Java 类加载机制详细介绍

一、类加载器

　　类加载器（ClassLoader），顾名思义，即加载类的东西。在我们使用一个类之前，JVM需要先将该类的字节码文件（.class文件）从磁盘、网络或其他来源加载到内存中，并对字节码进行解析生成对应的Class对象，这就是类加载器的功能。我们可以利用类加载器，实现类的动态加载。

二、类的加载机制

　　在Java中，采用双亲委派机制来实现类的加载。那什么是双亲委派机制？在Java Doc中有这样一段描述：

The ClassLoader class uses a delegation model to search for classes and resources. Each instance of ClassLoader has an associated parent class loader. When requested to find a class or resource, a ClassLoader instance will delegate the search for the class or resource to its parent class loader before attempting to find the class or resource itself. The virtual Machine's built-in class loader, called the "bootstrap class loader", does not itself have a parent but may serve as the parent of a ClassLoader instance.