1 package checkers.quals; 2 3 import static java.lang.annotation.ElementType.FIELD; 4 import java.lang.annotation.*; 5 6 /** 7 * Declares that the field may not be accessed if the receiver is of the 8 * specified qualifier type (or any supertype). 9 * 10 * This property is verified by the checker that type-checks the {@code 11 * when} element value qualifier. 12 * 13 * <p><b>Example</b> 14 * Consider a class, {@code Table}, with a locking field, {@code lock}. The 15 * lock is used when a {@code Table} instance is shared across threads. When 16 * running in a local thread, the {@code lock} field ought not to be used. 17 * 18 * You can declare this behavior in the following way: 19 * 20 * <pre><code> 21 * class Table { 22 * private @Unused(when=LocalToThread.class) final Lock lock; 23 * ... 24 * } 25 * </code></pre> 26 * 27 * The checker for {@code @LocalToThread} would issue an error for the following code: 28 * 29 * <pre> @LocalToThread Table table = ...; 30 * ... table.lock ...; 31 * </pre> 32 * 33 */ 34 @Documented 35 @Retention(RetentionPolicy.RUNTIME) 36 @Target({FIELD}) 37 public @interface Unused { 38 /** 39 * The field that is annotated with @Unused may not be accessed via a 40 * receiver that is annotated with the "when" annotation. 41 */ 42 Class<? extends Annotation> when(); 43 } 44
