Benefits of a Collections Framework

• It reduces programming effort: By providing useful data structures and algorithms, a collections framework frees you to concentrate on the important parts of your program, rather than the low-level plumbing required to make it work. By facilitating interoperability among unrelated APIs (as described below), the collections framework frees you from writing oodles of adapter objects or conversion code to connect APIs.
• It increases program speed and quality: The collections framework does this primarily by providing high-performance, high-quality implementations of useful data structures and algorithms. Also, because the various implementations of each interface are interchangeable, programs can be easily tuned by switching collection implementations. Finally, because you're freed from the drudgery of writing your own data structures, you'll have more time to devote to improving the quality and performance of the rest of the program.
• It allows interoperability among unrelated APIs: The collections interfaces will become the "lingua franca" by which APIs pass collections back and forth. If my network administration API furnishes a Collection of node names, and your GUI toolkit expects a Collection of column headings, our APIs will interoperate seamlessly even though they were written independently.
• It reduces the effort to learn and use new APIs: Many APIs naturally take collections on input and output. In the past, each such API had a little "sub-API" devoted to manipulating its collections. There was little consistency among these ad-hoc collections sub-APIs, so you had to learn each one from scratch and it was easy to make mistakes when using them. With the advent of standard collections interfaces, the problem goes away.
• It reduces effort to design new APIs: This is the flip-side of the previous advantage: designers and implementers don't have to reinvent the wheel each time they create an API that relies on collections. They just use the standard collections interfaces.
• It fosters software reuse: New data structures that conform to the standard collection interfaces are by nature reusable. The same goes for new algorithms that operate on objects that implement these interfaces.