Method reference is used to refer method of the functional interface. It is a compact and easy form of a lambda expression. Each time when you are using a lambda expression to just referring a method, you can replace your lambda expression with a method reference.
Below are a few examples of method reference:
(o) -> o.toString();
can become:
Object::toString();
A method reference can be identified by a double colon separating a class or object name and the name of the method. It has different variations such as constructor reference:
String::new;
Static method reference:
String::valueOf;
Bound instance method reference:
str::toString;
Unbound instance method reference:
String::toString;
