In a scenario where you are developing a library for third-party users and want to ensure some of the internal data is not accessible to them but still serialized, which keyword/modifier would you use and how?
- Use the final keyword for internal data fields
- Use the private keyword for internal data fields
- Use the protected keyword for internal data fields
- Use the transient keyword for internal data fields
To ensure that internal data is not accessible to third-party users but can still be serialized, you can use the transient keyword for the internal data fields. This keyword prevents the fields from being serialized, providing data encapsulation while still allowing serialization for other non-sensitive fields. The other options (private, protected, and final) are related to access control and do not address the serialization aspect of the scenario.
Which block among try, catch, and finally is optional in exception handling?
- All of them
- catch
- finally
- try
In Java exception handling, the finally block is optional. The try block is used to enclose the code that may throw an exception, the catch block is used to handle the exception if it occurs, and the finally block is executed whether an exception occurs or not.
Which of the following methods in the Stream API can change the type of the elements in a stream?
- collect()
- filter()
- forEach()
- map()
The map() method in the Stream API is used to transform elements in a stream. It takes a function as an argument and applies that function to each element in the stream, producing a new stream with the transformed elements. This can change the type of elements in the stream if the mapping function converts them to a different type. The other methods listed do not change the type of elements in the stream.
In a scenario where you are designing a system that will store and manipulate confidential data (like passwords) which will be stored in the form of strings, how would you ensure that this sensitive data is not prone to security issues related to string handling?
- Use String and encrypt it
- Use String and mark it as 'final'
- Use StringBuilder and set 'secure' flag
- Use char[] to store passwords
To enhance security for sensitive data like passwords, you should use a char[] to store passwords instead of a String. This is because String objects are immutable and linger in memory, making them vulnerable to security risks. char[] can be overwritten, and you can zero it out after use. The other options do not provide similar security benefits.
________ is an interface providing thread safety without introducing concurrency overhead for each individual read/write operation.
- ConcurrentHashMap
- ConcurrentHashSet
- ConcurrentMap
- SynchronizedMap
In Java, the ConcurrentMap interface provides thread safety without introducing excessive concurrency overhead for each read/write operation. It allows multiple threads to read and write concurrently while maintaining data integrity. Other options, like SynchronizedMap and ConcurrentHashSet, have different characteristics in terms of thread safety and performance.
ReentrantLock belongs to the ______ package in Java.
- java.lang
- java.sync
- java.thread
- java.util.concurrent
ReentrantLock is part of the java.util.concurrent package in Java. It's a synchronization mechanism used for controlling access to critical sections of code by multiple threads.
If you do not specify any access level modifier, the default access level will be ________.
- package-private
- private
- protected
- public
If you do not specify any access level modifier in Java, the default access level will be "package-private" or sometimes referred to as "default." This means that the class, method, or variable is accessible within the same package.
The Character class in Java is used to wrap a value of the primitive data type ________.
- byte
- char
- float
- int
The Character class in Java is used to wrap a value of the primitive data type "char." This allows you to work with characters as objects, which can be useful in certain situations, such as when dealing with collections that require objects.
What is the role of FileWriter and FileReader in character streams when dealing with file I/O?
- FileWriter and FileReader are used for binary data, not text data.
- FileWriter and FileReader are used interchangeably, depending on whether you read or write data.
- FileWriter is used for reading text data, and FileReader is used for writing text data.
- FileWriter is used for writing text data to a file, and FileReader is used for reading text data.
FileWriter is used for writing text data to a file, while FileReader is used for reading text data from a file. These classes are specifically designed for character-based I/O operations and are suitable for working with text files. They automatically handle character encoding, making them convenient for text-based file operations.
Which of the following is the default value of an int variable declared as an instance variable?
- 0
- 1
- -1
- The default value depends on the specific situation.
In Java, the default value of an instance variable of type int is 0. This is true for all numeric types in Java. The other options are not the default values for int instance variables.