examples of Design Patterns

Question

I was asked in a job interview to give examples of design patterns and how they are used in the JVM implementation? I was stumped -- can anyone suggest answers so I'll know what to say if I'm ever asked again?

A very straightforward one would be the Observer Pattern with [Observable](http://docs.oracle.com/javase/7/docs/api/java/util/Observable.html). — Jeroen Vannevel, Jan 29 '14 at 08:31
possible duplicate of [Examples of GoF Design Patterns](http://stackoverflow.com/questions/1673841/examples-of-gof-design-patterns) — Boris the Spider, Jan 29 '14 at 08:32

score 4 · Accepted Answer · answered Jan 29 '14 at 08:36

Java File IO library is based on Decorator pattern.
Java Collections sort() uses Strategy pattern.
There is inbuilt support for Observer Pattern in JDK, By using Observable class and Observer interface, you can have Observer Pattern
Singleton Pattern in used in Runtime class, where you can have only one object of type 'Runtime', by accessing getRuntime() method.

examples of Design Patterns

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