What is the most used pattern in java.io?

Question

I was asked this question recently during my job interview, and I couldn't answer it. So, what is the most used pattern in java.io and how is it used? What are other patterns used in common java libraries?

Answer 1

I guess they wanted to hear about the Decorator pattern which can be found in the various Streams, Readers and Writers.

Other patterns (small selection):

• Observer pattern in the swing libraries
• Factory pattern in the javax.xml.parsers packages
• Iterator pattern, used in collections

I'm pretty sure that one can find examples for almost all patterns listed on this wikipedia page in the Java SDK.