Unit 7

Question 1

What is the primary goal of defensive programming?

A) To ensure the program only runs in secure environments
B) To make the software robust, reusable, maintainable, and understandable
C) To maximize software performance
D) To minimize the number of features in the software

Answer 1

B) To make the software robust, reusable, maintainable, and understandable

Question 2

Which tool or technique is commonly used in defensive programming to handle unexpected problems?

A) Code obfuscation
B) Using exceptions
C) Decreasing code readability
D) Avoiding user input

Answer 2

B) Using exceptions

Question 3

What should a program do when an error occurs at runtime, according to defensive programming principles?

A) Stop immediately to prevent damage
B) Detect, report, and deal with the problem appropriately
C) Ignore minor errors
D) Reboot the system

Answer 3

B) Detect, report, and deal with the problem appropriately

Question 4

What is the issue with adding validation code for every method, according to best practices in defensive programming?

A) It makes the code too robust
B) It can make the code unnecessarily long and hard to read
C) It improves the performance of the program
D) It simplifies the code

Answer 4

B) It can make the code unnecessarily long and hard to read

Question 5

What is the Java solution for handling exceptions that disrupt the normal flow of instructions?

A) To use conditional statements
B) To handle exceptions using a specific mechanism for passing control
C) To rewrite the program without exceptions
D) To ignore the exceptions

Answer 5

B) To handle exceptions using a specific mechanism for passing control

Question 6

What does Java do when a runtime exception occurs?

A) It pauses the execution until the error is fixed
B) The Java Virtual Machine throws an exception
C) It sends an email to the developer
D) It automatically fixes the error

Answer 6

B) The Java Virtual Machine throws an exception

Question 7

How are exceptions categorized in Java?

A) Checked and unchecked exceptions
B) Minor and major exceptions
C) Internal and external exceptions
D) Permanent and temporary exceptions

Answer 7

A) Checked and unchecked exceptions

Question 8

What is true about unchecked exceptions in Java?

A) They must be declared in a method’s throws clause
B) They are under programmer’s control
C) They occur due to programming errors
D) They cannot be handled or caught

Answer 8

C) They occur due to programming errors

Question 9

What will be the output if the following code encounters an ArrayIndexOutOfBoundsException?
try {
int[] arr = {1, 2, 3};
System.out.println(arr[3]);
} catch (ArrayIndexOutOfBoundsException e) {
System.out.println(“Error: “ + e.getMessage());
}
A) The program will crash
B) “Error: Index 3 out of bounds for length 3”
C) No output
D) It will print “3”

Answer 9

B) “Error: Index 3 out of bounds for length 3”

Question 10

What is a finally block used for in Java?

A) To execute code after a try-catch block, regardless of whether an exception was thrown
B) To execute code only if an exception occurs
C) To handle all types of exceptions
D) To finally end the execution of the program

Answer 10

A) To execute code after a try-catch block, regardless of whether an exception was thrown

Question 11

What is serialization in Java?

A) Converting a byte stream to characters
B) Converting an object into a sequence of bytes
C) Increasing the efficiency of file I/O
D) Encrypting files

Answer 11

B) Converting an object into a sequence of bytes

Question 12

What must a class implement to be serializable?

A) Serializable interface
B) Externalizable interface
C) Cloneable interface
D) Streamable interface

Answer 12

A) Serializable interface

Question 13

What is the purpose of the FileOutputStream class in Java?

A) To read data from files
B) To serialize objects
C) To write data to files
D) To monitor file changes

Answer 13

C) To write data to files

Question 14

What happens when you serialize an object with a transient attribute?

A) The attribute is serialized normally
B) The attribute is not serialized
C) The attribute is encrypted
D) Serialization fails

Answer 14

B) The attribute is not serialized

Question 15

How do you handle a FileNotFoundException in Java?

A) By declaring it in the throws clause of the method
B) By using a finally block
C) By ignoring it
D) By using a for loop

Answer 15

A) By declaring it in the throws clause of the method

Question 16

What is the result of executing the following code if the file does not exist?

try {
FileInputStream fis = new FileInputStream(“nonexistent.txt”);
} catch (FileNotFoundException e) {
System.out.println(“File not found.”);
}
A) Compilation error
B) “File not found.”
C) The program crashes
D) Nothing happens

Answer 16

B) “File not found.”

Question 17

What is the correct way to append text to an existing file using FileOutputStream?

A) new FileOutputStream(“file.txt”, true)
B) new FileOutputStream(“file.txt”, false)
C) new FileOutputStream(“file.txt”)
D) new File(“file.txt”).append()

Answer 17

A) new FileOutputStream(“file.txt”, true)

Question 18

Which method from the Scanner class is used to read an entire line from a file?

A) readLine()
B) nextLine()
C) getLine()
D) read()

Answer 18

B) nextLine()

Question 19

What is the primary difference between checked and unchecked exceptions?

A) Checked exceptions are for file operations, unchecked are for memory errors
B) Checked exceptions are for errors you can anticipate, unchecked are for programming errors
C) Checked exceptions are recoverable, unchecked are not
D) There is no difference; it’s just naming

Answer 19

B) Checked exceptions are for errors you can anticipate, unchecked are for programming errors

Question 20

Which statement is true about PrintStream?

A) It is used to read from files
B) It can only print text to the console
C) It is used to write formatted representations of objects to text-output streams
D) It is not part of the Java I/O package

Answer 20

C) It is used to write formatted representations of objects to text-output streams

Question 21

What does PrintStream do when you pass null to one of its print methods?
A) Throws a NullPointerException.
B) Prints the string “null”.
C) Causes a compile-time error.
D) Does nothing.

Answer 21

B) Prints the string “null”

Question 22

Which exception is thrown when trying to access an index that is out of bounds for an array?
A) ArrayIndexOutOfBoundsException
B) OutOfBoundsException
C) IndexOutOfBoundsException
D) ArrayBoundsException

Answer 22

A) ArrayIndexOutOfBoundsException

Question 23

What will be the result of trying to deserialize an object whose serializable class has changed since it was serialized?
A) InvalidClassException
B) IOException
C) ClassNotFoundException
D) The object will be deserialized without any issues.

Answer 23

A) InvalidClassException

Question 24

How do you ensure that a resource is closed even if an exception occurs in Java?
A) By closing the resource at the beginning of a try block.
B) By closing the resource in a catch block.
C) By closing the resource in a finally block.
D) By relying on garbage collection.

Answer 24

C) By closing the resource in a finally block

Question 25

What is the primary use of the throw keyword in Java? A) To handle an exception. B) To define a new exception. C) To declare an exception. D) To manually trigger an exception.

Answer 25

C) To declare an exception.

Question 26

When a method is declared with a throws clause, what does it mean? A) The method handles the specified exceptions. B) The method guarantees that it will not cause any exceptions. C) The method may pass the specified exceptions to its caller. D) The method suppresses all exceptions.

Answer 26

C) The method may pass the specified exceptions to its caller

Question 27

What is the advantage of custom exceptions in Java? A) They allow methods to throw any type of runtime error. B) They provide a means to differentiate an error condition and handle it accordingly. C) They eliminate the need for try-catch blocks. D) They improve the performance of the application.

Answer 27

B) They provide a means to differentiate an error condition and handle it accordingly

Question 28

Which of the following is not a correct statement about the finally block? A) It is executed after the try block, regardless of whether an exception was thrown or not. B) It must always accompany a try block. C) It is used to execute important code such as closing resource connections. D) It can be used without a catch block.

Answer 28

B) It must always accompany a try block (Note: It doesn't have to always accompany a try block; it can stand with just a try without catch.)

Question 29

What will happen if a finally block throws an exception? A) The exception from the finally block is suppressed. B) Any exception thrown in the try block is ignored. C) The exception from the finally block is thrown to the next higher context. D) The program will immediately terminate.

Answer 29

C) The exception from the finally block is thrown to the next higher context

Question 30

Which of the following best describes the concept of exception chaining in Java? A) Preventing an exception from propagating. B) Catching one exception and throwing a new exception that includes it. C) Linking multiple catch blocks together. D) Creating a list of possible exceptions to catch.

Answer 30

B) Catching one exception and throwing a new exception that includes it

Question 31

What is the purpose of using the transient keyword in Java serialization? A) To indicate that the variable should be serialized. B) To ensure the variable is encrypted during serialization. C) To prevent the variable from being serialized. D) To mark the variable as volatile.

Answer 31

C) To prevent the variable from being serialized

Question 32

What is the correct way to use try-with-resources in Java? A) try (Resource r = new Resource()) { /* use r */ } B) try { Resource r = new Resource(); /* use r */ } C) try (Resource r) { /* use r */ } D) try { Resource r = new Resource(); /* use r */ } finally { r.close(); }

Answer 32

A) try (Resource r = new Resource()) { /* use r */ }

Question 33

Why would a developer define a custom exception in Java? A) To handle all types of runtime exceptions. B) To provide clearer, more specific error handling tailored to their application. C) To increase the execution speed of the application. D) To comply with Java standard library requirements.

Answer 33

B) To provide clearer, more specific error handling tailored to their application.

Question 34

What is a recommended practice when writing catch blocks in Java? A) Use generic Exception classes to catch all exceptions. B) Catch the most specific exception types first before more general types. C) Only catch RuntimeExceptions and ignore checked exceptions. D) Use empty catch blocks to pass all exceptions silently.

Answer 34

B) Catch the most specific exception types first before more general types.

Question 35

What does the list() method of the File class do in Java? A) It deletes files in the specified directory. B) It returns an array of strings naming the files and directories in the directory. C) It checks if the directory is writable. D) It creates a new file in the directory.

Answer 35

B) It returns an array of strings naming the files and directories in the directory.

Question 36

What should you do if an IOException occurs when reading from a file? A) Delete the file and create a new one. B) Retry the operation a fixed number of times before failing. C) Log the error and inform the user, possibly retrying or aborting the operation. D) Ignore the exception and continue to the next operation.

Answer 36

C) Log the error and inform the user, possibly retrying or aborting the operation.

Question 37

What is the advantage of using try-with-resources in Java? A) It automatically closes the resources after use. B) It handles all types of exceptions automatically. C) It improves the performance of I/O operations. D) It allows multiple resources to be opened simultaneously without closing them.

Answer 37

A) It automatically closes the resources after use.