GeezerVison

I have introduced the method reference in the previous tutorial, in this tutorial, I introduce you another new concept: constructor reference. Like the method reference, the constructor reference is used to abbreviate the Lambda Expression expression. How is it in details?

Suppose you are working with a Lambda Expression like this:

Java

1	(args) -> new ClassName(args)

In this expression Lambda Expression, the body part we have only a code for initializing a new object with the constructor having or not having argument parameters.

To be concise, we can use the constructor reference as follows:

Java

1	ClassName::new

For the example of this constructor reference, I will use some of the interfaces in the java.util.function package.

With the constructor without parameters, we will use the Supplier interface with the Lambda Expression expression as follows:

Java

1	Supplier<List<String>> s = () -> new ArrayList<>();

Rewrite with the constructor reference:

Java

1	Supplier<List<String>> s = ArrayList::new;

Given a constructor with a parameter, we will use the Function interface with the Lambda Expression expression as follows:

Java

1	Function<String, Integer> f = s -> new Integer(s);

Rewrite with the constructor reference:

Java

1	Function<String, Integer> f = Integer::new;

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