1 /*

     2  * Copyright (c) 2015, 2019, 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.

     8  *

     9  * This code is distributed in the hope that it will be useful, but WITHOUT

    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12  * version 2 for more details (a copy is included in the LICENSE file that

    13  * accompanied this code).

    14  *

    15  * You should have received a copy of the GNU General Public License version

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18  *

    19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    20  * or visit www.oracle.com if you need additional information or have any

    21  * questions.

    22  *

    23  */

    24 

    25 import sun.hotspot.WhiteBox;

    26 

    27 public class LockStringTest extends Thread {

    28     static String lock;

    29     static boolean done;

    30     static WhiteBox wb = WhiteBox.getWhiteBox();

    31 

    32     public static void main(String[] args) throws Exception {

    33 

    34         if (wb.areSharedStringsIgnored()) {

    35             System.out.println("The shared strings are ignored");

    36             System.out.println("LockStringTest: PASS");

    37             return;

    38         }

    39 

    40         if (!wb.isShared(LockStringTest.class)) {

    41             throw new RuntimeException("Failed: LockStringTest class is not shared.");

    42         }

    43 

    44         // Note: This class is archived. All string literals (including the ones used in this class)

    45         // in all archived classes are interned into the CDS shared string table.

    46 

    47         doTest("StringLock", false);

    48         doTest("", true);

    49 

    50         // The following string has a 0 hashCode. Calling String.hashCode() could cause

    51         // the String.hash field to be written into, if so make sure we don't functionally

    52         // break.

    53         doTest("\u0121\u0151\u00a2\u0001\u0001\udbb2", true);

    54     }

    55 

    56     private static void doTest(String s, boolean hasZeroHashCode) throws Exception {

    57         lock = s;

    58         done = false;

    59 

    60         if (!wb.isShared(lock)) {

    61             throw new RuntimeException("Failed: String \"" + lock + "\" is not shared.");

    62         }

    63 

    64         if (hasZeroHashCode && lock.hashCode() != 0) {

    65             throw new RuntimeException("Shared string \"" + lock + "\" should have 0 hashCode, but is instead " + lock.hashCode());

    66         }

    67 

    68         String copy = new String(lock);

    69         if (lock.hashCode() != copy.hashCode()) {

    70             throw new RuntimeException("Shared string \"" + lock + "\" does not have the same hashCode as its non-shared copy");

    71         }

    72 

    73         new LockStringTest().start();

    74 

    75         synchronized(lock) {

    76             while (!done) {

    77                 lock.wait();

    78             }

    79         }

    80         System.gc();

    81         System.out.println("LockStringTest: PASS");

    82     }

    83 

    84     public void run() {

    85         String shared = "LiveOak";

    86         synchronized (lock) {

    87             for (int i = 0; i < 100; i++) {

    88                 new String(shared);

    89                 System.gc();

    90                 try {

    91                     sleep(5);

    92                 } catch (InterruptedException e) {}

    93             }

    94             done = true;

    95             lock.notify();

    96         }

    97     }

    98 }