Consider a scenario where a very large number of string concatenation operations are being performed in a single-threaded application. Which class would be appropriate to use for string manipulation, and why?
- String
- StringBuffer
- StringBuilder
- StringJoiner
In a single-threaded application with frequent string concatenation, StringBuilder is the most suitable choice. It's efficient because it doesn't create new objects when you modify the string, which can save memory and reduce overhead. StringBuffer is also thread-safe but slightly slower due to synchronization. String creates a new string each time you modify it, and StringJoiner is used for joining strings, not efficient for concatenation.
The operator ______ is invalid in Java.
- $
- %
- +
- -
In Java, the dollar sign ($) is not a valid operator. It's used in variable names and identifiers but not as an operator. The other options (+, -, %) are valid arithmetic operators in Java.
In Java 8 and above, the ________ method can be used to perform a certain action for each element of a collection.
- applyActionToElement() Method
- forEach() Method
- iterate() Method
- processElement() Method
In Java 8 and above, the "forEach()" method is used to perform a specified action for each element of a collection. It provides a concise way to iterate through elements in a collection and apply a given action to each element. The other options do not represent the correct method for this purpose.
How does intrinsic locking in synchronized methods/blocks ensure thread safety?
- It allows all threads to execute synchronized code simultaneously.
- It doesn't affect thread safety.
- It prevents all threads from executing synchronized code simultaneously.
- It relies on hardware-specific instructions.
Intrinsic locking in synchronized methods/blocks ensures thread safety by preventing multiple threads from executing synchronized code simultaneously. When a thread enters a synchronized block, it acquires the lock associated with the synchronized object, preventing other threads from entering the same synchronized block until the lock is released. This ensures that only one thread can execute the synchronized code at a time, preventing data races and ensuring thread safety.
What will be the outcome if you try to execute a DML (Data Manipulation Language) operation using executeQuery() method?
- The DML operation will execute successfully, and the result set will be returned.
- A SQLException will be thrown, as executeQuery() is meant for querying data, not for DML operations.
- The DML operation will execute, but no result set will be returned.
- An UnsupportedOperationException will be thrown, indicating that executeQuery() cannot be used for DML operations.
When you try to execute a DML operation (such as INSERT, UPDATE, DELETE) using the executeQuery() method, option b is correct. It will throw a SQLException because executeQuery() is meant for querying data and returns a ResultSet, which is not applicable to DML operations. Options a and c are incorrect because they suggest that the DML operation can proceed, which is not the case. Option d is also incorrect; it does not represent the actual behavior of executeQuery().
What is the role of the ObjectOutputStream class in serialization?
- It handles user input for serialization
- It performs encryption on serialized data
- It reads objects from a stream
- It serializes objects into a byte stream
The ObjectOutputStream class in Java is used to serialize objects into a byte stream. It's responsible for writing the state of an object to the output stream. Conversely, ObjectInputStream is used for reading serialized objects from a stream. It is an essential part of Java's serialization mechanism.
Consider a scenario where you want to invert the sign of a numeric value only if a particular boolean condition is true. How can unary operators be utilized to achieve this without using an if statement?
- int invertedValue = (condition) ? -numericValue : numericValue;
- int invertedValue = (condition) ? numericValue : -numericValue;
- int invertedValue = -numericValue;
- int invertedValue = numericValue;
You can use the conditional (ternary) operator ? : to achieve this. If the condition is true, it negates the numericValue by using the unary minus operator. If false, it leaves the numericValue unchanged. Option 1 demonstrates this technique.
How can you securely serialize and deserialize objects to protect sensitive information during the process?
- Define custom serialization and deserialization logic with encryption and authentication mechanisms
- Employ access modifiers such as private and protected for fields and methods
- Ensure that classes are marked as final to prevent inheritance
- Use encryption techniques
To securely serialize and deserialize objects to protect sensitive information, you should use encryption techniques. Encrypting the data before serialization and decrypting it after deserialization ensures that the data remains confidential. While access modifiers and marking classes as final provide some level of security, they don't directly address the need for encryption. Custom logic with encryption and authentication is a comprehensive approach to security.
A ________ is a result-bearing computation that can be canceled and can compute the result asynchronously provided by ExecutorService.
- Callable
- ExecutorService
- Runnable
- Thread
A Callable in Java is a result-bearing computation that can be canceled and can compute the result asynchronously. It is typically used with ExecutorService to perform tasks that return values or throw exceptions.
What is the impact of using a SocketChannel in non-blocking mode over traditional blocking I/O socket communication?
- a. SocketChannel offers better performance with lower CPU usage.
- b. Non-blocking SocketChannel can handle only one connection at a time.
- c. Blocking I/O sockets are more suitable for high-throughput applications.
- d. Non-blocking SocketChannel improves data integrity.
Using SocketChannel in non-blocking mode (option a) can lead to improved performance with lower CPU usage compared to traditional blocking I/O sockets. Non-blocking SocketChannels can handle multiple connections concurrently. Option c is incorrect because non-blocking SocketChannels are often favored for high-throughput scenarios. Option d is not accurate as data integrity is not directly related to blocking or non-blocking mode.