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Java 8 - Stream.collect() Example

The collect() method of Stream class can be used to accumulate elements of any Stream into a Collection. In Java 8, you will often write code which converts a Collection e.g. List or Set to Stream and then applies some logic using functional programming methods like the filter, map, flatMap and then converts the result back to the Collection e.g. List, Set or Map. In this last part, the collect() method of Stream helps. It accepts a Collector to accumulate elements of Stream into specified Collection. The Collector class provides different methods e.g. toList(), toSet(), toMap(), and toConcurrentMap() to collect the result of Stream into List, Set, Map, and ConcurrentMap in Java.

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Hello there, if you are someone who is learning programming and coding by yourself and looking for some awesome resources then you have come to the right place. In this article, I am going to share 25 websites you can use to learn the code for free from the comfort of your office and home.

1. plurasight.com
One of the best website to learn any technology or IT courses e.g. programming language like Java, web development framework e.g. Spring Framework, Hibernate etc. It's also now acquired CodeSchool which earlier allows you to learn web technologies by doing it. I use this website to learn a lot of cool stuff in no time.

What is double colon (::) operator in Java 8 - Example

The double colon (::) operator is known as the method reference in Java 8. Method references are expressions which have the same treatment as a lambda expression, but instead of providing a lambda body, they refer to an existing method by name. For example, to print all elements of the list you can use the forEach() method as follows

list.stream.forEach( s-> System.out.println(s));

but here you can replace lambda expression with method reference to improve readability as shown below:

list.stream.forEach( System.out::println);

You can use method reference or double colon operator to refer a static method, an instance method, or a constructor.