Standard functional interfaces

Let's create our own function using several standard functional interfaces.

Implement a ternaryOperator method that accepts a predicate condition, and two functions ifTrue and ifFalse and returns a function. The returning function takes an argument, and checks if the condition predicate is true for this argument, and if it is — applies the ifTrue function to the argument, otherwise, it applies ifFalse function.

Here is an example:

Predicate<Object> condition = Objects::isNull;
Function<Object, Integer> ifTrue = obj -> 0;
Function<CharSequence, Integer> ifFalse = CharSequence::length;
Function<String, Integer> safeStringLength = ternaryOperator(condition, ifTrue, ifFalse);

In the example above, the resulting function returns the length of a string if the reference to the string is not null, otherwise, it returns 0.

Note, it can be collapsed into a single line, but for clarity, additional variables are used.