Object, which is the root of the class hierarchy, and
Class, instances of which represent classes at run time.
Frequently it is necessary to represent a value of primitive type as if it were an object. The wrapper classes
Double serve this purpose. An object of type
Double , for example, contains a field whose type is double, representing that value in such a way that a reference to it can be stored in a variable of reference type. These classes also provide a number of methods for converting among primitive values, as well as supporting such standard methods as equals and hashCode. The
Void class is a non-instantiable class that holds a reference to a
Class object representing the type void.
Math provides commonly used mathematical functions such as sine, cosine, and square root. The classes
StringBuilder similarly provide commonly used operations on character strings.
System provide "system operations" that manage the dynamic loading of classes, creation of external processes, host environment inquiries such as the time of day, and enforcement of security policies.
java.nio.charset.Charsetclass describes the naming conventions for character encodings as well as the set of standard encodings that must be supported by every implementation of the Java platform.
Instances of the class
A class loader is an object that is responsible for loading classes.
Represents a run-time module, either
A layer of modules in the Java virtual machine.
Controls a module layer.
An element in a stack trace, as returned by
Thrown to indicate that a method has been called by an inappropriate caller.
Thrown when creating a module layer fails.
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