1 /* 2 * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 package java.lang.invoke; 26 27 import java.lang.annotation.TrackableConstant; 28 29 /** 30 * Descriptor for an entry in the classfile constant pool. 31 * 32 * A {@linkplain Constable} should be defined entirely in terms of other 33 * {@linkplain Constable} types. The types {@link Integer}, {@link Long}, 34 * {@link Float}, {@link Double}, and {@link String} implement 35 * {@linkplain Constable}. Implementation classes should be value-based. 36 * 37 * Like names in the constant pool, names in a constant descriptor are independent 38 * of a class loader. When a {@linkplain Constable} is intrinsified, it is 39 * interpreted relative to the class loader that loaded the class in which the 40 * intrinsic appears (just like names that appear in that classes constant pool.) 41 * When resolved through the method {@link #resolveConstant}, an explicit 42 * {@link MethodHandles.Lookup} must be provided. 43 * 44 * The intrinsifiable methods in {@link Intrinsics} take {@linkplain Constable} 45 * arguments. 46 * 47 * @param <T> The type to which this constant pool entry resolves 48 * 49 * @see Constables 50 * @see Intrinsics 51 * @see TrackableConstant 52 */ 53 public interface Constable<T> { 54 /** 55 * Resolve this constant, relative to the provided lookup. 56 * @param lookup the lookup to use to resolve this constant 57 * @return the constant 58 * @throws ReflectiveOperationException if the constant refers to a class 59 * or member that does not exist, or is not accessible to the class described 60 * by {@code lookup} 61 */ 62 T resolveConstant(MethodHandles.Lookup lookup) throws ReflectiveOperationException; 63 }