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, 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.

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.

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.

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.

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.

In Java, the switch statement supports fall-through behavior, meaning that when a case label is matched, the code will continue to execute the subsequent case labels unless interrupted by a break statement. This behavior allows multiple cases to be executed for a single condition match, making it important to use break to terminate the flow when needed.

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.

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.

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.