What happens when java program starts?

Question

Recently have been touched Java classloaders and suddenly recognized that do not fully understand what happens step-by-step when someone calls

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Answer 1

•Who and how decides which classes should be loaded at startup and which once needed?

we need to understand the fundamentals of java class loading. Initially bootstrap classloader (it is implemented natively as part of the VM itself) is responsible for loading core system classes. Then there are other class loaders as well like Extension, system, user-defined(optional) class loaders which decide when and how classes should be loaded. Fundamentals of class loading