Java SE 8 Programmer II Sample Test Questions
1. Which control flow statement allows you to repeat a block of code a specific number of times based on a counter variable?
a) if b) while c) for d) switch
Answer: c) for
Explanation: The for loop is specifically designed for iterating a block of code a predetermined number of times. It uses a counter variable that is initialized, incremented/decremented, and compared with a condition to control the number of repetitions.
Code Example:
for (int i = 1; i <= 5; i++) {
System.out.println("Iteration " + i);
}
This code will print "Iteration 1" to "Iteration 5" on the console.
2. Which control flow statement allows you to repeat a block of code indefinitely as long as a condition remains true?
a) if b) while c) for d) switch
Answer: b) while
Explanation: The while loop repeatedly executes a block of code as long as the specified condition evaluates to true. It checks the condition before each iteration, allowing for indefinite repetition until the condition becomes false.
Code Example:
int num = 10;
while (num > 0) {
System.out.println(num);
num--;
}
This code will print numbers from 10 to 1 on the console, decrementing num in each iteration.
. Which control flow statement allows you to choose between different code blocks based on the value of a variable?
a) if b) while c) for d) switch
Answer: a) if
Explanation: The if statement evaluates a condition and executes a specific block of code if the condition is true. It can also have an optional else block to execute code if the condition is false.
Code Example:
int age = 20;
if (age >= 18) {
System.out.println("You are eligible to vote.");
} else {
System.out.println("You are not eligible to vote.");
}
This code checks if the user's age is 18 or more and prints a corresponding message.
4. Which control flow statement allows you to choose between multiple code blocks based on the value of a variable, using a more concise syntax compared to multiple if-else statements?
a) if b) while c) for d) switch
Answer: d) switch
Explanation: The switch statement is used to select a specific block of code based on the value of a variable. It uses case labels to match different values and provides a more efficient way to handle multiple choices.
Code Example:
String day = "Monday";
switch (day) {
case "Monday":
System.out.println("It's a workday!");
break;
case "Saturday":
case "Sunday":
System.out.println("It's the weekend!");
break;
default:
System.out.println("Invalid day");
}
This code checks the day of the week and prints a corresponding message.
5. Which control flow statement allows you to skip the current iteration of a loop and jump to the next iteration?
a) if b) while c) for d) continue
Answer: d) continue
Explanation: The continue statement skips the remaining code in the current iteration of a loop and immediately jumps to the next iteration. It's useful for conditionally skipping certain iterations within a loop.
Code Example:
for (int i = 1; i <= 10; i++) {
if (i % 2 == 0) {
continue; // Skip even numbers
}
System.out.println(i);
}
This code prints only odd numbers from 1 to 10.
Exception Handling:
1. Which keyword is used to define a block of code that might throw an exception?
a) catch b) finally c) throws d) try
Answer: d) try
Explanation: The try block is used to enclose code that might potentially throw an exception. If an exception occurs within the try block, the program attempts to handle it using the corresponding catch blocks.
2. Which keyword is used to handle an exception thrown by the try block?
a) catch b) finally c) throws d) try
Answer: a) catch
Explanation: The catch block is used to handle specific types of exceptions that might be thrown within the try block. Each catch block can handle a specific exception type or its subclasses.
3. Which keyword is used to execute code regardless of whether an exception occurs in the try block?
a) catch b) finally c) throws d) try
Answer: b) finally
Explanation: The finally block is always executed, whether an exception occurs in the try block or not. It's commonly used to release resources (like closing files or connections) regardless of the program's execution flow.
Input/Output (Streams)
1. Which class in Java represents a stream of bytes that can be used for reading data from files or other sources?
a) InputStream b) OutputStream c) FileReader d) FileWriter
Answer: a) InputStream
Explanation: The InputStream class is the base class for all input streams in Java. It provides methods for reading raw bytes from various sources like files, network connections, or other input devices.
2. Which class in Java is used to write text data to a file?
a) InputStream b) OutputStream c) FileReader d) FileWriter
Answer: d) FileWriter
Explanation: The FileWriter class is used to write text data to a file. It provides methods like write() and write(String) to write characters or strings to the file.
Multithreading
- What is a thread in Java?
a) A separate program that can run independently.
b) A lightweight process within a program that can execute concurrently.
c) A way to share data between multiple programs.
d) A method for managing memory allocation.
Answer: b) A lightweight process within a program that can execute concurrently.
Explanation: A thread is a smaller unit of execution within a program that can run alongside other threads. This allows for concurrent execution of tasks within the same program.
2. Which of the following methods is used to start a thread in Java?
a) start() b) run() c) begin() d) execute()
Answer: a) start()
Explanation: The start() method is used to initiate the execution of a thread. Once called, the thread becomes active and starts running concurrently with other threads in the program.
3. What is the difference between a thread and a process?
- a) Threads are independent programs, while processes are smaller units within a program.
- b) Threads share the same memory space, while processes have separate memory spaces.
- c) Threads are faster to create and manage than processes.
- d) All of the above. Answer: c) Threads are faster to create and manage than processes. Explanation: Threads are lightweight compared to processes and share the same memory space within a program. This makes them faster and more efficient for managing concurrent tasks.
4. What is synchronization in multithreading?
a) A mechanism to ensure that multiple threads access shared resources safely and avoid conflicts.
b) A way to prioritize the execution of different threads.
c) A method for stopping threads from running.
d) A technique for sharing data between different processes.
Answer: a) A mechanism to ensure that multiple threads access shared resources safely and avoid conflicts.
Explanation: Synchronization is crucial in multithreading to prevent data corruption and unexpected behavior when multiple threads access shared resources like variables or objects.
5. What is a deadlock in multithreading?
a) A situation where two or more threads are waiting for each other to release resources, causing them to be stuck indefinitely.
b) A state where a thread has a high priority and can't be interrupted.
c) An error that occurs when a thread tries to access a resource that is already locked by another thread.
d) A method for debugging thread issues.
Answer: a) A situation where two or more threads are waiting for each other to release resources, causing them to be stuck indefinitely.
Explanation: A deadlock occurs when multiple threads are waiting for each other to release resources they hold, leading to a situation where none of them can proceed. This can be a major issue in multithreaded applications.
JDBC
- What is the primary purpose of the JDBC API in Java?
a) To provide a web development framework for Java applications.
b) To enable communication and interaction with relational databases from Java programs.
c) To manage and manipulate files and directories within the Java environment.
d) To handle network communication and data transfer between Java applications.
Answer: b) To enable communication and interaction with relational databases from Java programs.
Explanation: JDBC stands for Java Database Connectivity. It provides a set of classes and interfaces that allow Java programs to connect to, query, and manipulate data stored in relational databases like MySQL, Oracle, and PostgreSQL.
2. Which of the following classes is used to establish a connection to a database in JDBC?
a) DriverManager b) Connection c) Statement d) ResultSet
Answer: a) DriverManager
Explanation: The DriverManager class is responsible for managing database drivers and establishing connections to databases. It provides methods like getConnection() to connect to a database using the appropriate driver and connection URL.
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