IV25852: ALTERNATE HASH ALGORITHM SUPPORT FOR HASH RELATED COLLECTION MAPS

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APAR status

  • Closed as program error.

Error description

  • Error Message: An alternate hash algorithm for java.lang.String
    is introduced to avoid the hash collision in put/get operations
    of Hash related collection maps like Hashtable, HashMap, etc
    .
    Stack Trace: N/A
    .
    N/A
    

Local fix

  • N/A
    

Problem summary

  • The current hashing algorithm is more predictable and can cause
    hash collision in put/get operations of Hash related collection
    maps like Hashtable, HashMap, etc. The alternate hash
    implementation will avoid the hash collision by introducing a
    random factor.
    
    Due to the introduction of random factor, the order of retrieval
    of elements from the collection maps can differ when the new
    hash algorithm is used. As documented in the API specification,
    there is no guarantee as to the order of the map; in particular,
    it does not guarantee that the order will remain constant over
    time. Application should make sure that they removed any such
    dependency before enabling the alternate hash algorithm. By
    default, the new hashing algorithm is disabled. It will be in
    affect only when the map capacity reaches the hashing threshold
    which can be set using Java command line argument
    -Djdk.map.althashing.threshold=nn.
    

Problem conclusion

  • This defect will be fixed in:
    6.0.0 SR11
    6.0.1 SR3
    7.0.0 SR2
    .
    The JDK has been equipped with an alternate hash implementation
    which avoids the hash collision in put/get operations of Hash
    related collection maps.
    

Temporary fix

Comments

APAR Information

  • APAR number

    IV25852

  • Reported component name

    JAVA CLASS LIBS

  • Reported component ID

    620700130

  • Reported release

    600

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2012-08-07

  • Closed date

    2012-08-07

  • Last modified date

    2012-11-02

  • APAR is sysrouted FROM one or more of the following:

  • APAR is sysrouted TO one or more of the following:

Fix information

  • Fixed component name

    JAVA CLASS LIBS

  • Fixed component ID

    620700130

Applicable component levels

  • R600 PSY

       UP

  • R700 PSY

       UP



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Document information


More support for:

Runtimes for Java Technology
Java Class Libraries

Software version:

6.0

Reference #:

IV25852

Modified date:

2012-11-02

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