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  1. package name.dhruba.kb.concurrent.striping;
  2.  
  3. public class IntrinsicStripedLockProvider {
  4.  
  5.     private static final int DEFAULT_NUMBER_OF_LOCKS = 2048;
  6.  
  7.     private static final int DOUG_LEA_BLACK_MAGIC_OPERAND_1 = 20;
  8.     private static final int DOUG_LEA_BLACK_MAGIC_OPERAND_2 = 12;
  9.     private static final int DOUG_LEA_BLACK_MAGIC_OPERAND_3 = 7;
  10.     private static final int DOUG_LEA_BLACK_MAGIC_OPERAND_4 = 4;
  11.  
  12.     private final Object[] locks;
  13.     private final int numberOfLocks;
  14.  
  15.     public IntrinsicStripedLockProvider() {
  16.         this(DEFAULT_NUMBER_OF_LOCKS);
  17.     }
  18.  
  19.     public IntrinsicStripedLockProvider(int numberOfLocks) {
  20.  
  21.         if ((numberOfLocks & (numberOfLocks - 1)) != 0) {
  22.             throw new IllegalArgumentException("Lock number must be a power of two: "
  23.                     + numberOfLocks);
  24.         }
  25.  
  26.         if (numberOfLocks == 0) {
  27.             throw new IllegalArgumentException("A zero size striped lock provider "
  28.                     + "does not have useful semantics.");
  29.         }
  30.  
  31.         this.numberOfLocks = numberOfLocks;
  32.         this.locks = new Object[numberOfLocks];
  33.         for (int i = 0; i < numberOfLocks; i++) {
  34.             locks[i] = new Object();
  35.         }
  36.  
  37.     }
  38.  
  39.     public Object getLockForKey(Object key) {
  40.         int lockNumber = selectLock(key, numberOfLocks);
  41.         return locks[lockNumber];
  42.     }
  43.  
  44.     private static int selectLock(Object key, int numberOfLocks) {
  45.         return key == null ? 0 : hash(key) & (numberOfLocks - 1);
  46.     }
  47.  
  48.     private static int hash(Object object) {
  49.         int h = object.hashCode();
  50.         h ^= (h >>> DOUG_LEA_BLACK_MAGIC_OPERAND_1) ^ (h >>> DOUG_LEA_BLACK_MAGIC_OPERAND_2);
  51.         return h ^ (h >>> DOUG_LEA_BLACK_MAGIC_OPERAND_3) ^ (h >>> DOUG_LEA_BLACK_MAGIC_OPERAND_4);
  52.     }
  53.  
  54. }
Compilation error #stdin compilation error #stdout 0s 0KB
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stdin
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Standard input is empty
compilation info 
Main.java:3: error: class IntrinsicStripedLockProvider is public, should be declared in a file named IntrinsicStripedLockProvider.java
public class IntrinsicStripedLockProvider {
       ^
1 error
stdout
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Standard output is empty
https://ideone.com/C2f1NC
language:
Java (HotSpot 12)
created:
9 years ago
visibility:
secret

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