在 Java 中高效使用锁的技巧(3)

				
 public class StrippingLock implements Runnable{ 
    private final Object[] locks; 
    private static final int N_LOCKS = 4; 
    private final String [] share ; 
    private int opNum; 
    private int N_ANUM; 

    public StrippingLock(int on, int anum) { 
        opNum = on; 
        N_ANUM = anum; 
        share = new String[N_ANUM]; 
        locks = new Object[N_LOCKS]; 
        for (int i = 0; i<N_LOCKS; i++) 
        locks[i] = new Object(); 
    } 

    public synchronized void put1(int indx, String k) { 
        share[indx] = k;    //acquire the object lock         
    } 

      
    public void put2(int indx, String k) { 
        synchronized (locks[indx%N_LOCKS]) { 
            share[indx] = k;    // acquire the corresponding lock 
        } 
    } 
    
    public void run() 
    { 
        //The expensive put 
        /*for (int i=0; i<opNum; i++) 
        { 
            put1(i%N_ANUM, Integer.toString(i+1)); 
        }*/ 
        //The cheap put 
        for (int i=0; i<opNum; i++) 
        { 
            put2(i%N_ANUM, Integer.toString(i+1)); 
        } 
    }    
 }
 
 results from JLM report 
 
 使用 put1 的结果
 
 MON-NAME [08121228] StrippingLock@D79962D8 (Object) 
 %MISS     GETS   NONREC     SLOW      REC    TIER2    TIER3 %UTIL AVER_HTM 
     0  4830690  4830690      460        0 229538313  5010789    18     2552  

 Execution Time: 5536 milliseconds 

 使用 put2 的结果
  
 MON-NAME [08121388] java/lang/Object@D79964B8 (Object) 
 %MISS     GETS   NONREC     SLOW      REC    TIER2    TIER3 %UTIL AVER_HTM  
     0  4591046  4591046     1517        0 151042525  3016162    13     1925  
     
 MON-NAME [08121330] java/lang/Object@D79964C8 (Object) 
 %MISS     GETS   NONREC     SLOW      REC    TIER2    TIER3 %UTIL AVER_HTM  
     0  1717579  1717579      523        0 50596994   958796     5     1901  
     
 MON-NAME [081213E0] java/lang/Object@D79964D8 (Object) 
 %MISS     GETS   NONREC     SLOW      REC    TIER2    TIER3 %UTIL AVER_HTM  
     0  1814296  1814296      536        0 58043786  1113454     5     1799  
     
 MON-NAME [08121438] java/lang/Object@D79964E8 (Object) 
 %MISS     GETS   NONREC     SLOW      REC    TIER2    TIER3 %UTIL AVER_HTM  
     0  3126427  3126427      901        0 96627408  1857005     9     1979  
     
 Execution Time: 1857  milliseconds
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