In Java, a final class is a class that is declared using the "final" keyword, which means that it cannot be extended or inherited by other classes. Final classes are useful for preventing inheritance, overriding, and creating constant variables and final methods.

Some key characteristics of final classes in Java include:

• Inflexibility: Final classes cannot be extended or inherited by other classes, making them inflexible.

• Wrapper classes: All wrapper classes in Java, such as String and Integer, are final classes.

• Security: Final classes can provide security by preventing the leaking of sensitive data.

To create a final class in Java, simply add the final keyword as a prefix to the class declaration. For example, the syntax for creating a final class named "className" would be:

final class className {
    // Body of class
}