In this Java Tutorial we are going to discuss Java 8’s modification to the Java Collections API. The Java Collections Framework is being enhanced in order to get the benefits out of the latest Java 8 Feature that is Closures. If you are new to the concept of Java Closures or Lambda Expressions, I recommend you go through my previous post: Introduction to Java Closures – Lambda Expressions.Java Lambda Expressions would surely change some of our programming habits and also the way we look at the language, including the various Java APIs. When a feature like Lambda Expression is added to a programming language, it becomes extremely important to utilize the new feature to empower the overall programming model along with the existing set of libraries. With addition of Closures to Java, the existing Java Collection Framework will start looking weaker and outdated. The Java Collections framework was introduced in Java 1.2, and since then its core interfaces have never been changed. This is because, the Java Collections framework is so widely used, that any changes to it will surely broke many existing functionalities, and that’s why it is not easy to completely rewrite the Java Collections API. There was another option to keep the existing Collections API as is, and add an additional Lambda Expression friendly version of the API, but that would lead to tremendous amount of changes in the existing code, which depends upon the Collections API. Also applications will have to maintain two different versions of the library, and what if somebody wants to use a mix of old and new features? To overcome these challenges, Java 8 has added new set of methods to the existing collection classes and interfaces. Having these methods under the belt, the Java Collections framework will work as it used to be; and will also have an additional potential to support Java’s Lambda Expressions or Closures.