What classes are included with Java?

Package java. lang ClassDescriptionCompilerThe Compiler class is provided to support Java-to-native-code compilers and related services.DoubleThe Double class wraps a value of the primitive type double in an object.Enum<E extends Enum<E>>This is the common base class of all Java language enumeration types.Package java.lang – Oracle Help Center docs.oracle.com › javase › docs › api › java › lang › package-summary

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Why is Java all in classes?

So because there’s nothing but classes in Java (except the few Java primitive types, like int, float, …) we have to define the main method, the starting point for a java application, inside a class. The main method is a normal static method that behaves just like any other static method.

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