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∟Annotation Statements and Declarationshtml

This chapter provides tutorial notes on annotation. Topics include declaring new annotation type; using 'interface' for annotations; specifying default values to annotation elements; shorthand format of annotation invocation with a single element or no element; obtaining annotation information at runtime using getAnnotations() method; predefined annotations in Java.

What Is Annotation

Use "interface" as Annotation

Default Values for Annotation Elements

Single-Element Annotation Invocation

No-Element (Marker) Annotation Invocation

getAnnotations() Method - Annotation APIs

Predefined Annotation Types

Takeaways:

• Annotation is a programming facility that allows you to associates additional information with a program construct like class, method, variable, etc.
• "@interface" statements are used to declare new annotation types, which are special interface types.
• Annotation elements are methods declared in interfaces.
• "default" keyword is used to specify default values to annotation elements.
• Annotation invocation with a single element named "value" can be shorthanded as @Type(value).
• Annotation invocation with no element (called marker annotation) can be shorthanded as @Type.
• Java provides getAnnotations() method and other APIs to help you obtain annotation information at runtime.
• Java provides a number of predefined annotation types. Most of them are used by the compiler to prevent programming mistakes.

Table of Contents

 About This Book

 JDK - Java Development Kit

 Execution Process, Entry Point, Input and Output

 Primitive Data Types and Literals

 Control Flow Statements

 Bits, Bytes, Bitwise and Shift Operations

 Managing Bit Strings in Byte Arrays

 Reference Data Types and Variables

 Enum Types and Enum Constants

 StringBuffer - The String Buffer Class

 System Properties and Runtime Object Methods

 Generic Classes and Parameterized Types

 Generic Methods and Type Inference

 Lambda Expressions and Method References

 Java Modules - Java Package Aggregation

 Execution Threads and Multi-Threading Java Programs

 ThreadGroup Class and "system" ThreadGroup Tree

 Synchronization Technique and Synchronized Code Blocks

 Deadlock Condition Example Programs

 Garbage Collection and the gc() Method

 Assert Statements and -ea" Option

►Annotation Statements and Declarations

 Java Related Terminologies

 Archived Tutorials

 References

 Full Version in PDF/EPUB

Annotation Statements and Declarations - Updated in 2024, by Herong Yang