BigDecimal is no longer effectively immutable

FULL PRODUCT VERSION :
java version "1.8.0_20"
Java(TM) SE Runtime Environment (build 1.8.0_20-b26)
Java HotSpot(TM) 64-Bit Server VM (build 25.20-b23, mixed mode)


A DESCRIPTION OF THE PROBLEM :
Calling BigDecimal.setScale now changes the underlying object sometimes. It is unclear under which conditions the bug manifests itself.

REGRESSION. Last worked in version 7u67

ADDITIONAL REGRESSION INFORMATION:
java version "1.8.0_20"
Java(TM) SE Runtime Environment (build 1.8.0_20-b26)
Java HotSpot(TM) 64-Bit Server VM (build 25.20-b23, mixed mode)


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the attached code. It should

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The program should print "Success!"
ACTUAL -
It throws an Exception

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
package ponder;

import java.math.BigDecimal;
import java.math.RoundingMode;

public class Bug
{
public static void main (String[] args) throws Exception
{
BigDecimal total = new BigDecimal ("258815507198903607775511093103396443816569106750031264155319238473795838680758514810110764742309284477206138527975952150289602995045050194333030191178778772026538699925775139201970526695485362661420908248887297829319881475178467494779683293036572059595504702727301324759997409522995072582369210284334718757260859794972695026582432867589093687280300148141501712013226636373167978223780290547640482160818746599330924736802844173226042389174403401903999447463440670236056324929325189403433689" +
".426167432065785331444814035799717606745777287606858873045971898862329763544687891847664736523584843544347118836628373041412918374550458884706686730726101338872517021688769782894793734049819222924171842793485919753186993388451909096042127903835765393729547730953942175461146061715108701615615142134282261293656760570061554783195726716403304101469782303957325142638493327692352838806741611887655695029948975509680496573999174402058593454203190963443179532640446352828089016874853634851387762579319853267317320515941105912189838719919259277721994880193541634872882180184303434360412344059435559680494807415573269199203376126242271766939666939316648575065702750502798973418978204972336924254702551350654650573582614211506856383897692911422458286912085339575875324832979140870119455620532272318122103640233069115700020760625493816902806241630788230268031695140687964931377988962507263990468276009750998066442971308866347136022907166625330623130307555914930120150437900510530537258665172619821272937026713977709974434967165159545592482710663639966781678268622620229577009317698254134914742098420792313931843709810905414336383757407675429663714210967924767434203021205270369316797752411974617662200898086335322218191674846795163102021505555508444216708745911194321674887527227200297039471799580744303346354057273540730643842091810899490590914195225087593013834388801018488174855060306804024894292757613618190472234110859436472645203753139820658279559340251226992556744343475086923568365637919479462424794554522865559888240039662899509652221329892034706445253487898044421278283079233226845124525434586324657471286953226255430662125870993375281512713207125720748163498642795960457639954616530163959004770092547297392499137383176609646505351001304840762905826237024982330597805063521162285806541220110524989649256399233792799406995068469271941269511818994954109392839548141262324660472253632382325038836831429045617036015122388070240133760858500132713255407855625837956886349324981003917084922808187223285051144454915441134217743066575863563572152133978905444998209075763950909784148142018992367290485890072303179512881131769414783097454103103347826517701720263541869335631166977965013552647906729408522950996105479525445916501155305220090853891226367184989434453290788068397817927893708837722255115237672194162924260945492012622891770365546831236789867922136747819364833843397165107825773447549885351449899330007200651144003961228091210630807333236718793283427788965479074476288255387824982443633190938302785760754436525586544523339170400053128503337395428393881357669568532722167493096151221381017320147344991331421789379785964440840684363041795410525097564979585773948558651896834067324427900848255265001498890329859444233861478388742393060996236783742654761350763876989363052609107226398858310051497856931093693697981165801539060516895227818925342535261227134364063673285588256280386915163875872231395348293505967057794409379709079685798908660258077792158532257603211711587587586356431658240229896344639704");
if (total.setScale (0, RoundingMode.DOWN).equals (total.setScale (0, RoundingMode.DOWN)))
{
System.out.println ("Success!");
} else
{
throw new Exception ("Fail :(");
}
}
}
---------- END SOURCE ----------