The ClassLoader is a built-in mechanism in the Java Virtual Machine (JVM) that is responsible for loading class files into the JVM at runtime. It is an essential component of the Java language that enables the JVM to dynamically load and execute Java classes.
The ClassLoader is responsible for finding and loading the bytecode of a class into memory. It's also responsible for resolving the class dependencies, linking the class and initializing the class at runtime. When a class is first used, its bytecode is loaded into memory by the ClassLoader, and the JVM can then execute the class's methods.
In Java, a ClassLoader is the part of the Java Runtime Environment (JRE) responsible for loading classes into the JVM dynamically at runtime. This works based on the parent-delegation model where it first delegates class-loading requests to its parent ClassLoader and then to itself in an attempt to load the class. ClassLoaders are examples like Bootstrap ClassLoader, Extension ClassLoader, and Application ClassLoader.
A ClassLoader in Java is a very important component of the Java Virtual Machine (JVM), which dynamically loads classes during runtime when they are required. It thus does not require loading all classes at program startup, hence saving efficiency and flexibility. The ClassLoader follows a parent-delegation hierarchy for security and to avoid conflicts between classes. Then is the Bootstrap ClassLoader, loading core Java classes from the rt.jar or system class paths, followed by Extension ClassLoader in charge of classes loaded from lib/ext directory and specified extensions and finally Application ClassLoader loading user-defined application specific classes in a user class path. Developers can also create custom ClassLoaders to implement specialized class-loading mechanisms, making them invaluable for tasks like dynamic module loading or frameworks such as Spring and Hibernate.