1 /*
2 * Copyright (c) 2021, 2022, 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.misc;
27
28 import java.util.concurrent.locks.ReentrantLock;
29
30 /**
31 * A reentrant mutual exclusion lock for internal use. The lock does not
32 * implement {@link java.util.concurrent.locks.Lock} or extend {@link
33 * java.util.concurrent.locks.ReentrantLock} so that it can be distinguished
34 * from lock objects accessible to subclasses of {@link java.io.Reader} and
35 * {@link java.io.Writer} (it is possible to create a Reader that uses a
36 * lock object of type ReentrantLock for example).
37 */
38 public class InternalLock {
39 private static final boolean CAN_USE_INTERNAL_LOCK;
40 static {
41 String s = System.getProperty("jdk.io.useMonitors");
42 if (s != null && (s.isEmpty() || s.equals("true"))) {
43 CAN_USE_INTERNAL_LOCK = false;
44 } else {
45 CAN_USE_INTERNAL_LOCK = true;
46 }
47 }
48
49 private final ReentrantLock lock;
50
51 private InternalLock() {
52 this.lock = new ReentrantLock();
53 }
54
55 /**
56 * Returns a new InternalLock or null.
57 */
58 public static InternalLock newLockOrNull() {
59 return (CAN_USE_INTERNAL_LOCK) ? new InternalLock() : null;
60 }
61
62 /**
63 * Returns a new InternalLock or the given object.
64 */
65 public static Object newLockOr(Object obj) {
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1 /*
2 * Copyright (c) 2021, 2024, 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.misc;
27
28 import java.util.concurrent.locks.ReentrantLock;
29
30 /**
31 * A reentrant mutual exclusion lock for internal use. The lock does not
32 * implement {@link java.util.concurrent.locks.Lock} or extend {@link
33 * java.util.concurrent.locks.ReentrantLock} so that it can be distinguished
34 * from lock objects accessible to subclasses of {@link java.io.Reader} and
35 * {@link java.io.Writer} (it is possible to create a Reader that uses a
36 * lock object of type ReentrantLock for example).
37 */
38 public class InternalLock {
39 private static final boolean CAN_USE_INTERNAL_LOCK;
40 static {
41 String s = System.getProperty("jdk.io.useMonitors");
42 if (s != null && s.equals("false")) {
43 CAN_USE_INTERNAL_LOCK = true;
44 } else {
45 CAN_USE_INTERNAL_LOCK = false;
46 }
47 }
48
49 private final ReentrantLock lock;
50
51 private InternalLock() {
52 this.lock = new ReentrantLock();
53 }
54
55 /**
56 * Returns a new InternalLock or null.
57 */
58 public static InternalLock newLockOrNull() {
59 return (CAN_USE_INTERNAL_LOCK) ? new InternalLock() : null;
60 }
61
62 /**
63 * Returns a new InternalLock or the given object.
64 */
65 public static Object newLockOr(Object obj) {
|