Design pattern

[Walter Thizo]

Hi developers

i am busy with the course OO analysis and design ,so my problem is i don't understand design pattern such as Singleton,Adapt er and Observer anyone with practical explanation ,i will appreciate the answer

[sicarie]

Well, what do you understand about each?

What don't you understand about each?

For instance, the Singleton. What is the definition of a Singleton? What is an example of one? When would you want to use it? When would you not?