Method reference to instance method from class type vs Method reference to instance method from instance

user1169587 :

Method reference to instance method from instance

// compile successfully, out is instance, println is instance method
Consumer<String> c = System.out::println; 

Method reference to instance method from class type

// compile fail, PrintStream is class type, println is instance method
Consumer<String> c = PrintStream::println; 

why Consumer<String> c = PrintStream::println fail?

Bohemian :

But!

BiConsumer<PrintStream, String> c = PrintStream::println; // compiles!

Method references to the class have an implicit first parameter of the instance. This is similar to Method whose invoke() method’s first parameter is the instance.