The example given from the Oracle Doc linked is:
String[] stringArray = { "Barbara", "James", "Mary", "John", "Patricia", "Robert", "Michael", "Linda" };
Arrays.sort(stringArray, String::compareToIgnoreCase);
The lambda equivalent of
String::compareToIgnoreCase
would be
(String a, String b) -> a.compareToIgnoreCase(b)
The Arrays.sort()
method is looking for a comparator as its second argument (in this example). Passing String::compareToIgnoreCase
creates a comparator with a.compareToIgnoreCase(b)
as the compare method’s body. You then ask well what’s a
and b
. The first argument for the compare method becomes a
and the second b
. Those are the arbitrary objects, of the type String (the particular type).
Don’t understand?
- Make sure you know what a comparator is and how to implement it.
- Know what a functional interface is and how it affects lambdas in Java.
- A comparator is a functional interface that’s why the method reference becomes the body of the compare method inside the comparator object.
- Read the source below for another example at the bottom of the page.
Read more at the source:
http://moandjiezana.com/blog/2014/understanding-method-references/