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[fonbot.git] / src / org / eclipse / jdt / annotation / NonNull.java
1 /*******************************************************************************
2 * Copyright (c) 2011, 2012 Stephan Herrmann and others.
3 * All rights reserved. This program and the accompanying materials
4 * are made available under the terms of the Eclipse Public License v1.0
5 * which accompanies this distribution, and is available at
6 * http://www.eclipse.org/legal/epl-v10.html
7 *
8 * Contributors:
9 * Stephan Herrmann - initial API and implementation
10 * IBM Corporation - bug fixes
11 *******************************************************************************/
12 package org.eclipse.jdt.annotation;
13
14 import static java.lang.annotation.ElementType.LOCAL_VARIABLE;
15 import static java.lang.annotation.ElementType.METHOD;
16 import static java.lang.annotation.ElementType.PARAMETER;
17
18 import java.lang.annotation.Documented;
19 import java.lang.annotation.Retention;
20 import java.lang.annotation.RetentionPolicy;
21 import java.lang.annotation.Target;
22
23 /**
24 * Qualifier for a type in a method signature or a local variable declaration:
25 * The entity (return value, parameter, local variable) whose type has this
26 * annotation can never have the value <code>null</code> at runtime.
27 * <p>
28 * This has two consequences:
29 * <ol>
30 * <li>Dereferencing the entity is safe, i.e., no <code>NullPointerException</code> can occur at runtime.</li>
31 * <li>An attempt to bind a <code>null</code> value to the entity is a compile time error.</li>
32 * </ol>
33 * For the second case, diagnostics issued by the compiler should distinguish three situations:
34 * <ol>
35 * <li>Nullness of the value can be statically determined, the entity is definitely bound from either of:
36 * <ul><li>the value <code>null</code>, or</li>
37 * <li>an entity with a {@link Nullable @Nullable} type.</li></ul></li>
38 * <li>Nullness cannot definitely be determined, because different code branches yield different results.</li>
39 * <li>Nullness cannot be determined, because other program elements are involved for which
40 * null annotations are lacking.</li>
41 * </ol>
42 * </p>
43 * @since 1.0
44 */
45 @Documented
46 @Retention(RetentionPolicy.CLASS)
47 @Target({ METHOD, PARAMETER, LOCAL_VARIABLE })
48 public @interface NonNull {
49 // marker annotation with no members
50 }
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