Lesson: Arrays and Enumerated Types

From the Java virtual machine's perspective, arrays and enumerated types (or enums) are just classes. Many of the methods in Class may be used on them. Reflection provides a few specific APIs for arrays and enums. This lesson uses a series of code samples to describe how to distinguish each of these objects from other classes and operate on them. Various errors are also be examined.

Arrays

Arrays have a component type and a length (which is not part of the type). Arrays may be maniuplated either in their entirety or component by component. Reflection provides the java.lang.reflect.Array class for the latter purpose.

• Identifying Array Types describes how to determine if a class member is a field of array type
• Creating New Arrays illustrates how to create new instances of arrays with simple and complex component types
• Getting and Setting Arrays and Their Components shows how to access fields of type array and individually access array elements
• Troubleshooting covers common errors and programming misconceptions

Enumerated Types

Enums are treated very much like ordinary classes in reflection code. Class.isEnum() tells whether a Class represents and enum. Class.getEnumConstants() retrieves the enum constants defined in an enum. java.lang.reflect.Field.isEnumConstant() indicates whether a field is an enumerated type.

• Examining Enums illustrates how to retrieve an enum's constants and any other fields, constructors, and methods
• Getting and Setting Fields with Enum Types shows how to set and get fields with an enum constant value
• Troubleshooting describes common errors associated with enums