NonNull.java

/*******************************************************************************
 * Copyright (c) 2011, 2013 Stephan Herrmann and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     Stephan Herrmann - initial API and implementation
 *     IBM Corporation - bug fixes
 *******************************************************************************/
package ch.elexis.core.jdt;

import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.LOCAL_VARIABLE;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.ElementType.PARAMETER;

import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * Qualifier for a type in a method signature or a local variable declaration: The entity (return
 * value, parameter, field, local variable) whose type has this annotation can never have the value
 * <code>null</code> at runtime.
 * <p>
 * This has two consequences:
 * <ol>
 * <li>Dereferencing the entity is safe, i.e., no <code>NullPointerException</code> can occur at
 * runtime.</li>
 * <li>An attempt to bind a <code>null</code> value to the entity is a compile time error.</li>
 * </ol>
 * For the second case, diagnostics issued by the compiler should distinguish three situations:
 * <ol>
 * <li>Nullness of the value can be statically determined, the entity is definitely bound from
 * either of:
 * <ul>
 * <li>the value <code>null</code>, or</li>
 * <li>an entity with a {@link Nullable @Nullable} type.</li>
 * </ul>
 * </li>
 * <li>Nullness cannot definitely be determined, because different code branches yield different
 * results.</li>
 * <li>Nullness cannot be determined, because other program elements are involved for which null
 * annotations are lacking.</li>
 * </ol>
 * </p>
 * 
 * @since 1.0
 */
@Documented
@Retention(RetentionPolicy.CLASS)
@Target({
	FIELD, METHOD, PARAMETER, LOCAL_VARIABLE
})
public @interface NonNull {
	// marker annotation with no members
}