Fields (The Java™ Tutorials > The Reflection API > Members)

Documentation The Java™ Tutorials Hide TOC Members Fields Obtaining Field Types Retrieving and Parsing Field Modifiers Getting and Setting Field Values Troubleshooting Methods Obtaining Method Type Information Obtaining Names of Method Parameters Retrieving and Parsing Method Modifiers Invoking Methods Troubleshooting Constructors Finding Constructors Retrieving and Parsing Constructor Modifiers Creating New Class Instances Troubleshooting Trail: The Reflection API Lesson: Members Home Page > The Reflection API > Members « Previous • Trail • Next »

The Java Tutorials have been written for JDK 8. Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available.See Dev.java for updated tutorials taking advantage of the latest releases.See Java Language Changes for a summary of updated language features in Java SE 9 and subsequent releases.See JDK Release Notes for information about new features, enhancements, and removed or deprecated options for all JDK releases.

Fields

A field is a class, interface, or enum with an associated value. Methods in the java.lang.reflect.Field class can retrieve information about the field, such as its name, type, modifiers, and annotations. (The section Examining Class Modifiers and Types in the Classes lesson describes how to retrieve annotations.) There are also methods which enable dynamic access and modification of the value of the field. These tasks are covered in the following sections:

• Obtaining Field Types describes how to get the declared and generic types of a field
• Retrieving and Parsing Field Modifiers shows how to get portions of the field declaration such as public or transient
• Getting and Setting Field Values illustrates how to access field values
• Troubleshooting describes some common coding errors which may cause confusion

When writing an application such as a class browser, it might be useful to find out which fields belong to a particular class. A class's fields are identified by invoking Class.getFields(). The getFields() method returns an array of Field objects containing one object per accessible public field.

A public field is accessible if it is a member of either:

• this class
• a superclass of this class
• an interface implemented by this class
• an interface extended from an interface implemented by this class

A field may be a class (instance) field, such as java.io.Reader.lock , a static field, such as java.lang.Integer.MAX_VALUE , or an enum constant, such as java.lang.Thread.State.WAITING.

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