IV26337: ALTERNATE HASH ALGORITHM SUPPORT FOR HASH RELATED COLLECTION MAP S

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
  .
  

Local fix

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=n.
  

Problem conclusion

• This defect will be fixed in:
  5.0.0 SR14
  .
  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 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 5 CLASS LI

• Fixed component ID

  620500130

Applicable component levels

• R500 PSY

     UP