| /* |
| * Copyright 2000-2014 JetBrains s.r.o. |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package org.jetbrains.annotations; |
| |
| import java.lang.annotation.*; |
| |
| /** |
| * An element annotated with {@link Nullable} claims {@code null} value is perfectly <em>valid</em> |
| * to return (for methods), pass to (parameters) or hold in (local variables and fields). |
| * Apart from documentation purposes this annotation is intended to be used by static analysis tools |
| * to validate against probable runtime errors or element contract violations. |
| * <br> |
| * By convention, this annotation applied only when the value should <em>always</em> be checked against {@code null} |
| * because the developer could do nothing to prevent null from happening. |
| * Otherwise, too eager {@link Nullable} usage could lead to too many false positives from static analysis tools. |
| * <br> |
| * For example, {@link java.util.Map#get(Object key)} should <em>not</em> be annotated {@link Nullable} because |
| * someone may have put not-null value in the map by this key and is expecting to find this value there ever since. |
| * <br> |
| * On the other hand, the {@link java.lang.ref.Reference#get()} should be annotated {@link Nullable} because |
| * it returns {@code null} if object got collected which can happen at any time completely unexpectedly. |
| * |
| * @author max |
| */ |
| @Documented |
| @Retention(RetentionPolicy.CLASS) |
| @Target({ElementType.METHOD, ElementType.FIELD, ElementType.PARAMETER, ElementType.LOCAL_VARIABLE}) |
| public @interface Nullable { |
| String value() default ""; |
| } |