| package org.checkerframework.checker.nullness.qual; |
| |
| import java.lang.annotation.Documented; |
| import java.lang.annotation.ElementType; |
| import java.lang.annotation.Retention; |
| import java.lang.annotation.RetentionPolicy; |
| import java.lang.annotation.Target; |
| import org.checkerframework.framework.qual.MonotonicQualifier; |
| import org.checkerframework.framework.qual.SubtypeOf; |
| |
| /** |
| * Indicates that once the field (or variable) becomes non-null, it never becomes null again. There |
| * is no guarantee that the field ever becomes non-null, but if it does, it will stay non-null. |
| * |
| * <p>Example use cases include lazy initialization and framework-based initialization in a |
| * lifecycle method other than the constructor. |
| * |
| * <p>A monotonically non-null field has these two properties: |
| * |
| * <ol> |
| * <li>The field may be assigned only non-null values. |
| * <li>The field may be re-assigned as often as desired. |
| * </ol> |
| * |
| * <p>When the field is first read within a method, the field cannot be assumed to be non-null. |
| * After a check that a {@code @MonotonicNonNull} field holds a non-null value, all subsequent |
| * accesses <em>within that method</em> can be assumed to be non-null, even after arbitrary external |
| * method calls that might access the field. |
| * |
| * <p>{@code @MonotonicNonNull} gives stronger guarantees than {@link Nullable}. After a check that |
| * a {@link Nullable} field holds a non-null value, only accesses until the next non-{@link |
| * org.checkerframework.dataflow.qual.SideEffectFree} method is called can be assumed to be |
| * non-null. |
| * |
| * <p>To indicate that a {@code @MonotonicNonNull} or {@code @Nullable} field is non-null whenever a |
| * particular method is called, use {@code @}{@link RequiresNonNull}. |
| * |
| * <p>Final fields are treated as MonotonicNonNull by default. |
| * |
| * @see EnsuresNonNull |
| * @see RequiresNonNull |
| * @see MonotonicQualifier |
| * @see org.checkerframework.checker.nullness.NullnessChecker |
| * @checker_framework.manual #nullness-checker Nullness Checker |
| */ |
| @Documented |
| @Retention(RetentionPolicy.RUNTIME) |
| @Target(ElementType.TYPE_USE) |
| @SubtypeOf(Nullable.class) |
| @MonotonicQualifier(NonNull.class) |
| public @interface MonotonicNonNull {} |