A design pattern is a general solution to a common problem. The singleton pattern is used to restricts the instantiation of a class to one single object.

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Real live comparison:

If statement is like walking on the cliff, on each step you need to check your stability otherwise you may fall into abyss.

Try/catch block is like walking on the street, you don't have to care about the road on each step, only when there is an obstacle (something exceptional is happening).

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A system may contain multiple physical CPUs (central processing unit), and can contain one or more cores (processors). Also, each core can have multiple threads, usually 2. (Hyper-threading Technology from Intel CPUs).

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