The ______ method of the Lock interface is used to acquire the lock.
- acquire()
- lock()
- tryLock()
- unlock()
The lock() method of the Lock interface is used to acquire the lock. It blocks until the lock is available and then acquires it. The unlock() method is used to release the lock. The acquire() and tryLock() methods are not part of the standard Lock interface in Java.
Consider a scenario where you have a large number of short-lived asynchronous tasks. Which type of ExecutorService would you consider using and why?
- CachedThreadPoolExecutor: A thread pool that dynamically creates and recycles threads.
- FixedThreadPoolExecutor: A fixed-size thread pool with a specific number of threads.
- ScheduledThreadPoolExecutor: A thread pool for scheduling tasks at a fixed rate or delay.
- SingleThreadPoolExecutor: A single-threaded ExecutorService.
In this scenario, the CachedThreadPoolExecutor is suitable. It dynamically adjusts the number of threads based on the workload, making it efficient for short-lived tasks. SingleThreadPoolExecutor and FixedThreadPoolExecutor have limitations for such cases, and ScheduledThreadPoolExecutor is designed for scheduling tasks, not managing short-lived tasks.
The ________ interface is used to execute SQL stored procedures.
- CallableStatement
- Connection
- PreparedStatement
- Statement
In JDBC, the CallableStatement interface is used to execute SQL stored procedures. It allows you to call stored procedures that may take parameters and return values. Statement is used for executing regular SQL statements, Connection is used for establishing database connections, and PreparedStatement is used for executing parameterized SQL queries.
The ________ data type in Java can store decimal numbers up to 15 decimal places.
- BigDecimal
- double
- float
- long
In Java, the BigDecimal data type is used to store decimal numbers with precision up to 15 decimal places. It is commonly used in financial and scientific applications where high precision is required. The float and double types have limited precision and are not suitable for this purpose.
Externalizable interface extends ______ interface and adds two methods into it.
- Cloneable
- Externalization
- ObjectInput/Output
- Serializable
The Externalizable interface in Java extends the ObjectInput and ObjectOutput interfaces and adds two methods into it: writeExternal and readExternal. These methods are used for customized serialization of objects. The other options are not related to the Externalizable interface.
In which version of Java were Lambda expressions introduced?
- Java 6
- Java 7
- Java 8
- Java 9
Lambda expressions were introduced in Java 8. They are a significant feature that simplifies the syntax for writing anonymous functions and enhances the readability and conciseness of code in Java.
Lambda expressions eliminate the need for ________.
- Anonymous inner classes
- Arrays
- Inheritance
- Interfaces
Lambda expressions eliminate the need for anonymous inner classes. Before lambda expressions were introduced in Java, anonymous inner classes were used to implement single-method interfaces, like Runnable or ActionListener. Lambda expressions provide a more concise and expressive way to define such implementations, reducing the verbosity of code.
How does the compiler resolve the "+" operator when used with different data types (e.g., String and int)?
- It performs the operation based on the type of the first operand and ignores the second operand's type.
- It throws a compilation error because the + operator cannot be used with different data types.
- It throws a runtime error because the + operator is ambiguous with different data types.
- It uses type conversion to promote one of the operands to the type of the other operand, and then performs the operation.
It uses type conversion to promote one of the operands to the type of the other operand, and then performs the operation. For example, if you add a string and an int, the int is converted to a string, and string concatenation is performed. If you add two integers, normal addition is performed.
Imagine you are developing a text editor that frequently alters strings (like undo, redo, replace, cut, copy, and paste operations). Which class(es) would you utilize for efficient memory and performance management?
- String and PhantomReference
- StringBuffer and SoftReference
- StringBuilder and WeakReference
- StringJoiner and ReferenceQueue
In a text editor, where efficient memory and performance management are crucial, StringBuilder is used for in-place string manipulation, and WeakReference helps in memory management by allowing objects to be garbage collected when not strongly referenced. StringBuffer is thread-safe but may not provide the best performance. The other options are not suitable for such scenarios.
What happens when the join() method is called on a thread?
- The calling thread will wait for the specified thread to finish.
- The specified thread will be paused but continue executing later.
- The specified thread will be terminated immediately.
- The specified thread will wait for the calling thread to finish.
When the join() method is called on a thread in Java, the calling thread will wait for the specified thread to finish its execution. This is often used to ensure that a thread completes its task before the calling thread proceeds. It's a mechanism for thread synchronization.