--- /dev/null 2013-01-08 12:17:08.801456335 -0800 +++ new/src/share/classes/java/lang/FunctionalInterface.java 2013-01-08 14:01:56.000000000 -0800 @@ -0,0 +1,63 @@ +/* + * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved. + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. + * + * This code is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 only, as + * published by the Free Software Foundation. Oracle designates this + * particular file as subject to the "Classpath" exception as provided + * by Oracle in the LICENSE file that accompanied this code. + * + * This code is distributed in the hope that it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License + * version 2 for more details (a copy is included in the LICENSE file that + * accompanied this code). + * + * You should have received a copy of the GNU General Public License version + * 2 along with this work; if not, write to the Free Software Foundation, + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. + * + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA + * or visit www.oracle.com if you need additional information or have any + * questions. + */ + +package java.lang; + +import java.lang.annotation.*; + +/** + * Indicates that an interface type declaration is intended to be a + * functional interface as defined by the Java Language + * Specification. + * + * Conceptually, a functional interface has exactly one abstract + * method. Since {@linkplain java.lang.reflect.Method#isDefault() + * default methods} have an implementation, they are not abstract. If + * an interface declares an abstract method overriding one of the + * public methods of {@code java.lang.Object}, that also does + * not count toward the interface's abstract method count + * since any implementation of the interface will have an + * implementation from {@code java.lang.Object} or elsewhere. + * + *

Note that instances of functional interfaces can be created with + * lambda expressions, method references, or constructor references. + * + *

If a type is annotated with this annotation type, compilers are + * required to generate an error message unless: + * + *

+ * + * @jls 4.3.2. The Class Object + * @jls 9.8 Functional Interfaces + * @jls 9.4.3 Interface Method Body + * @since 1.8 + */ +@Documented +@Retention(RetentionPolicy.RUNTIME) +@Target(ElementType.TYPE) +public @interface FunctionalInterface {}