| 1. 11. 3. 指定一个保留政策 |
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A retention policy determines at what point an annotation is discarded. |
- SOURCE: annotation retained only in the source file and is discarded during compilation.
- CLASS: annotation stored in the .class file during compilation, not available in the run time.
- RUNTIME: annotation stored in the .class file and available in the run time.
- They are defined java.lang.annotation.RetentionPolicy enumeration.
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A retention policy is specified using Java's built-in annotations: @Retention. |
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@Retention(retention-policy)
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the default policy is CLASS. |
MyAnnotation uses @Retention to specify the RUNTIME retention policy. |
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import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
// A simple annotation type.
@Retention(RetentionPolicy.RUNTIME)
@interface MyAnnotation {
String stringValue();
int intValue();
}
public class MainClass {
// Annotate a method.
@MyAnnotation(stringValue = "Annotation Example", intValue = 100)
public static void myMethod() {
}
}
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