XMethod();
}

Accepted Answer

A)   a static method
B)   an instance method
C)   a static or an instance method

Question 14

Show the output of running the class Test in the following code lines: interface A {
Void print();
}
Class C {}
Class B extends C implements A {
Public void print() { }
}
Class Test {
Public static void main(String[] args) {
B b = new B();
If (b instanceof A)
System.out.println("b is an instance of A");
If (b instanceof C)
System.out.println("b is an instance of C");
}
}

Accepted Answer

A)   Nothing.
B)   b is an instance of A.
C)   b is an instance of C.
D)   b is an instance of A followed by b is an instance of C.

Question 15

Design and use interfaces 
Write a class named Octagon that extends GeometricObject and implements the Comparable and Cloneable interfaces. Assume that all eight sides of the octagon are of equal size. The area can be computed using the following formula:  Draw the UML diagram that involves Octagon, GeometricObject, Comparable, and Cloneable.

Accepted Answer

The answer of Design and use interfaces 
Write a class...

Question 16

After the following program is finished, how many bytes are written to the file t.dat? import java.io.*;
Public class Test {
Public static void main(String[] args) throws IOException {
DataOutputStream output = new DataOutputStream(
New FileOutputStream("t.dat"));
Output.writeShort(1234);
Output.writeShort(5678);
Output.close();
}
}

Accepted Answer

A)   2 bytes.
B)   4 bytes.
C)   8 bytes.
D)   16 bytes.

Question 17

Design and create GUI applications 
Write a Java applet to add two numbers from text fields, and displays the result in a non-editable text field. Enable your applet to run standalone with a main method. A sample run of the applet is shown in the following figure.

Accepted Answer

The answer of Design and create GUI applications 
Write a...

Question 18

If a class named Student has no constructors defined explicitly, the following constructor is implicitly provided.

Accepted Answer

A)   public Student() 
B)   protected Student() 
C)   private Student() 
D)   Student()

Question 19

How can you get the word "abc" in the main method from the following call? java Test "+" 3 "abc" 2

Accepted Answer

A)   args[0]
B)   args[1]
C)   args[2]
D)   args[3]

Question 20

If a class named Student has a constructor Student(String name) defined explicitly, the following constructor is implicitly provided.

Accepted Answer

A)   public Student() 
B)   protected Student() 
C)   private Student() 
D)   Student() 
E)   None

Exam 10: Thinking in Objects

What is the printout for the following code? class Test { Public static void main(String[] args) { Int[] x = new int[3]; System.out.println("x[0] is "+x[0]) ; } }

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) ;

To append data to an existing file, use _____________ to construct a FileOutputStream for file out.dat.

Suppose the xMethod() is invoked in the following constructor in a class, xMethod() is _________ in the class. public MyClass() { XMethod() ; }

Analyze the following code: public class Test { Private int t; Public static void main(String[] args) { Test test = new Test() ; System.out.println(test.t) ; } }