Learn about the best practices for concurrency in Java to ensure your multi-threaded applications are efficient, synchronized, and error-free. Concurrency in Java is the ability of multiple threads to ...

单例模式是一种创建型设计模式， 它的核心思想是保证一个类只有一个实例，并提供一个全局访问点来访问这个实例。 只有一个实例的意思是，在整个应用程序中，只存在该类的一个实例对象，而不是创建多个相同类型的对象。 全局访问点的意思是，为了让 ...

A Context provides access to information about the application state. It provides Activities, Fragments, and Services access to resource files, images, themes/styles, and external directory locations.