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A lambda expression can't specify type parameters, so it's not generic. However, a functional interface associated with lambda expression is generic. In this case, the target type of lambda expression has determined by the type of argument(s) specified when a functional interface reference is declared.
Lambda expression is an anonymous method (method without a name) that has used to provide the inline implementation of a method defined by the functional interface while a method reference is similar to a lambda expression that refers a method without executing it.
A lambda expression is a short block of code which takes in parameters and returns a value. Lambda expressions are similar to methods, but they do not need a name and they can be implemented right in the body of a method.
To summarize: If the purpose of the lambda expression is solely to pass a parameter to an instance method, then you may replace it with a method reference on the instance. If the pass-through is to a static method, then you may replace it with a method reference on the class.
You can't use a lambda expression for a functional interface, if the method in the functional interface has type parameters. See section §15.27.3 in JLS8:
A lambda expression is compatible [..] with a target type T if T is a functional interface type (§9.8) and the expression is congruent with the function type of [..] T. [..] A lambda expression is congruent with a function type if all of the following are true:
- The function type has no type parameters.
- [..]
Using method reference, i found other way to pass the argument:
List<String> list = Arrays.asList("a", "b", "c");
sort(list, Comparable::<String>compareTo);
Just point compiler the proper version of generic Comparator with
(Comparator<String>)
So the answer will be
sort(list, (Comparator<String>)(a, b) -> a.compareTo(b));
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