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.
What is the primary difference between StringBuilder and StringBuffer classes in Java?
- StringBuffer is not synchronized, making it faster but not thread-safe.
- StringBuilder has more methods for manipulating strings.
- StringBuilder is immutable, while StringBuffer is mutable.
- StringBuilder is synchronized, making it thread-safe but potentially slower.
The primary difference is that StringBuilder is not synchronized, making it faster but not thread-safe, while StringBuffer is synchronized, making it thread-safe but potentially slower. Immutable means unchangeable, which is not true for either class.
Which access modifier allows a member to be accessed from within its own class only?
- default (no modifier)
- private
- protected
- public
In Java, the private access modifier restricts access to the member to within the same class only. It is used to encapsulate the implementation details and hide them from external classes. The other options allow varying degrees of access to the member from outside the class.
Which interface or class should a class use or extend to create a new thread in Java?
- Executor
- Runnable
- Thread
- java.lang
In Java, to create a new thread, a class should implement the Runnable interface. The Runnable interface defines a single abstract method, run(), which should be overridden to provide the code that the new thread will execute. The other options are not used for directly creating a new thread.
What is the impact of using PrintWriter in file handling without automatic line flushing?
- It buffers data and may not immediately write it to the file.
- It ensures efficient memory usage and high-speed writing to the file.
- It has no impact on file handling.
- It throws an error if used without automatic line flushing.
PrintWriter in Java buffers data by default, which means it doesn't immediately write to the file. Without automatic line flushing, you must manually flush the buffer (using flush()), or it may not write data until the buffer is full or the program exits. This buffering can improve performance but may lead to unexpected behavior if you forget to flush.