LoadJavaClass — load and set up a Java class for use from the Wolfram Language

JavaClass — expression that represents a Java class

JavaNew — create a Java object of a specified class

JavaObject — expression that represents a Java class

MakeJavaObject, MakeJavaExpr — create a Java object that represents an expression

Constructors, Methods, Fields — information about classes

JavaObjectQ — whether an expression is a valid Java object reference

InstanceOf — whether an object is an instance of a certain class or interface

SameObjectQ — whether two JavaObject expressions reference the same Java object

LoadedJavaObjects, LoadedJavaClasses — list all Java objects or classes in use

ClassName — get the fully qualified name of a class

GetClass, ParentClass — get the JavaClass representing a Java object's class or parent class

ReturnAsJavaObject — return an object reference instead of its value

JavaObjectToExpression — convert an object reference into its value

ImplementJavaInterface — implement a Java interface via callbacks to the Wolfram Language