The key difference between a synchronized block and a synchronized method is that synchronized blocks can be used to synchronize multiple sections of code within the same method, providing more fine-grained control over synchronization. In contrast, synchronized methods synchronize the entire method. Synchronized methods are not necessarily more efficient than synchronized blocks; their efficiency depends on the specific use case.

You can create a stream from a collection in Java using the stream() method. This method is available on all collections and provides a way to obtain a stream that allows you to perform various stream operations on the elements of the collection. Options 2 to 4 are not used to create streams but for other stream operations.

The keyword "private" is used to apply restrictions on class members. It restricts access to only within the same class, making it the most restrictive access modifier in Java.

CSS can be applied to style JavaFX components by attaching external CSS files to the application using the addStylesheet() method. This allows for a separation of concerns between the application logic and its styling. It provides flexibility and maintainability in designing the user interface. Inline CSS can also be used for individual components, but it's not the standard way to style JavaFX applications.

In JavaFX, the show() method is used to display a stage. When you create a JavaFX application, you typically create a Stage object and use its show() method to make it visible. The other options are not valid methods for displaying a stage.

A key characteristic of a lambda expression in Java is that it can capture local variables from its enclosing scope. This allows lambda expressions to use values from the surrounding context, making them useful for creating concise and expressive code.

In a Book class for a library system, you would define properties like title, author, ISBN, and publication date as they represent essential book attributes. Get and set methods are used for encapsulation and data integrity, and the toString method helps in displaying the book's details. The other options include irrelevant properties and methods.

The Runnable interface in Java can be implemented using lambda expressions. It's a functional interface with a single abstract method run(). This allows you to use lambda expressions for tasks that can be executed concurrently. Lambda expressions simplify the creation of anonymous classes for such tasks.

The expression 5 > 3 is true because 5 is indeed greater than 3. The other options are not true: 10 != 10 is false (since 10 is equal to 10), (4 + 6) * 2 == 20 is true (since 10 equals 20), and "Java" == "java" is false because string comparison in Java is case-sensitive.

Lambda expressions in Java are primarily used to define the implementation of functional interfaces. A functional interface is an interface that has only one abstract method. Lambda expressions provide a concise way to implement the single abstract method of such interfaces.

Parameterized constructors can be utilized in a user profile management system to quickly initialize user objects during the registration process. These constructors accept user details (e.g., username, email, password) as parameters, allowing you to create user objects with pre-populated data, making registration more efficient and straightforward.

The collect() method is a terminal operation in the Stream API. It is used to accumulate the elements of a stream into a collection, such as a List or Set. Terminal operations are those that trigger the processing of the stream and produce a final result.