1 /*
 2  * Copyright (c) 2001, 2021, 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 
26 package jdk.internal.reflect;
27 
28 import jdk.internal.vm.annotation.Stable;
29 
30 import java.lang.reflect.InvocationTargetException;
31 import java.util.Objects;
32 
33 /** Delegates its invocation to another ConstructorAccessorImpl and can
34     change its delegate at run time. */
35 
36 class DelegatingConstructorAccessorImpl extends ConstructorAccessorImpl {
37     // initial non-null delegate
38     private final ConstructorAccessorImpl initialDelegate;
39     // alternative delegate: starts as null;
40     // only single change from null -> non-null is guaranteed
41     @Stable
42     private ConstructorAccessorImpl altDelegate;
43 
44     DelegatingConstructorAccessorImpl(ConstructorAccessorImpl delegate) {
45         initialDelegate = Objects.requireNonNull(delegate);
46     }
47 
48     public Object newInstance(Object[] args)
49       throws InstantiationException,
50              IllegalArgumentException,
51              InvocationTargetException
52     {
53         return delegate().newInstance(args);
54     }
55 
56     private ConstructorAccessorImpl delegate() {
57         var d = altDelegate;
58         return  d != null ? d : initialDelegate;
59     }
60 
61     void setDelegate(ConstructorAccessorImpl delegate) {
62         altDelegate = Objects.requireNonNull(delegate);
63     }
64 }