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Java / JVM Architecture (Java21) Interview questions

What are the types of class loaders in JVM?

The JVM uses a small hierarchy of class loaders, each responsible for a different part of the classpath, and each (except the Bootstrap loader) has a parent it can delegate to.

Class LoaderLoads
Bootstrap ClassLoaderCore JDK classes (java.lang.*, java.util.*) from the JDK's own modules, implemented natively.
Platform ClassLoaderPlatform/JDK-supplied modules that are not part of the core bootstrap set (formerly called the Extension ClassLoader).
Application (System) ClassLoaderClasses from the application classpath or module path.
Custom ClassLoaderUser-defined loaders, e.g. for plugin systems or hot-reloading frameworks.

In Java 21, this model is unchanged since the module system arrived in Java 9: all three built-in loaders extend the same internal BuiltinClassLoader base.

Which class loader loads core classes like java.lang.String?
The Platform ClassLoader was previously known as the:

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