A sparse array is one in which the elements do not have contiguous indexes starting at 0

Sometimes it’s important to have only one instance for a class. For example, in a system there should be only one window manager (or only a file system or only a print spooler). Usually singletons are used for centralized management of internal or external resources and they provide a global point of access to themselves.

Design principles provide high level guidelines to design better software applications. They do not provide implementation guidelines and are not bound to any programming language.

Use Annotation writes Mysql and Oracle’ sql in Mybatis

Use batch update sql has an Error in Mysql Database.

Markdown is a lightweight and easy-to-use syntax for styling all forms of writing on the GitHub platform.

What’s a version control system?

Getting Started with GitHub Pages

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