What is the return type of the map() function in Java Streams API?
- List
- Stream
- int
- void
The map() function in Java Streams API transforms the elements of a stream and returns a new stream of the transformed elements. Therefore, the return type of map() is Stream. It allows you to apply a function to each element and map them to a new value or type.
In Java, if an if statement does not have any braces {}, only the ________ line after the if condition is considered part of the if block.
- first
- last
- middle
- next
In Java, when an if statement does not have braces {}, only the first line of code immediately following the if condition is considered part of the if block. Any subsequent lines of code are executed outside of the if block. This can lead to unexpected behavior if not used carefully.
Which exception might be thrown when trying to create a new Socket instance?
- IOException
- NetworkException
- SocketCreationException
- SocketException
When attempting to create a new Socket instance, you may encounter an IOException if there's an issue with the network connection or if the host is unreachable. It's a common exception in socket programming. The other options are not standard exceptions related to socket creation.
How does Java determine which overloaded method to call?
- Java calls the method randomly, as it cannot determine which one to call.
- Java calls the method that exactly matches the arguments provided during the method call.
- Java calls the method with the fewest number of parameters.
- Java calls the method with the most number of parameters.
Java determines which overloaded method to call by examining the number and types of arguments provided during the method call. It looks for the method that exactly matches the provided arguments. If no exact match is found, it results in a compilation error.
Which JavaFX layout class allows you to arrange components in a resizable grid of rows and columns?
- BorderPane
- FlowPane
- GridPane
- HBox
The GridPane layout class in JavaFX is used to create a grid-based layout where components can be arranged in rows and columns. This layout is suitable for resizable grids, making it ideal for creating forms and other structured interfaces. Components can be placed in specific grid cells, allowing for precise positioning and alignment.
What is the output of the following code snippet: for(int i = 0; i < 5; i++) { System.out.print(i + " "); }?
- 0 1 2 3 4
- 0 1 2 3 4 5
- 1 2 3 4
- 1 2 3 4 5
The correct output is "0 1 2 3 4." This is because the loop initializes i to 0, iterates as long as i is less than 5, and increments i by 1 in each iteration. It prints the value of i followed by a space in each iteration. When i reaches 5, the loop terminates.
Which of the following statements about constructor overloading in Java is correct?
- Constructor overloading allows a class to have multiple constructors with the same name but different parameters.
- Constructor overloading is not supported in Java.
- Constructor overloading requires that all constructors have the same number of parameters.
- Constructor overloading can only be used in abstract classes.
a) is correct. Constructor overloading in Java enables a class to have multiple constructors with the same name but different parameters. This allows for creating objects with various initializations. b) and d) are incorrect statements. c) is also incorrect because the number of parameters can vary among overloaded constructors.
Which of the following states is not a valid thread state in Java?
- Blocked
- Running
- Sleeping
- Terminated
In Java, the valid thread states are Running, Blocked, Terminated, and Sleeping. "Running" is not a valid thread state because it's not used to describe the state of a thread in Java. A running thread is simply a thread that is currently executing its code.
Which method in the ExecutorService interface waits for all tasks to complete after a shutdown request?
- awaitShutdown()
- awaitTermination()
- isTerminated()
- shutdownNow()
The awaitTermination() method in the ExecutorService interface is used to wait for all tasks to complete after a shutdown request has been made using the shutdown() method. It blocks until all tasks have completed or the specified timeout has passed. The isTerminated() method checks if the ExecutorService has terminated but doesn't wait.
How can a developer prevent a field from being serialized?
- Mark the field as final.
- Mark the field as private.
- Mark the field as static.
- Mark the field as transient.
In Java, to prevent a field from being serialized, you can mark it as transient. When a field is marked as transient, it will not be included in the serialization process. The other options do not directly prevent serialization. Marking a field as final has no impact on serialization. Marking it as static means the field will be serialized. Marking it as private affects only access, not serialization.