What is a ClassLoader?

In the Java programming language, a classloader is a program that loads Java classes into the Java Virtual Machine (JVM) at runtime. When you run a Java program, the JVM loads the class or classes that contain the main method, and then executes the main method. However, the JVM may also need to load additional classes as the program runs, and it does this using classloaders.

There are several different types of classloaders in the Java runtime, including the bootstrap classloader, the extension classloader, and the system classloader. The bootstrap classloader is responsible for loading the core Java classes that are part of the Java SE platform, such as java.lang and java.util. The extension classloader loads classes from the extension directories specified in the Java runtime, and the system classloader loads classes from the classpath specified when the JVM is launched.

Classloaders are an important part of the Java runtime because they allow the JVM to load classes dynamically at runtime, rather than requiring all classes to be loaded upfront. This makes it possible to run Java programs that use large numbers of classes, or that make use of classes that are not known at compile time.

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