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copied!<p>You can create your own annotations and apply them to your own classes.</p> <p>If you specify that an annotation is detectable at runtime, you can process it easily with reflection.</p> <p>For example, you could use something like this to print the name of each field in a class that has been marked with the <em>Funky</em> annotation:</p> <pre><code>for (Field someField : AnnotatedClass.getClass().getDeclaredFields()) { if (someField.isAnnotationPresent(Funky.class)) { System.out.println("This field is funky: " + someField.getName()); } } </code></pre> <p>The code to declare the <em>Funky</em> annotation would look something like this:</p> <pre><code>package org.foo.annotations; @Retention(RetentionPolicy.RUNTIME) @Target(ElementType.FIELD) public @interface Funky { } </code></pre> <p>Here's a class that uses the annotation:</p> <pre><code>package org.foo.examples; import org.foo.annotations.Funky; public class AnnotatedClass { @Funky private String funkyString; private String nonFunkyString; @Funky private Integer funkyInteger; private Integer nonFunkyInteger; } </code></pre> <p>Here's some <a href="http://docs.oracle.com/javase/6/docs/technotes/guides/language/annotations.html" rel="nofollow">more reading on Annotations</a>.</p> <p>Here are the javadocs for the classes used above:</p> <ul> <li><a href="http://docs.oracle.com/javase/6/docs/api/java/lang/annotation/Retention.html" rel="nofollow">Retention annotation</a></li> <li><a href="http://docs.oracle.com/javase/6/docs/api/java/lang/annotation/RetentionPolicy.html" rel="nofollow">RetentionPolicy enum</a></li> <li><a href="http://docs.oracle.com/javase/6/docs/api/java/lang/annotation/Target.html" rel="nofollow">Target annotation</a></li> <li><a href="http://docs.oracle.com/javase/6/docs/api/java/lang/reflect/Field.html" rel="nofollow">Field class</a></li> <li><a href="http://docs.oracle.com/javase/6/docs/api/java/lang/reflect/AccessibleObject.html#isAnnotationPresent%28java.lang.Class%29" rel="nofollow">isAnnotationPresent() method</a></li> <li><a href="http://docs.oracle.com/javase/6/docs/api/java/lang/Class.html#getDeclaredFields%28%29" rel="nofollow">getDeclaredFields() method</a></li> </ul> <hr> <p>I'm trying to understand your car example, but I'm not sure I follow what you want.</p> <p>If you had a list of objects (Jaguar, Porche, Ferrari, Kia) that extend Car and are marked with various car-related annotations, you could create an object that filters the list based on annotations. </p> <p>The code might look like this:</p> <pre><code>@WorldsFinestMotorCar class Jaguar extends Car { // blah blah } @BoringCar class Porche extends Car { // blah blah } @BoringCar class Ferrari extends Car { // blah blah } @IncredibleCar class Kia extends Car { // blah blah } </code></pre> <p>You could implement an <em>AnnotationFilter</em> class that removes cars from the list that do not have a certain annotation. </p> <p>It might look something like this:</p> <pre><code>List<Car> carList = getListOfRandomCars(); AnnotationFilter<Car> annoFilter = new AnnotationFilter<Car>(BoringCar.class); List<Car> boringCars = annoFilter.filter(carList); </code></pre> <p>Is that what you want to do?</p> <p>If so, it can definitely be done.</p> <p>The implementation for AnnotationFilter might look something like this:</p> <pre><code>public class AnnotationFilter<T> { private Class filterAnno; public AnnotationFilter(Class a) { filterAnno = a; } public List<T> filter(List<T> inputList) { if (inputList == null || inputList.isEmpty()) { return inputList; } List<T> filteredList = new ArrayList<T>(); for (T someT : inputList) { if (someT.getClass().isAnnotationPresent(filterAnno)) { filteredList.add(someT); } } return filteredList; } } </code></pre> <p>If that's not what you're after, a specific example would be helpful.</p>

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