Single Abstract Method of java.util.function.Function Interface

D.

The correct answer is C: It accepts one argument and always produces a result of the same type as the argument.

The Function interface is a part of the java.util.function package introduced in Java 8, and it represents a function that takes one argument and produces a result. The Function interface has one abstract method called apply().

The signature of the apply() method is as follows:

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R apply(T t); 

Here, T represents the type of the input argument, and R represents the type of the output/result. The apply() method takes an argument of type T and returns a value of type R.

Therefore, option A is incorrect as it mentions that the apply() method returns void, but in reality, it returns a value of type R.

Option B is also incorrect as it mentions that the apply() method returns a boolean, but in reality, the return type R can be any data type and not just a boolean.

Option D is also incorrect as it mentions that the apply() method can return a result of any data type, which is not true as the return type is always of the same type as the argument.

Therefore, option C is the correct answer as it correctly describes that the apply() method accepts one argument and always produces a result of the same type as the argument.