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 }